Revista Australiana de Ortodoncia (1)

ContentsOriginal articles1 The dimensions of the roots of the human permanent dentition as a guide to the selection of optimal orthodontic forces

Brian Lee10 Amorphous calcium phosphate-containing orthodontic composites. Do they prevent demineralisation around orthodontic

brackets?Tancan Uysal, Mihri Amasyali, Alp Erdin Koyuturk, Suat Ozcan and Deniz Sagdic

16 Cytotoxicity of orthodontic separating elasticsMatheus Melo Pithon, Rogério Lacerda dos Santos, Fernanda Otaviano Martins, Maria Teresa Villela Romanos andMônica Tirre de Souza Araújo

21 Porcelain brackets during initial alignment: are self-ligating cosmetic brackets more efficient?Peter Miles and Robert Weyant

27 Display of the incisors as functions of age and genderAndrea Fonseca Jardim da Motta, Margareth Maria Gomes de Souza, Ana Maria Bolognese, Clarice Júlia Guerraand José Nelson Mucha

33 McNamara norms for Turkish adolescents with balanced faces and normal occlusionNihat Kilic, Gülhan Catal and Hüsamettin Oktay

38 Assessment of slot sizes in self-ligating brackets using electron microscopyNidhi B. Bhalla, Sarah A. Good, Fraser McDonald, Martyn Sherriff and Alex C. Cash

42 Space planning sensitivity and specificity: Royal London Space Planning and Korkhaus AnalysesRania Dause, Martyn Cobourne and Fraser McDonald

49 Response of the expanded inter-premaxillary suture to intermittent compression. Early bone changesTancan Uysal, Huseyin Olmez, Mihri Amasyali, Yildirim Karslioglu, Atilla Yoldas and Omer Gunhan

56 Associations between upper lip activity and incisor positionNihat Kilic

61 Effects of levelling of the curve of Spee on the proclination of mandibular incisors and expansion of dental arches: a prospective clinical trialNikolaos Pandis, Argy Polychronopoulou, Iosif Sifakakis, Margarita Makou and Theodore Eliades

66 A comparison of dental changes produced by mandibular advancement splints in the management of obstructive sleepapnoeaHui Ching Ang and Craig Dreyer

73 Does ozone water affect the bond strengths of orthodontic brackets?Matheus Melo Pithon and Rogerio Lacerda dos Santos

78 Incremental effects of facemask therapy associated with intermaxillary mechanicsGuilherme Thiesen, Juliana de Oliveira da Luz Fontes, Michella Dinah Zastrow and Naudy Brodbeck May

84 Bond strengths of different orthodontic adhesives after enamel conditioning with the same self-etching primerRogelio J. Scougall-Vilchis, Chrisel Zárate-Díaz, Shusuke Kusakabe and Kohji Yamamoto

Case report90 Multidisciplinary treatment of a fractured root: a case report

Osmar Aparecido Cuoghi, Álvaro Francisco Bosco, Marcos Rogério de Mendonça, Pedro Marcelo Tondelli andYésselin Margot Miranda-Zamalloa

Editorial95 Can an optimal force be estimated?

Michael Harkness

General97 Book reviews 107 Calendar102 Research reviews 108 ASO Directory106 New products

AustralianOrthodontic JournalVolume 26 Number 1, May 2010

Australian Orthodontic Journal Volume 26 No. 1 May 2010

Introduction

In 1952 Storey and Smith showed that orthodonticforces above a certain level produced lower rates oftooth movement than forces below that level.1They named the lower forces ‘optimal’ forces. Thisdefinition has been extended to include the proviso oflittle or no permanent damage to the root and/or the tissues surrounding the root. Importantly, it wassuggested that it was the pressure exerted by the root on the surrounding tissues rather than the actualnumeric value of the force that was a critical factor intooth movement.1 Almost coincidentally, Begg pub-lished results of cases with dramatically short treat-ment times treated entirely by using round wires withsmall cross-sectional areas which seemed to supportthe notion of differential force, which is the use oflight and heavy forces to control the speed of toothmovement.2

Various authors have investigated root dimensionssuch as the surface area;3–12 root volume,13,14 the relation between root length and crown diameter14

and the projected area of the roots,15,16 that may beimportant for tooth movement. It has been arguedthat the relative size of the root(s) may indicate atooth’s resistance to an orthodontic force or theanchorage value.17 High forces are required to moveteeth with large root surface areas. If it were possibleto determine the optimal force levels for tooth move-ment prior to the commencement of treatment,appliances would function with greater efficiency.Our attention was thus focused on the areas of theroots of the permanent dentition.

In this study the lengths, widths and projected areasof the roots of the upper and lower permanent teeth,including the third molars, were measured. Ourintention was to gain an insight into the relations

© Australian Society of Orthodontists Inc. 2010 Australian Orthodontic Journal Volume 26 No. 1 May 2010 1

The dimensions of the roots of the human permanent dentition as a guide to the selection of optimal orthodontic forces

Brian LeeBonnet Hill, Tasmania, Australia

Background: The dimensions of the roots of the teeth are important in the assessment of orthodontic anchorage and to estimatethe forces to be used during orthodontic tooth movement. Aims: To investigate the relations between the lengths, widths and projected areas of the roots of the permanent teeth.Methods: Intact, extracted human permanent teeth were photographed and the lengths, widths and projected areas of selectedsurfaces measured. Descriptive statistics and associations between selected linear dimensions and root areas were calculated.Results: The data showed significant kurtosis and skewness. Neither exponential nor polynomial transformations improved thegoodness of fit, and there was no a priori reason to use other than linear regression. When the lengths of all teeth were multiplied by the respective widths of the mesial, distal and lingual surfaces, the correlations between the product of length andwidth and area improved in 28 out of 30 surfaces. In the lower arch the correlation coefficients ranged from r = .343 (mesialsurface first premolar) to r = .845 (mesial surface of the canine). The correlations in the upper arch ranged from r = .201(mesial surface of the second molar) to r = .847 (mesial surface lateral incisor).Conclusions: For clinical purposes, root length may be an acceptable indicator of root area. Low correlations were attributed tovariations in root shape.(Aust Orthod J 2010; 26: 1–9)

Received for publication: January 2009Accepted: February 2010

Brian Lee: [email protected]

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Table I. Upper teeth, lengths and projected areas of selected surfaces.

Surface Tooth N Minimum Q25 Median Q75 Maximum r R2

Distal length (cm) 1 32 1.10 1.38 1.50 1.57 1.65 .714 0.5112 32 1.36 1.50 1.61 1.68 1.84 .762 0.5813 32 1.20 1.56 1.83 1.95 2.05 .838 0.7024 30 1.04 1.28 1.39 1.49 1.73 .715 0.5125 27 0.98 1.28 1.36 1.46 1.59 .611 0.3736 31 0.80 1.13 1.23 1.29 1.54 .524 0.2747 32 0.90 1.16 1.27 1.39 1.72 .299 0.090

Distal area (cm2) 1 32 0.43 0.60 0.65 0.70 0.822 32 0.56 0.66 0.71 0.77 0.883 32 0.62 0.82 0.98 1.06 1.544 30 0.64 0.74 0.83 0.89 1.155 27 0.48 0.66 0.72 0.77 0.936 31 1.18 1.47 1.54 1.66 2.087 32 0.69 1.00 1.12 1.26 1.62

Lingual length (cm) 1 32 1.08 1.20 1.28 1.37 1.48 .499 0.2492 32 1.12 1.20 1.32 1.43 1.59 .731 0.5353 32 1.08 1.49 1.66 1.80 1.90 .746 0.557

Lingual area (cm2) 1 32 0.42 0.45 0.50 0.56 0.702 32 0.32 0.38 0.45 0.49 0.623 32 0.34 0.56 0.60 0.64 0.84

Mesial length (cm) 1 32 1.09 1.41 1.53 1.64 1.74 .803 0.6452 32 1.29 1.50 1.59 1.73 1.86 .847 0.7173 32 1.20 1.69 1.87 1.99 2.20 .566 0.3204 30 1.08 1.29 1.36 1.49 1.71 .713 0.5085 27 1.00 1.30 1.39 1.45 1.61 .558 0.3126 31 1.06 1.22 1.34 1.41 1.66 .730 0.5337 32 1.06 1.20 1.25 1.38 1.62 .201 0.0408 12 0.83 0.93 0.99 1.10 1.15 .456 0.208

Mesial area (cm2) 1 32 0.50 0.59 0.67 0.74 0.852 32 0.54 0.65 0.69 0.74 0.863 32 0.61 0.97 1.00 1.09 1.834 30 0.48 0.73 0.85 0.94 1.135 27 0.48 0.70 0.74 0.79 0.966 31 1.10 1.56 1.68 1.81 2.347 32 0.84 1.14 1.23 1.31 1.758 12 0.77 0.97 1.19 1.27 1.36

ROOT DIMENSIONS AS A GUIDE TO 0PTIMAL ORTHODONTIC FORCES

Australian Orthodontic Journal Volume 26 No. 1 May 2010 3

Table II. Lower teeth, lengths and projected areas of selected surfaces.

Surface Tooth N Minimum Q25 Median Q75 Maximum r R2

Distal length 1 30 1.16 1.31 1.39 1.47 1.68 .441 0.1952 25 1.20 1.34 1.48 1.57 1.73 .518 0.2693 26 1.44 1.61 1.74 1.79 2.17 .835 0.6964 39 1.16 1.44 1.50 1.60 2.00 .375 0.1415 23 1.21 1.42 1.60 1.64 1.79 .485 0.2366 27 0.86 1.19 1.26 1.39 1.70 .608 0.377 27 1.00 1.12 1.20 1.37 1.60 .820 0.672

Distal area 1 30 0.46 0.53 0.57 0.61 0.762 25 0.48 0.58 0.62 0.68 0.843 26 0.64 0.80 0.97 1.12 1.514 39 0.67 0.85 1.02 1.20 1.535 23 0.64 0.70 0.76 0.80 0.956 27 0.98 1.30 1.40 1.50 2.247 27 0.71 1.10 1.30 1.50 1.71

Lingual length 1 33 1.02 1.18 1.28 1.37 1.65 .529 0.2772 47 1.10 1.32 1.40 1.48 1.60 .665 0.4423 28 1.36 1.61 1.67 1.77 2.01 .717 0.514

Lingual area 1 33 0.22 0.27 0.29 0.38 0.482 47 0.26 0.31 0.34 0.37 0.513 28 0.49 0.61 0.64 0.74 0.93

Mesial length 1 33 1.31 1.34 1.42 1.51 1.75 .566 0.3212 19 1.20 1.45 1.57 1.60 1.78 .594 0.3533 22 1.40 1.68 1.78 1.94 2.30 .845 0.7144 39 1.16 1.41 1.48 1.56 2.04 .343 0.1185 23 1.17 1.45 1.58 1.60 1.84 .582 0.3386 27 1.16 1.26 1.40 1.48 1.78 .807 0.6517 27 1.02 1.08 1.30 1.41 1.55 .812 0.6618 12 1.03 1.28 1.35 1.39 1.73 .554 0.307

Mesial area 1 33 0.53 0.57 0.63 0.67 0.882 19 0.54 0.60 0.64 0.70 0.923 22 0.64 0.80 0.96 1.11 1.574 39 0.66 0.82 1.02 1.15 1.535 23 0.48 0.70 0.80 0.83 1.066 27 1.11 1.32 1.46 1.55 2.337 27 0.87 1.11 1.38 1.50 1.888 12 0.65 0.70 0.83 1.03 1.50

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between the lengths and widths to the areas of corresponding root surfaces in the hope that thisinformation may be of value to clinicians planningorthodontic anchorage and selecting appropriateforces for tooth movement.

Materials and methods

Measurements were made of the root surfaces ofapproximately 580 extracted human permanentteeth, including the third molars. Intact and fullyformed permanent teeth were collected in the period1963–65 and measured using the methods describedbelow. The age, gender and ethnicity of the subjectswere not recorded.

The teeth were cleaned of attached soft tissue, dried,labelled and numbered. Multi-rooted teeth were sec-tioned through the furcation(s) in order to obtain aclear view of the root surfaces and each root was pho-tographed and measured separately. The four surfacesof the teeth (mesial, distal, buccal, lingual) were photographed alongside a metric rule. The film planewas parallel to the long axis of each tooth. The photo-graphic images were enlarged x10 and the outline ofeach root surface traced on paper. The lengths andwidths of the roots were measured on the tracings.The length of the proximal surface of a root was thedistance from the root apex to the peak of the curveof the cemento-enamel junction on the proximal sur-face, and the length of a lingual surface was the distance from the apex to the lowest point on thecurve of the cemento-enamel junction. Root widthwas measured at the cemento-enamel junction. The dimensions of the same surfaces were added.Data for corresponding right and left teeth were combined.

The area of each root surface was then measureddirectly with a planimeter (Allbrit 37595 Fixed Armplanimeter, Stanley, London, UK). The accuracy ofthe planimeter was tested before use by tracing a circle using the radius arm provided with the instru-ment to determine if the area of the traced circle coincided with the nominated area. Before analysis,the planimeter measurements were converted to theactual sizes by dividing the linear measurements by10 and the area measurements by 100. All linear andwidth measurements are in centimetres (cm) and theareas in centimetres squared (cm2).

Descriptive statistics and skewness and kurtosis werecalculated for the distal, mesial and lingual lengths,

widths and projected areas of the upper and lowerteeth. Pearson’s correlation coefficients and regressionequations between the lengths and projected areas ofcorresponding root surfaces, and associations betweenroot length and the calculated area (the product oflength and width) to the projected area of correspon-ding surfaces were also calculated for teeth with widthand length measurements.

Results

The results are given in Tables I and II and Figures 1and 2. The tables contain the sample sizes, minimumand maximum values, quartile values, medians, corre-lations of length to the projected areas of selected per-manent teeth and coefficients of determination (R2

values). The measured and calculated values of thevarious surfaces of selected upper and lower teeth areshown in Figure 1. Regression lines of the relationsbetween projected root length and area of the distal,mesial and lingual surfaces of the upper and lowerteeth are given in Figure 2.

The median length of the distal surface of the uppercentral incisor root was 1.50 cm and for the uppercanine it was 1.83 cm (Table I). The median areas ofthe distal surfaces of the upper canine and first molarwere 0.98 and 1.54 cm2, respectively. The palatal sur-face of the upper lateral incisor (Median: 1.32 cm)was slightly longer than that of the upper central inci-sor (Median: 1.28 cm), but shorter than the uppercanine (Median length: 1.66 cm). The median areasof the palatal surfaces of the upper central incisor,upper lateral incisor and upper canine were 0.50,0.45 and 0.60 cm2, respectively. Although the mesialsurface of the upper first molar was shorter than allother teeth in the upper arch except the second andthird molars, it had the largest mesial area (Median:1.68 cm2). The mesial areas (medians) of all upperteeth were larger than the distal areas (medians) ofcorresponding teeth, except for the lateral incisors.

The canine was the longest tooth in the lower arch,but the areas of the mesial and distal root surfaces(Distal surface area median: 0.97 cm2; Mesial surfacearea median: 0.96 cm2) were less than the corres-ponding areas (Distal area median: 1.40 cm2; Mesialarea median: 1.46 cm2) of the first molar (Table II).The distal surface of the lower first premolar wasshorter than the same surface of the canine, but themedian area of the distal surface of the first premolarwas greater than the median area of the canine.



Length: y = 1.1851x + 0.6068 R2 = 0.7022Width: y = 0.1838x + 0.6022 R2 = 0.3644Calculated area: y = 1.273x + 0.1395 R2 = 0.8378

(a) Upper canine distal.

Length

Width

Calculated

2.5

2

1.5

1

0.5

00 0.5 1 1.5 2 2.5

Measured area cm2

Length: y = 0.7085x + 0.8334 R2 = 0.3119Width: y = 0.9536x + 0.369 R2 = 0.6159 Calculated area: y = 0.3104x + 0.5616 R2 = 0.3256

(d) Upper second premolar mesial.

Length

Width

Calculated

2.5

2

1.5

1

0.5

00 0.5 1 1.5 2 2.5

Measured area cm2

Length: y = 0.5239x + 0.465 R2 = 0.533Width: y = 0.2651x + 0.6938 R2 = 0.3841Calculated: y = 0.9501x + 0.0614 R2 = 0.7864

(e) Upper first molar mesial.

2.5

2

1.5

1

0.5

00 0.5 1 1.5 2 2.5

Measured area cm2


(f) Lower canine distal.

LengthWidthCalculated

2.5

2

1.5

1

0.5

00 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Measured area cm2

Figure 1. Plots derived from raw data. Individual data are indicated and regression lines for length, width and calculated area (length x width) with the projected(measured) area are given.

Length

Leng

th/W

idth

/Cal

cula

ted

area

(cm

/cm

/cm

2 )

Leng

th/W

idth

/Cal

cula

ted

area

(cm

/cm

/cm

2 )Le

ngth

/Wid

th/C

alcu

late

d ar

ea(c

m/c

m/c

m2 )

Leng

th/W

idth

/Cal

cula

ted

area

(cm

/cm

/cm

2 )

1.6

1.4

1.2

1

0.8

0.6

0.4

0.2

00 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Calculated area cm2

Length: y = 0.7647x + 0.8948 R2 = 0.2495

(b) Upper central incisor lingual.

Length1.8

1.6

1.4

1.2

1

0.8

0.6

0.4

0.2

00 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Measureed area cm2

Length: y = 1.2694x + 0.7516 R2 = 0.5349

(c) Upper lateral incisor lingual.

LengthWidthCalculated

Leng

th/W

idth

/Cal

cula

ted

area

(cm

/cm

/cm

2 )

Leng

th/W

idth

/Cal

cula

ted

area

(cm

/cm

/cm

2 )

In the upper arch, the coefficients range from .847between the length and area of the mesial surface ofthe lateral incisor to .201 between the length and areaof the mesial surface of the second molar. The corre-lation coefficient between the distal surface and distalarea of the upper canine was .838 and between thelength and area of the mesial facing root surfaces ofthe upper first molar it was .730. In the lower arch,the coefficients for the distal surface of the canine andthe mesial surface of the first molar were .835 and.807, respectively.

There was significant kurtosis and skewness in thedata (more than two standard deviations) indicatingthat the distributions were not normal, but there wasno apparent relationship between skewness and thecoefficients of determination, nor was there any con-sistency in the sense or direction of the skew.However, neither exponential nor polynomial trans-formations improved the goodness of fit, and there isno a priori reason to use other than linear regression.Coefficients of determination (R2) for selected teethare given in Tables I and II. The coefficient of deter-mination indicates the degree to which the variationamongst projected areas can be accounted for by rootlength.

When the lengths of the upper teeth were multipliedby the respective widths the correlations with the cor-responding root surface lengths increased in 28 of 30surfaces. Only the correlations between the lengthsand calculated areas of the distal surfaces of the upperfirst and second molars, and the mesial lengths andcalculated areas of the lower lateral incisor and distalsurface of the lower central incisor did not improve.

DiscussionThis study set out to determine if clinically usefulassociations existed between the lengths and areas ofthe roots of the upper and lower teeth, however laterin the study, root width was included to determinewhether that dimension was of any value in estimat-ing projected area. A strong association (>.8) wouldenable a clinician to use the product of root lengthand width as a predictor of root area and select anappropriate force to obtain optimal tooth movementand/or estimate the anchorage value of a tooth orgroup of teeth.

The coefficients for the distal surfaces of the uppercanines and the mesial surfaces of the lower firstmolars accounted for approximately 70 and 65 percent of the variations in root area, respectively, whenthe root lengths were known. The coefficients ofdetermination were relatively high for several otherteeth, notably the mesial surfaces of the upper lateralincisor and the lower first and second molars. Thecoefficient of determination for the lingual surface ofthe upper central incisor was only .249, possiblybecause an incisor with a short, wide root can havethe same area as one with a long, slender root. For theupper central incisor, root length alone is not a goodpredictor of root area. We succeeded in improving thepredictability of root length by using a calculated area(length x width) in our calculations. Data for thesecalculations are available on the Journal website. In all but two cases, this quantity accounted for morevariance than using length alone.

Estimation of optimal forces needs to take intoaccount teeth with unusual variations in the axes of

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Length: y = 0.657x + 1.0277 R2 = 0.3383

(g) Lower second premolar mesial.

Length2

1.81.61.41.2

10.80.60.40.2

00 0.2 0.4 0.6 0.8 1 1.2

Measured area


(h) Lower first molar mesial.

Length

Width

Calculated

21.81.61.41.2

10.80.60.40.2

00 0.5 1 1.5 2 2.5

Measured area cm2

Figure 1 (Continued). Plots derived from raw data. Individual data are indicated and regression lines for length, width and calculated area (length x width) with theprojected area are given.

Leng

th/W

idth

/Cal

cula

ted

area

(cm

/cm

/cm

2 )

Leng

th/W

idth

/Cal

cula

ted

area

(cm

/cm

/cm

2 )



Upper 1Upper 2Upper 3Upper 4Upper 5Upper 6Upper 7

Dis

tal a

rea

(cm

2 )

2.5

2

1.5

1

0.5

00 0.5 1 1.5 2 2.5

Distal length (cm)

Upper 1Upper 2Upper 3Upper 4Upper 5Upper 6Upper 7Upper 8

Mes

ial a

rea

(cm

2 )

2.5

2

1.5

1

0.5

00 0.5 1 1.5 2 2.5

Mesial length (cm)

Lower 1

Lower 2

Lower 3

Lower 4

Lower 5

Lower 6

Lower 7

Dis

tal a

rea

(cm

2 )

2.5

2

1.5

1

0.5

00 0.5 1 1.5 2 2.5

Distal length (cm)

Lower 1Lower 2Lower 3Lower 4Lower 5Lower 6Lower 7Lower 8

Mes

ial a

rea

(cm

2 )

2.5

2

1.5

1

0.5

00 0.5 1 1.5 2 2.5

Mesial length (cm)

Lower 1

Lower 2

Lower 3

Ling

ual a

rea

(cm

2 )

2.5

2

1.5

1

0.5

00 0.5 1 1.5 2 2.5

Lingual length (cm)

Upper 1

Upper 2

Upper 3

Ling

ual a

rea

(cm

2 )

2.5

2

1.5

1

0.5

00 0.5 1 1.5 2

L:ingual length (cm)

(a) Regression lines showing the relations between distal lengths and areasfor the upper teeth.

(f) Mesial lengths and areas for the lower teeth.

(c) Mesial lengths and areas for the upper teeth.

(e) Lingual lengths and areas for the lower teeth.

(d) Distal lengths and areas for the lower teeth.

(b) Lingual lengths and areas for the upper teeth.

Figure 2. Regression lines for the length and areas of the upper and lower teeth.

the crowns and roots and/or root bends or curves.18,19

Also the shape of the cemento-enamel junction on aproximal surface varies according to the labio-lingualwidth of the root.18 In a wide tooth the curve of thecemento-enamel junction has a somewhat flattenedshape, whereas in a narrow tooth the junction issomewhat angular in shape.

Limitations in this study that should be consideredare our methods of measuring length and area: bothmeasurements were made parallel to the long axis ofthe root and were influenced to a certain degree by the angle between the root surface and the longaxis of the tooth, and the shape of the root. Some teeth had pyramidal roots and other teeth hadcurved roots. These variations, although small, maycontribute to the variability in tooth movementencountered by a clinician using root length to estimate root area and an optimal force. For someteeth the projected length, for example of the upperlateral incisor, would be less than the actual length.When, however, the width (at right angles to the rootsurface of interest) and the projected length of a rootare known, the actual length of the root can be cal-culated. Bucco-lingual widths are difficult to measure using traditional radiographs. To overcomethis, we designed a caliper to measure the width at the cemento-enamel junction and have used thisinstrument to estimate projected areas and haveobtained results consistent with other workers (Figure 3).16,20,21 Finally, the strengths of this studyare the size of the samples and our use of teeth withfully developed roots.

How can the results be applied to estimate the optimum force for tooth movement or anchorage? To

use the graphs, first decide on a treatment plan andthe directions of tooth movement. Estimate the rootlength of a particular tooth from a radiograph orfrom an already extracted tooth and use the appro-priate regression line to obtain an estimate of rootarea. As the mean peak velocity of movement of thecanines in both humans and dogs occurred when amean pressure of 200 cN/cm-2 was exerted, multiplythis estimated area by 200 (as force equals pressure xarea) to determine the force required.20 When thisfigure is applied to the median projected area of thedistal surface of the upper canine (0.98 cm2) themean optimum pressure is 196 cN/cm-2. Thisapproximates reported estimates of 197 cN/cm-2

based on experimental data from humans.1,16,21,22

Using this approach it is now possible to estimate theforces required to obtain optimal rates of tooth move-ment and, by using higher forces, a stable anchorunit. Eventually, other root dimensions, such as volume and bone density may improve estimates of atooth’s resistance to orthodontic movement than eitherroot length or the product of root length and width.12,13

Conclusions

The following conclusions were drawn:

1. For clinical purposes, root length may be anacceptable indicator of root area.

2. The product of root length and width resulted inhigher coefficients of determination. A method ofmeasuring bucco-lingual width is described.

2. Low correlations between root length and areawere attributed to variations in root shape.

Acknowledgments

I would like to thank Professor Shen Gang for hisassistance in collating the data for this study andDesmond Fitzgerald and Geoffrey Fenn for theirassistance with the statistics and my wife Joanna forhelp with the preparation of this report.

Corresponding author

Dr Brian W. Lee3 Lynden RoadBonnet Hill, Tasmania 7053AustraliaTel: (+61 3) 6229 9468Email: [email protected]

LEE


Figure 3. Caliper designed to measure tooth dimensions at the cemento-enamel junction.

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15. Garn SM, Van Alstine WL Jr, Cole PE. Relationshipbetween root lengths and crown diameters of correspondingteeth. J Dent Res 1978;57:636.

16. Lee BW. The force requirements for tooth movement. PartIII: The pressure hypothesis tested. Aust Orthod J 1996;14:93–7.

17. Chen SK, Pan JH, C CM, Jeng JY. Accuracy of supportedroot ratio estimation from projected length and area usingdigital radiographs. J Periodontol 2004;75:866–71.

18. Taylor RMS. Variation in form of human teeth: I. Ananthropologic and forensic study of maxillary incisors. JDent Res 1969; 48:5–16.

19. Taylor RMS. Variation in form of human teeth: I. Ananthropologic and forensic study of maxillary canines. JDent Res 1969; 48:173–82.

20. Ren Y, Maltha J, Van’t Hof MA, Kuijpers-Jagtman AM.Optimum force magnitude for orthodontic tooth move-ment: a systematic literature review. Am J OrthodDentofacial Orthop 2004;125:71–7.

21. Lee BW. The force requirements for tooth movement. Part I:Tipping and bodily movement. Aust Orthod J 1995;13:238–48.

22. Smith R, Storey E. The importance of force in orthodontics.Design of cuspid retraction springs. Aust J Dent 1952;56:291–304.



IntroductionPoor oral hygiene following placement of a bondedorthodontic appliance can result in unsightly whitespot lesions on the labial surfaces of the anteriorteeth.1,2 Although a white spot lesion is the first visi-ble sign of enamel softening, measurable deminerali-sation can occur around orthodontic brackets as earlyas one month after an appliance has been placed.3–6

Overall management of white spot lesions involvesmethods of both preventing demineralisation andencouraging remineralisation of existing lesions.7 The

former includes good oral hygiene and the latter mayinclude the application of materials, such as caseinphosphopeptide – amorphous calcium phosphatenano-complexes (CPP-ACP) that enhance remineral-isation of enamel.8 A recent development has beenthe addition of amorphous calcium phosphate (ACP)to orthodontic composites with the intention ofenhancing enamel remineralisation around bondedbrackets. This area is particularly prone to deminer-alisation because plaque readily accumulates onorthodontic composites.

Australian Orthodontic Journal Volume 26 No. 1 May 2010 © Australian Society of Orthodontists Inc. 201010

Amorphous calcium phosphate-containing orthodontic composites. Do they prevent demineralisation around orthodontic brackets?

Tancan Uysal,* Mihri Amasyali,† Alp Erdin Koyuturk,+ Suat Ozcan,±

and Deniz Sagdic†

Department of Orthodontics, Erciyes University, Kayseri, Turkey and King Saud University, Riyadh, Saudi Arabia,* Department ofOrthodontics, Gülhane Military Medical Academy, Ankara, Turkey,† Department of Pediatric Dentistry, Ondokuz Mayis University, Samsun,Turkey,+ and the Department of Conservative Dentistry and Endodontics, Gazi University, Ankara, Turkey±

Background: A preliminary study using laser fluorescence suggested that amorphous phosphate-containing orthodontic composites may prevent demineralisation around bonded orthodontic brackets. Objective: To compare the microhardness of the enamel around brackets bonded with an amorphous calcium phosphate-containing orthodontic composite (ACP-containing) with the microhardness of the enamel around brackets bonded with a conventional composite resin.Methods: Forty extracted upper premolars were used. Orthodontic brackets were bonded to the teeth with either an ACP-containing composite resin (N = 20) or a conventional composite resin (N = 20). The latter were used as the control. Thecrowns of all teeth were painted with an acid resistant varnish, leaving a 2 mm ring of exposed enamel around the brackets.The teeth were then subjected to a daily cycle of demineralisation for 6 hours and remineralisation for 18 hours for 21 days.Each tooth was sectioned and the microhardness of the enamel determined 25, 50, 75, 100 and 150 µm from the surface.Results: The enamel was significantly harder 25 µm (p = 0.000) and 50 µm (p = 0.001) from the enamel surface in the teethwith brackets bonded with the ACP-containing composite resin as compared with the control teeth.Conclusion: ACP-containing orthodontic composite resins may reduce the enamel decalcification found in patients with poororal hygiene.(Aust Orthod J 2010; 26: 10–15)

Received for publication: April 2009Accepted: July 2009

Tancan Uysal: [email protected] Amasyali: [email protected] Koyuturk: [email protected] Ozcan: [email protected] Sagdic: [email protected]

DO ACP-CONTAINING COMPOSITE RESINS PREVENT DEMINERALISATION?


In a preliminary study we used a laser fluorescencedevice to compare ‘enamel demineralisation’ aroundorthodontic brackets bonded with either an ACP-containing composite or a resin-modified glassionomer cement.9 We found that ACP-containingorthodontic composites provided the highest reduc-tions in enamel demineralisation when comparedwith a resin-modified glass ionomer cement and thecontrol. However, Diniz et al. recently reported thatlaser fluorescence devices for detecting in-vitro demineralisation are unreliable.10 Thus, we decidedto determine the extent of demineralisation aroundorthodontic brackets bonded with either an ACP-containing composite resin or a conventional composite resin by measuring enamel microhardness:one of the traditional methods of determining earlydemineralisation.4–6,10 The method, which has beenwidely used in caries research, correlates deminerali-sation with microhardness.4

The aim of this in-vitro study was to compare themicrohardness of the enamel around brackets bondedwith an amorphous calcium phosphate-containingorthodontic composite (ACP-containing) with theenamel around brackets bonded with a conventionalcomposite resin after the teeth had been exposed toacid attack.

Materials and methodsPreparation of the teethForty caries-free human upper premolars, extractedfor orthodontic reasons, were used in this study.Before use the teeth were stored in 0.1 per cent thymol for periods no longer than one month. Teethwith hypoplastic areas, cracks and/or gross irregulari-ties of enamel structure or treated with chemicalagents such as alcohol, formalin or hydrogen per-oxide were excluded from the study. Soft tissue rem-nants and calculus were removed from the teeth andthe crowns cleaned with fluoride-free pumice and arubber cup. The teeth were then stored in StreckTissue Fixative (Streck Laboratories, Inc., Omaha,NE, USA) for two weeks. This solution has anantimicrobial action and does not compromise histo-logical examination of the enamel following artificialdemineralisation.11 The teeth were randomly distrib-uted into the control (Group 1) and the experimentalgroup (Group 2) equally. The buccal surface of eachpremolar was etched with 37 per cent ortho-phosphoric acid gel (3M Dental Products, St. Paul,

MN, USA) for 15 seconds, rinsed with water for 15seconds and dried with oil-free air for 10 secondsuntil the enamel appeared frosty-white.

In Group 1, Transbond XT primer (3M Unitek,Monrovia, CA, USA) was applied to the etched sur-face in a thin film and not cured. Transbond XT com-posite paste was applied to the base of the stainlesssteel bracket (Dyna-Lok series, 100-gauge mesh, 3MUnitek, USA). Each bracket was positioned at themaximum contour mesio-distally in the middle onethird of the buccal surface occluso-gingivally and parallel to the long axis of the tooth, and pressedfirmly into place. The excess composite was removedwith a scaler.

In Group 2, a thin layer of ACP-containing ortho-dontic composite (Aegis Ortho, Harry J BosworthCo., IL, USA) was applied to the etched enamel andthe base of the bracket. The bracket was pressed ontothe buccal surface of the tooth in an identical positionto that used in Group 1. Following the manufac-turer’s recommendations, excess composite was notremoved.

A light-emitting diode curing unit (Elipar Freelight 2,3M-ESPE, St. Paul, MN, USA) was applied to themesial and distal edges of the brackets in both groupsfor 10 seconds per side (Total time: 20 seconds).Following curing, the crowns of the teeth were paint-ed with an acid-resistant varnish, leaving a 2 mm ringof exposed enamel around the brackets. The speci-mens were stored in 100 per cent humidity for 12hours at 37 °C.

Demineralisation procedureThe baseline mineralisation of the enamel aroundeach bracket was measured with a portable battery-powered laser fluorescence device (Diagnodent Pen,KaVo, Germany). The scores in both groups were under 13, indicating that the enamel was notdemineralised and all teeth had the same risk of caries(Figure 1).

The demineralisation procedure was adapted fromthe method described by Hu and Featherstone.12 Thedaily procedure of pH cycling included a deminerali-sation period of 6 hours (0900–1500 hours) and aremineralisation period of 18 hours (1500–0900hours). The crown of each tooth was immersed in 60mL of demineralisation solution containing 2.0mmol/L calcium, 2.0 mmol/L phosphates, and 75

mmol/L acetate at pH 4.3 for 6 hours at 37 °C.Specimens were then removed from the demineralisa-tion solution, rinsed with deionised water andimmersed in 40 mL of the remineralisation solutionat 37 °C overnight (18 hours), to simulate the rem-ineralising stage of the caries process. The reminerali-sation solution consisted of 1.5 mmol/L calcium, 0.9mmol/L phosphates, 150 mmol/L potassium chlo-ride, and 20 mmol/L cacodylate buffers at pH 7.0.This cycling procedure was repeated daily for 21 days.On day 21, the presence of demineralised enamel wasconfirmed with the laser fluorescent device and, visu-ally, the enamel appeared frosty-white when the teethwere dried. The teeth were removed from the solutionand the brackets removed.

Microhardness analysisThe roots of the teeth were removed with a water-cooled diamond disk. The crowns were hemi-sectioned vertically into mesial and distal halves witha large 15 HC wafering blade in an Isomet low-speedsaw (Buehler, Lake Bluff, IL, USA). The hemi-sections were cut into a cervical portion and anocclusal portion. Both portions were embedded inself-curing epoxy resin (Epo-Kwick, Buehler, Lake

Bluff, IL, USA), leaving the cut face exposed. Thehalf crown sections were polished with abrasive paperdiscs (320, 600, and 1200 grit) and polished with a 1 µm diamond spray and a cloth polishing disc(Buehler, Lake Bluff, IL, USA). A microhardnesstester (HMV-700, Shimadzu, Kyoto, Japan) under a2N load for 15 seconds was used for the microhard-ness analysis. In the occlusal and cervical regions,indentations were made at the edge (0 µm) of thecomposite and 25, 50, 75, 100, 125, and 150 µmfrom the external surface of the enamel.

Statistical analysisData analysis was performed by using StatisticalPackage for Social Sciences, (SPSS, Vers.13.0, SPSSInc. Chicago, IL, USA) and Excel 2000 (MicrosoftCorporation, Redmond, WA, USA). Descriptive statistics were calculated for both groups. TheShapiro-Wilks normality test and Levene’s variancehomogeneity test were applied to the microhardnessdata. The data were normally distributed and therewas homogeneity of variances between the groups.Occlusal and cervical microhardness scores at thesame depths in matching half crown specimens werecompared with the paired t-test. Student’s t-test wasused to compare the effect of the materials(Transbond XT and Aegis Ortho) 25, 50, 75, 100,125, and 150 µm from the enamel surface. For multiple comparisons, the analysis of variance(ANOVA) and Tukey Honestly Significant Differ-ence (HSD) post-hoc test were used. A significancelevel of p < 0.05 was used for all tests.

To determine the intra- and inter-observer agree-ment, the microhardness of the enamel was measuredby two investigators using the same instrument at twoseparate times, and Cohen’s Kappa scores were determined.

UYSAL ET AL


Figure 1. Measurement of the demineralisation on the occlusal side of the bracket by Diagnodent Pen.

Table I. Intra- and inter-examiner agreement for the microhardnessscores.

Observation Kappa score (K)

Intra-examiner agreement (Examiner 1) 0.83Intra-examiner agreement (Examiner 2) 0.88Inter-observer agreement 0.81

Cohen's Kappa:K < 0.40 poor agreement K = 0.41 - 0.60 moderate agreement K = 0.61 - 0.80 substantial agreement K > 0.80 - almost perfect agreement



Results

The intra- and inter-examiner Kappa scores forassessment of microhardness exceeded 0.80 (Table I).

There were no statistically significant differencesbetween the enamel microhardnesses in the occlusaland cervical sections in each group (p > 0.05). Themean microhardness scores in the Transbond XTgroup (Group 1) increased steadily from 185.80Vickers Hardness Number (VHN) at the 25 µm,234.70 VHN at 50 µm, 253.70 VHN at 75 µm,271.35 VHN at 100 µm, 295.95 VHN at 125 µm to300.50 VHN at 150 µm (Table II). The mean micro-hardness scores in the Aegis Ortho group (Group 2)also increased steadily from 223.35 VHN at 25 µm to302.85 VHN at 150 µm. Although the mean differ-ences between the two groups fell from 37.55 VHNat 25 µm to 2.35 VHN at 150 µm, only the micro-hardness values at the 25 and 50 µm levels were sig-nificantly different. The enamel was significantlyharder in Group 2 (Aegis Ortho) than in Group 1(Transbond XT) 25 and 50 µm from the enamel sur-face. There were no significant group differences inenamel microhardness from 75 to 150 µm from theenamel surface.

The microhardness scores in both groups at the 25and 50 µm were approximately twice as variable asthe microhardness scores at the 75, 100 and 150 µmlevels, but not at the 125 µm level. For example, therange in enamel microhardness 25 µm from the

surface was 49 VHN in the Transbond XT group(Range: 160–209 VHN) and 44 VHN in the AegisOrtho group (Range: 201–245 VHN). Similar varia-tion in the ranges occurred at the 50 µm level.

Discussion

We subjected teeth with stainless steel orthodonticbrackets bonded with either an ACP-containing com-posite resin or a conventional composite resin tocycles of demineralisation and remineralisation andmeasured the microhardness of the enamel surround-ing the brackets. The enamel was significantly harder25 µm and 50 µm from the enamel surface in theteeth with brackets bonded with the ACP-containingcomposite resin, suggesting that ACP-containingcomposite resins may lessen the risk of demineralisa-tion in patients with poor oral hygiene.

In this in-vitro study we attempted to simulate theprocesses of acid attack that occurs beneath plaque invivo and subsequent remineralisation by minerals inthe saliva over 21 days.12,13 Whereas Hu andFeatherstone12 cycled the teeth in their study through demineralisation and remineralisation solu-tions for 14 days, we extended our study to 21 daysbecause we found no visual evidence of demineralisa-tion after 14 days exposure to the solutions. By 21days, however, the enamel surrounding the bracketsin the control group appeared frosty-white whendried.

Table II. Comparisons of enamel microhardness.

Microhardness (VHN)

Depth Composite N Mean SD SEM Minimum Maximum p

25µm Transbond XT 20 185.80 9.95 2.22 160 209 0.000Aegis Ortho 20 223.35 11.03 2.47 201 245






Significant values in bold

We assessed mineral loss from the teeth by deter-mining the microhardness of the enamel at selected depths. This is a proven and widely-usedmethod to determine the loss of mineral that is a feature of early carious lesions. A strong correlation (r = .91) was reported by Featherstone and co-workers between enamel microhardness scores andthe percentage loss of mineral in the carious lesions.13

While others have reported that the demineral-isation of the enamel around orthodontic bracketscan extend as far as 75 µm below the enamel sur-face, Gorton and Featherstone4 and Pascotto et al.5reported that enamel demineralisation extended to only 30 µm from the enamel surface in vivo. They allowed their subjects to brush their teeth which presumably removed some/all of the plaque and micro-organisms responsible for deminer-alisation.

We used a portable battery-powered laser fluores-cence device to determine the levels of mineralisationat the start of the study and after 21 days. Althoughthe device confirmed that the groups had similarbaseline levels of mineralisation at the start of thestudy and that they were demineralised after 21 daysexposure to the solutions, these results should beregarded with caution as it has recently been reportedthat this method of determining the level of mineralisation is unreliable.10

Bioactive materials, such as ACP or CPP-ACP havebeen added to several materials used in dentistry toincrease the concentrations of calcium and phosphateions in dental plaque and replace minerals lost fromthe enamel during the demineralisation process.14–17

CPP-ACP has been added to various products, suchas sugar-free chewing gum, mints, topical gels,mousse, tooth paste, sports drinks and glass ionomercements and remineralisation of already deminer-alised enamel lesions has been reported.8,12,18 Theseinnovations are ideal for the prevention of enameldemineralisation in vivo as the material is in closeproximity to the enamel, and there appears to be aninverse relationship between calcium and phosphatelevels in dental plaque and caries experience.17

Sodium fluoride either alone or in combination withCPP-ACP will also prevent enamel demineralisationadjacent to orthodontic brackets.7 The consensus isthat ACP-containing materials have higher reminer-alising potential than the conventional compositeresins and cements.8,16

Conclusion

ACP-containing orthodontic composite resins mayreduce the enamel decalcification found in patientswith poor oral hygiene.

Acknowledgments

The authors thank Ertan Seçkin of Guney Dental forproviding the Diagnodent Pen and for supportingthis project.


Dr Tancan UysalErciyes UniversitesiDis Hekimligi FacultesiOrtodonti Anabilum Dall, 38039MelikgaziKayseriTurkeyEmail: [email protected]

References1. Smales RJ. Plaque growth on dental restorative materials. J

Dent 1981;9:133–40.2. Vorhies AB, Donly KJ, Staley RN, Wefel JS. Enamel dem-

ineralization adjacent to orthodontic brackets bonded withhybrid glass ionomer cements: an in vitro study. Am JOrthod Dentofacial Orthop 1998;114:668–74.

3. O’Reilly MM, Featherstone JD. Demineralization and rem-ineralization around orthodontic appliances: an in vivostudy. Am J Orthod Dentofacial Orthop 1987;92:33–40.

4. Gorton J, Featherstone JD. In vivo inhibition of demineral-ization around orthodontic brackets. Am J OrthodDentofacial Orthop 2003;123:10–14.

5. Pascotto RC, Navarro MF, Capelozza Filho L, Cury JA. Invivo effect of a resin-modified glass ionomer cement onenamel demineralization around orthodontic brackets. Am JOrthod Dentofacial Orthop 2004;125:36–41.

6. de Moura MS, de Melo Simplício AH, Cury JA. In-vivoeffects of fluoridated antiplaque dentifrice and bondingmaterial on enamel demineralization adjacent to orthodon-tic appliances. Am J Orthod Dentofacial Orthop 2006;130:357–63.

7. Sudjalim TR, Woods MG, Manton DJ, Reynolds EC.Prevention of demineralization around orthodontic bracketsin vitro. Am J Orthod Dentofacial Orthop 2007;131:705e1–9.

8. Kumar VL, Itthagarun A, King NM. The effect of caseinphosphopeptide-amorphous calcium phosphate on reminer-alization of artificial caries-like lesions: an in vitro study.Aust Dent J 2008;53:34–40.

9. Uysal T, Amasyali M, Koyuturk AE, Sagdic D. Efficiency ofamorphous calcium phosphate-containing orthodontic com-posite and resin modified glass ionomer on demineralizationevaluated by a new laser fluorescence device. Eur J Dent2009;3:127–34.

10. Diniz MB, Leme AF, Cardoso KD, Rodrigues JD, CordeiroRD. The efficacy of laser fluorescence to detect in vitro

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demineralization and remineralization of smooth enamelsurfaces. Photomed Laser Surg 2009;27:57–61.

11. Shapiro S, Meier A, Guggenheim B. The antimicrobial activ-ity of essential oils and essential oil components towards oralbacteria. Oral Microbiol Immunol 1994;9:202–8.

12. Hu W, Featherstone JD. Prevention of enamel demineraliza-tion: an in vitro study using light-cured filled sealant. Am JOrthod Dentofacial Orthop 2005;128:592–600.

13. Featherstone JB, ten Cate JM, Shariati M, Arends J.Comparison of artificial caries-like lesion by quantitativemicroradiography and microhardness profiles. Caries Res1983;17:385–91.

14. Dunn WJ. Shear bond strength of an amorphous calcium-phosphate-containing orthodontic resin cement. Am JOrthod Dentofacial Orthop 2007;131:243–7.

15. Uysal T, Ulker M, Akdogan G, Ramoglu SI, Yilmaz E. Bondstrength of amorphous calcium phosphate-containing ortho-dontic composite used as a lingual retainer adhesive. AngleOrthod 2009;79:117–21.

16. Shen P, Cai F, Nowicki A, Vincent J, Reynolds EC.Remineralization of enamel subsurface lesions by sugar-freechewing gum containing casein phosphopeptide-amorphouscalcium phosphate. J Dent Res 2001;80:2066–70.

17. Reynolds EC, Cai F, Shen P, Walker GD. Retention inplaque and remineralization of enamel lesions by variousforms of calcium in a mouthrinse or sugar-free chewinggum. J Dent Res 2003;82:206–11.

18. Rose RK. Binding characteristics of streptococcus mutansfor calcium and casein phosphopeptide. Caries Res 2000;34:427–31.

Introduction

Recent studies have been concerned with the bio-compatibility of different types of orthodontic materials.1,2 Separating elastics made from naturalrubber and non-latex materials are commonly usedprior to orthodontic treatment. Allergic reactionscaused by latex proteins have been well-documented,but little is known if latex and non-latex products arecytotoxic to oral mucosal cells.3–9

Cell lines, such as L-929 mouse fibroblasts, have beenshown to behave similarly to human gingival fibrob-lasts and, therefore, are a suitable in-vitro model totest the toxicity of products used intra-orally during

orthodontic treatment.10–14 The objective of this in-vitro study was to determine if latex and non-latexorthodontic separating elastics are cytotoxic.


Fifteen blue-coloured elastics (Diameter: 4.4 mm)from four manufacturers were assigned to the follow-ing groups: Group M, silicone (non-latex) modularelastics (Masel, Bristol, PA, USA); Group D, naturallatex modular elastics (Dentaurum, Ispringen,Germany); Group A, natural latex bulk pack elastics(Aditek, Cravinhos, São Paulo, Brazil); Group O,natural latex bulk pack elastics (OrthoSource, North


Cytotoxicity of orthodontic separating elastics

Matheus Melo Pithon, Rogério Lacerda dos Santos, Fernanda Otaviano Martins,Maria Teresa Villela Romanos and Mônica Tirre de Souza AraujoFederal University of Rio de Janeiro-UFRJ, Rio de Janeiro, Brazil

Background: Separating elastics may be cytotoxic to the interdental gingival tissues. Both latex and non-latex separating elasticsare widely used and both types should be biocompatible.Objective: To determine if latex and non-latex orthodontic separating elastics are cytotoxic. Methods: The cytotoxicity of natural latex (Groups A, D and O) and non-latex (Group M) orthodontic separating elastics weredetermined by incubating 15 elastics of each type in Eagle’s essential medium (MEM), removing the supernatant after 24, 48,72 and 168 hours and adding it to cultures of L-929 mouse fibroblasts in growth medium (MEM plus glutamine, garamicine,fungizone, sodium bicarbonate, buffered saline and foetal calf serum). To verify the cell response in extreme situations, threeadditional groups were included: Group CC (cell control), consisting of L-929 cells not exposed to supernatants from the main-tenance medium with the elastics; Group C+ (positive control), consisting of Tween 80; Group C- (negative control), consistingof phosphate buffered saline solution. The positive and negative controls were incubated in MEM maintenance medium for 24,48, 72 and 168 hours and the extracted elutes were added to L-929 line cells incubated in the growth medium. The viabilityof the cells was determined with neutral red (dye-uptake method) at 24, 48, 72 and 168 hours. The data were analysed withthe analysis of variance (ANOVA) and Tukey’s multiple comparison test. The significance level was p ≤ 0.05. Results: The elastics in Groups A, D and O induced greater cell lysis at 72 hours compared to the other experimental times.There were statistically significant differences between the cytotoxicity of the elastics in Groups A, D and O in relation to Group CC for experimental times of 24, 48, 72 and 168 hours (p > 0.05). There was not, however, a statistically significantdifference between Groups D and CC at 24 hours.Conclusion: The latex and non-latex orthodontic separating elastics tested were considered to be biocompatible.(Aust Orthod J 2010; 26: 16–20)

Received for publication: June 2009Accepted: August 2009

Matheus Melo Pithon: [email protected]ério Lacerda dos Santos: [email protected] Otaviano Martins: [email protected] Teresa Villela Romanos: [email protected]ônica Tirre de Souza Araújo: [email protected]

CYTOXICITY OF ORTHODONTIC SEPARATING ELASTICS


Hollywood, CA, USA) (Figure 1). All samples hadrecent manufacturing dates, were from the same pro-duction lot and came in sealed plastic packages.Before testing, the powder coating was removed bywashing the elastics for 15 seconds with deionisedwater in a Milli-Q purification system (Millipore,Bedford, MA, USA). The elastics were then sterilisedby exposure to ultraviolet light (Labconco, Kansas,MO, USA) for 30 minutes.15,16

Volumes of 100 µl L-929 line cells (American TypeCulture Collection – ATCC, Rockville, MD, USA)and growth medium consisting of Eagle’s minimumessential medium (MEM, Cultilab, Campinas,Brazil) plus 0.03 mg/ml of glutamine (Sigma, St.Louis, MO, USA), 50 µg/ml of garamicine (ScheringPlough, Kenilworth, NJ, USA), 2.5 mg/ml of fungi-zone (Bristol-Myers-Squibb, New York, NY, USA),0.25 per cent sodium bicarbonate solution (Merck,Darmstadt, Germany), 10 mmol of HEPES (Sigma,St. Louis, MO, USA) and 10 per cent bovine foetalserum (Cultilab, Campinas, Brazil) were distributedinto 96-well microplates and incubated for 48 hours

at 37 °C. This ensured that the cells adhered to the microplates. After 48 hours, the growth mediumwas replaced with 100 µl of MEM in which the elastics had been incubated for 24, 48, 72 and 168hours.

To verify the cell response in extreme situations, threeadditional groups were included in the study: GroupCC (cell control), consisting of L-929 cells notexposed to supernatants from the elastics; Group C+(positive control), consisting of Tween 80(Polyoxyethylene-20-sorbitan, Sigma, St. Louis, MO,USA); Group C- (negative control), consisting ofphosphate-buffered saline (PBS) solution (Table I).The positive and negative controls were incubated inMEM maintenance medium for 24, 48, 72 and 168hours and the extracted elutes were added to L-929line cells incubated in the growth medium.

Dye uptake The cytotoxicity of the orthodontic elastics was deter-mined with the dye-uptake method, which is basedon the uptake of neutral red by living cells.17 After 24hours incubation, 100 µl of 0.01 per cent neutral reddye (Sigma, St. Louis, MO, USA) was added to eachwell in the microplates and incubated for 3 hours at37 °C. Following this period of time, 100 µl of 4 percent formaldehyde solution (Vetec, Rio de Janeiro,Brazil) in PBS (130 mmol of NaCl; 2 mmol of KCl;6 mmol of Na2HPO4 2H2O; 1 mmol of K2HPO41 mmol; pH 7.2) were added to each well to promotecell attachment to the plate. After 5 minutes, 100 µlof 1 per cent acetic acid (Vetec, Rio de Janeiro, Brazil)and 50 per cent methanol (Vetec, Rio de Janeiro,Brazil) were added in order to remove the dye nottaken up by the cells. After 20 minutes, a spectro-photometer (BioTek, Winooski, VT, USA) set at a

Table I. Experimental and control groups used for the assays.

Groups Trademark/Firm Composition External Reference Batchdiameter number number

(mm)

M Masel Non-latex 4.4 4108-720 132864D Dentaurun Natural latex 4.4 774-200-01 401783A Aditek Natural latex 4.4 159341 081126O OrthoSource Natural latex 4.4 00424-625 205874C+ Tween 80C- PBS solution

Figure 1. Intra-oral separating elastics tested: M (Masel), D (Dentaurum), A(Aditek) and O (OrthoSource).

wavelength of 492 nm was used to determine the dyetaken up by the cells. This test was repeated threetimes and each test used samples of the mediaobtained by incubating 15 new elastics from eachgroup for 24, 48, 72 and 168 hours. Because separat-ing elastics can be in the oral cavity for up to 7 days(168 hours) cell viability was determined after exposure to MEM in which the elastics had beenincubated for 24, 48, 72 and 168 hours.

Data were compared with an analysis of variance(ANOVA) and Tukey’s multiple comparison test wasused to identify statistically significant differencesbetween the groups. The significance level was set atp ≤ 0.05.

Results

There were no statistically significant differencesbetween the viability of the cells in Groups CC, Mand D at 24 hours or between Groups CC and M at48, 72 and 168 hours. Nor were there any statistic-ally significant differences between the viability of thecells in Groups D, A and O at 24, 48 and 72 hours,between Groups M, D and O at 48 hours or GroupsM, D, A and O at 168 hours (Table II). No statistic-ally significant differences were observed betweenGroups M and CC at any experimental time and

between M and D groups at 24, 48 and 168 hours (p > 0.05). There were fewer viable cells in Groups D, A and O at 72 hours compared to the other experimental times (Table II, Figure 2).

At 24 hours the percentage of viable cells variedbetween 97.2 per cent in Group M with the siliconepolymer separator to 92.9 per cent in Group A witha natural rubber latex separating elastic. The percent-age of viable cells fell slightly over the following 24hours in Groups M, A and O, continued to fall inGroups D, A and O between 48 and 72 hours andincreased between 72 and 168 hours.

Discussion

In this cross-sectional study we evaluated the cyto-toxic effects of latex and non-latex separating elasticson cultures of mouse fibroblasts. We used the vitaldye neutral red, which stains viable cells only, andmeasured the optical density of the cells with a spectro-photometer. We determined the percentage of viablecells by comparing the mean optical density of thecells in the control group, which had no contact withthe elastics, with the mean optical densities of thecells in contact with supernatants in which the elastics had been incubated for varying periods oftime. The supernatants from the groups with latex

SANTOS ET AL


Table II. Cell viability at 24, 48, 72 and 168 hours.

Groups N Mean Median SD Cell viability Mean Median SD Cell viability(Per cent) (Per cent)

Time 24 hours Time 48 hours

CC 15 0.680 a 0.710 0.08 100.0 0.720 a 0.735 0.08 100.0C+ 15 0.061 0.078 0.01 9.1 0.059 0.070 0.01 8.3M 15 0.660 a 0.668 0.04 97.2 0.697 ab 0.710 0.052 96.9D 15 0.642 ab 0.658 0.04 94.5 0.681 bc 0.698 0.07 94.6A 15 0.631 b 0.650 0.07 92.9 0.66 c 0.682 0.04 92.6O 15 0.634 b 0.646 0.07 93.3 0.670 bc 0.678 0.08 93.1

Time 72 hours Time 168 hours

CC 15 0.660 a 0.664 0.08 100.0 0.694 a 0.708 0.08 100.0C- 15 0.653 0.710 0.05 99.0 0.682 0.698 0.03 98.4C+ 15 0.060 0.068 0.01 9.1 0.061 0.074 0.01 8.9M 15 0.642 a 0.658 0.08 97.3 0.676 ab 0.690 0.08 97.5D 15 0.608 b 0.622 0.07 92.2 0.659 b 0.666 0.06 95.0A 15 0.594 b 0.604 0.06 90.1 0.645 b 0.658 0.05 93.0O 15 0.605 b 0.616 0.08 91.7 0.653 b 0.670 0.08 94.1

Values followed by same letters are not significantly different (p > 0.05) for the same time.

CYTOXICITY OF ORTHODONTIC SEPARATING ELASTICS


elastics had lower cell viabilities compared to thegroup with silicone polymer separating elastics. Therewas no significant variation in cell viability in the latter group over the experimental period, althoughthe cell viability in all groups increased slightly at 168hours.

The cytoxicity of the supernatants may be due to by-products from the latex elastics or the colourants inthe separating elastics. The latter appears to be anunlikely cause for cell death as Holmes et al.18

reported that the colourants in orthodontic elasticshad low toxicity and could be regarded as ‘clinic-ally inoffensive’. Short-term studies are needed to

investigate further whether colourants affect cell via-bility as they appear to have leached from the surfacelayers of the elastics in the first 24 hours. How-ever, by-products from latex elastics are known to becytotoxic.3,14,19

Spectrophotometric assay is a rapid and reliablemethod of determining cell viability. We used neutralred dye as it is widely used to check L-929 cell viabil-ity. Dead or damaged cells did not take up the vitalstain and were not recognised by the assay.Spectrophotometry does not, however, distinguishdead and damaged cells.

Although L-929 mouse fibroblasts behave similarly toprimary human gingival fibroblasts, the cell cultureresults are only a guide to the human response.12,13

Protocols for direct contact cytotoxicity tests varywidely. Assays using L-929 mouse fibroblasts havebeen shown to give comparable results to cultures ofhuman gingival fibroblasts, and are considered to bean acceptable model for testing the toxicity of sub-stances to gingival fibroblasts in vitro.10–13 There are,however, some limitations to the method: cyotoxicityassays of the same material can give different resultsbecause of differences in production of the cytotoxicsubstance(s) and different cell surface/volumes in theculture medium. Internationally standardised proto-cols are obviously needed to obtain comparableresults and to further develop cytotoxicity screeningtests for the dental materials used in patients.13

Silicone separating elastics were shown to have similar cytotoxicity to the latex separating elastics. Weremoved the powder coating from the elastics before-hand in order to standardise the samples and ensurethat it did not influence the results. We could notdetermine if the powder was cytotoxic or if it con-tributed to the cytotoxicity of the elastics. Accordingto Schmalz,14 potentially cytotoxic intra-oral elastics could release harmful substances that mightaccumulate in the body and over time initiate a disease process. It is known that latex is not entirelybiocompatible and it may interact with certainfoods5,20 and medications.21

The natural latex separating elastics induced more celllysis at 72 hours than at 24, 48 and 168 hours, sug-gesting that toxic substances were ‘released’ after 72hours. These substances could be due to degradationproducts and/or the release of harmful proteins fromthe latex itself. Our finding that the process was not

Figure 2. Percentage viability of tested elastics obtained by spectrophotometry.

continuous is supported by Holmes et al. whoreported that natural latex elastics were biocompat-ible after 3 days intra-oral use.18 As these materials arewidely used in clinical orthodontics and are in inti-mate contact with the gingival tissues, they should beused sparingly or replaced by proven biocompatiblematerials.

The elastics we tested showed over 90 per cent cellviability after 3 days. Other investigators have reported that latex elastics cause more cell death (upto 50 per cent) than non-latex elastics, but concludedthat both types of elastic (latex and non-latex) couldbe used in orthodontics.22 We conclude that the latexand non-latex orthodontic separating elastics we tested have acceptable biocompatibilies, but elasticswith cell viabilities less than 50 per cent should beavoided.14


Dr Mônica Tirre de Souza AraújoUniversidade Federal do Rio de Janeiro - UFRJFaculdade de Odontologia - Departamento deOrtodontiaAv. Prof. Rodolpho Paulo Rocco325 Ilha do FundãoRio de Janeiro – RJ Brasil CEP: 21941-617Email: [email protected]

References 1. Vande Vannet BM, Hanssens JL. Cytotoxicity of two bond-

ing adhesives assessed by three-dimensional cell culture.Angle Orthod 2007;77:716–22.

2. Kao CT, Ding SJ, He H, Chou MY, Huang TH.Cytotoxicity of orthodontic wire corroded in fluoride solution in vitro. Angle Orthod 2007;77:349–54.

3. Fiddler W, Pensabene J, Sphon J, Andrzejewski D.Nitrosamines in rubber bands used for orthodontic pur-poses. Food Chem Toxicol 1992;30:325–6.

4. Hwang CJ, Cha JY. Mechanical and biological comparisonof latex and silicone rubber bands. Am J Orthod DentofacialOrthop 2003;124:379–86.

5. Turjanmaa K, Alenius H, Makinen-Kiljunen S, Reunala T,Palosuo T. Natural rubber latex allergy. Allergy 1996;51:593–602.

6. Tomazic VJ, Withrow TJ, Fisher BR, Dillard SF. Latex-asso-ciated allergies and anaphylactic reactions. Clin ImmunolImmunopathol 1992;64:89–97.

7. Everett FG, Hice TL. Contact stomatitis resulting from theuse of orthodontic rubber elastics: report of case. J Am DentAssoc 1974;88:1030–31.

8. Wakelin SH, White IR. Natural rubber latex allergy. ClinExp Dermatol 1999;24:245–8.

9. Palosuo T, Alenius H, Turjanmaa K. Quantitation of latexallergens. Methods 2002;27:52–8.

10. Schmid-Schwap M, Franz A, Konig F, Bristela M, Lucas T,Piehslinger E et al. Cytotoxicity of four categories of dentalcements. Dent Mater 2009;25:360–8.

11. Franz A, Konig F, Lucas T, Watts DC, Schedle A. Cytotoxiceffects of dental bonding substances as a function of degreeof conversion. Dent Mater 2009;25:232–9.

12. Schedle A, Samorapoompichit P, Rausch-Fan XH, Franz A,Fureder W, Sperr WR et al. Response of L-929 fibroblasts,human gingival fibroblasts, and human tissue mast cells tovarious metal cations. J Dent Res 1995;74:1513–20.

13. Franz A, Konig F, Skolka A, Sperr W, Bauer P, Lucas T et al.Cytotoxicity of resin composites as a function of interfacearea. Dent Mater 2007;23:1438–46.

14. Schmalz G. Use of cell cultures for toxicity testing of dentalmaterials – advantages and limitations. J Dent 1994;22Suppl 2:S6–11.

15. Santos RL, Pithon MM, Oliveira MV, Mendes GS, RomanosMT, Ruellas AC. Cytotoxicity of intraoral orthodontic elastics. Braz J Oral Sci. 2008;7:1520–5.

16. Santos RL, Pithon MM, Mendes GS, Romanos MT, RuellasAC. Cytotoxicity of intermaxillary orthodontic elastics ofdifferent colors: An in vitro study. J Appl Oral Sci 2009;17:326–9.

17. Neyndorff HC, Bartel DL, Tufaro F, Levy JG. Developmentof a model to demonstrate photosensitizer-mediated viralinactivation in blood. Transfusion 1990;30:485–90.

18. Holmes J, Barker MK, Walley EK, Tuncay OC. Cytotoxicityof orthodontic elastics. Am J Orthod Dentofacial Orthop1993;104:188–91.

19. Perrella FW, Gaspari AA. Natural rubber latex proteinreduction with an emphasis on enzyme treatment. Methods2002;27:77–86.

20. Carey AB, Cornish K, Schrank P, Ward B, Simon R. Cross-reactivity of alternate plant sources of latex in subjects withsystemic IgE-mediated sensitivity to Hevea brasiliensis latex.Ann Allergy Asthma Immunol 1995;74:317–20.

21. Towse A, O’Brien M, Twarog FJ, Braimon J, Moses AC.Local reaction secondary to insulin injection. A potentialrole for latex antigens in insulin vials and syringes. DiabetesCare 1995;18:1195–7.

22. Hanson M, Lobner D. In vitro neuronal cytotoxicity of latexand nonlatex orthodontic elastics. Am J Orthod DentofacialOrthop 2004;126:65–70.

SANTOS ET AL


Introduction

Although self-ligating (SL) brackets have been avail-able for many years they have recently become popular with clinicians because of claims that theyresult in shorter treatment times. There is some evi-dence that these brackets can be ligated quickly andhave less friction than conventional brackets.1–3

Many of these claims have been based on evidencefrom retrospective clinical studies, which may be con-founded by factors such as the proficiency of the clinician(s), the treatment mechanics used and/orobserver bias.4,5 Randomised clinical trials attempt toovercome the shortcomings of retrospective trials, butthey may have limitations also, such as the use ofarchwires with different dimensions.6 Prospectiveclinical trials that have used identical wire sequencesfound no difference in the ability to align anterior teethbetween SL brackets and conventional brackets.7–13

There is little doubt that the latches on SL bracketscan be unfastened and closed more quickly than elasto-meric modules or wire ligatures can be removed andplaced on conventional brackets. Time savings of upto 10–12 minutes per patient for SL brackets com-pared with tying steel ligatures and 2–3 minutes compared with elastomeric modules have beenreported.1,5,14,15 Many patients would like their treat-ment to be as short and as inconspicuous as possible,and for these reasons they prefer to have porcelain orplastic brackets bonded on their upper anterior teeth.

The aims of this study are to compare the effective-ness of SL porcelain brackets with conventional porce-lain (CP) brackets tied with ligatures for initial alignment in the upper arch, to compare the discomfortof both bracket – archwire combinations and to com-pare the times taken (both assisted and unassisted) tountie and ligate both bracket – archwire combinations.


Porcelain brackets during initial alignment: areself-ligating cosmetic brackets more efficient?

Peter Miles* and Robert Weyant†

Private practice, Caloundra, Queensland, Australia* and the Division of Pediatric and Developmental Dental Sciences, School of DentalMedicine, University of Pittsburgh, Pittsburgh, U.S.A.†

Objective: To compare the effectiveness of a self-ligating (SL) porcelain bracket with a conventional porcelain (CP) bracket tiedwith ligatures for initial alignment in the upper arch, to compare the discomfort of both bracket – archwire combinations and tocompare the times taken (both assisted and unassisted) to untie and ligate both bracket – archwire combinations.Methods: Sixty nonextraction patients were randomly assigned to either a group with CP brackets on the upper six anteriorteeth and conventional metal brackets on the premolars and first molars, or a group with SL porcelain brackets on the anteriorteeth and SL metal brackets on the posterior teeth. The CP brackets were tied with coated ligatures. The irregularity index wasmeasured at the start of treatment and at the first recall 10.7 weeks later. Discomfort was recorded over the first week with aLikert scale and the times to untie and ligate the six anterior porcelain brackets (assisted and unassisted) were recorded.Results: There were no differences in irregularities at the start of treatment (p = 0.91) or 10.7 weeks later (p = 0.12). No sig-nificant difference in discomfort was found between the bracket types (p = 0.90). The porcelain SL brackets were significantlyfaster (p < 0.001) to untie and ligate than the CP brackets with ligatures.Conclusion: Porcelain SL brackets were faster to untie and ligate by 22 seconds per bracket, but there were no significant differences in the alignment achieved or discomfort experienced.(Aust Orthod J 2010; 26: 21–26)

Received for publication: September 2009Accepted: October 2009

Peter Miles: [email protected] Weyant: [email protected]

MILES AND WEYANT


Subjects and methods

Sixty-eight consecutive subjects, scheduled for non-extraction treatment in the upper arch, were drawnfrom the senior author’s private orthodontic practice.All subjects agreed to participate in the study after thepurpose had been explained to them. The subjectswere not informed which bracket was the newerdesign.

The subjects were randomly allocated to one of twogroups. In Group 1, SL porcelain 0.018 inch In-Ovation C brackets (GAC International, Bohemia,NY, USA) were indirectly bonded to the upper incisors and canines and metal In-Ovation bracketswere indirectly bonded on the upper premolars andfirst molars. In Group 2, conventional porcelain (CP)0.018 inch Clarity brackets (3M/Unitek, Monrovia,CA, USA) were bonded indirectly to the upper incisors and canines and Victory brackets (3M/Unitek, Monrovia, CA, USA) were bonded to theupper premolars and first molars.

Of the 68 patients enrolled in the study, follow-upimpressions were missed for two subjects in Group 1and four subjects in Group 2 (Figure 1). Two sub-jects, matched for age, gender and incisor irregularitywith two subjects in Group 2, were dropped fromGroup 1 to keep the same number of subjects in eachgroup. At analysis both groups had 19 female subjectsand 11 male subjects. The overall mean age at theconclusion of the trial was 13.5 + 1.5 years.

Alginate impressions for study models were takenprior to bonding. Immediately after bonding a 0.014inch G4 heat-activated NiTi wire (G & H WireCompany, Franklin, IN, USA) was placed in eachsubject. To prevent the archwire from sliding aroundthe arch and interfering with the incisors duringalignment, V-bends were placed distal to each centralincisor. The six anterior CP brackets were ligated withcoated ligatures while elastomeric modules (3MUnitek, Monrovia, CA, USA) were used on the pre-molars. The SL In-Ovation brackets were ‘ligated’using the clip mechanism in the bracket. The first

Randomised(N = 68)

Group 1Allocated to In-Ovation C (N = 34)

Received allocated intervention (N = 34)

Group 2Allocated to Clarity (N = 34)

Received allocated intervention (N = 34)

Lost to follow-up (N = 0)Impression missed (N = 4)

Analysed (N = 30)Excluded from analysis (N = 0)

Lost to follow-up (N = 0)Impression missed (N = 2)

Analysed (N = 30)Excluded from analysis (N = 2)

Enr

olm

ent

Allo

catio

nFo

llow

-up

Ana

lysi

s

Figure 1. Flow chart showing the progress of patients through the trial.

wire change was scheduled approximately 10 weeksafter bonding, at which time a second alginateimpression and photographs were taken of the upper arch.

The alginate impressions were poured up in dentalstone for later measurement of the irregularityindex.16 The irregularity index, defined as the summeddisplacement of adjacent anatomical contact pointsof the six anterior teeth, was measured using a digitalcaliper to the nearest 0.1 mm with the operator blinded to the identity of each cast.

The irregularity data before the start of the trial (T1)and after approximately 10 weeks (T2) were com-pared with a one-way analysis of variance (ANOVA).The irregularity data were also divided into two sub-groups: subjects with an initial irregularity score < 5.0mm and subjects with an initial irregularity score ≥ 5.0 mm.6

To assess the accuracy of measuring the irregularityindex, 10 models were randomly selected and remeasured one month after the first set of measure-ments. Pearson’s correlation coefficient and a paired t-test were used to assess the accuracy and repro-ducibility of the method. There was no significantdifference between the two sets of measurements(Mean difference: 0.06 mm, p = 0.76, r = .98) indicating that the irregularity measurements werereliable.

To assess the discomfort with each type of bracket,the subjects were asked to record the levels of dis-comfort in the upper arch on a 7-point Likert scale 4 hours, 24 hours, 3 days and 1 week after placementof the initial archwire. They were also asked to returnthe questionnaires at the following visit. The 4-, 24-hour, 3-day and 1-week and total discomfort scoreswere compared with a one-way ANOVA and withpost-hoc Tukey’s HSD test for multiple comparisons.

The times taken by the senior author to untie and ligate 10 consecutive cases from each group, and the

times taken by the senior author assisted by a staffmember to untie and ligate the CP brackets in 10consecutive subjects were compared with a one-wayANOVA.

ResultsThere were no statistically significant differencesbetween the irregularity scores in the groups eitherpretreatment (T1) or 10.7 weeks later (T2). At T2 the anterior teeth in the self-ligating group wereslightly less irregular than the anterior teeth in theClarity group, but the difference was not statisticallysignificant (Table I).

When the irregularity data were subdivided into thelow irregularity (< 5 mm) and high irregularity (≥ 5 mm) subgroups, there were no statistically significant group differences at T1 (Low irregularitysubgroup: SL vs CP, p = 0.92; High irregularity sub-group: SL vs CP, p = 0.63) or T2 (Low irregularitysubgroup: SL vs CP, p = 0.95; High irregularity sub-group: SL vs CP, p = 0.11).

Of the 60 patients who completed the study, 42 (70per cent) returned the discomfort questionnaires. Todetermine if there was any difference in the irregular-ity scores of those who returned the questionnaires

ARE SELF-LIGATING COSMETIC BRACKETS MORE EFFICIENT?


Table I. Irregularity scores for each bracket type, in millimetres.

Time In-Ovation C Clarity pMean (SD) Mean (SD)

T1 7.0 (3.4) 7.1 (3.0) 0.91T2 2.3 (1.0) 2.7 (1.1) 0.12

T1, pretreatment; T2, recall at approximately 10.7 weeks

Table III. Times taken to untie and ligate six porcelain brackets unassist-ed and assisted by a staff member, in seconds.

In-Ovation C Clarity ClarityMean (SD) Assisted Unassisted

Untying 9.2 (2.5) a,b 31.5 (10.2) a 32.2 (12.9) bLigating 12.4 (6.3) a,b 91.2 (5.8) a,c 119.6 (8.7) b,cTotal 21.6 (7.5) a,b 122.7 (10.1) a,c 151.8 (16.3) b,c

The letters indicate groups significantly different at p < 0.001 withTukey’s HSD test.

Table II. Ratings of upper arch discomfort for each bracket type.

Time In-Ovation C Clarity pMean rating (SD) Mean rating (SD)

4-hours 2.8 (1.5) 2.4 (1.1) 0.421-day 3.4 (1.8) 3.9 (1.7) 0.333-days 2.5 (1.5) 2.4 (0.9) 0.877-days 1.6 (1.1) 1.3 (0.6) 0.29Total 10.2 (5.2) 10.1 (3.2) 0.90

MILES AND WEYANT


and those who did not, the T2 irregularity scores ofthese two subgroups were compared. There were nostatistically significant differences between the irregul-arity scores of the SL subjects either with or withoutpain scores (p = 0.85) or for the CP subjects with orwithout pain scores (p = 0.19). There were no statis-tically significant group differences in the subjects’ratings of discomfort at any of the time intervals or inthe total rating (Table II).

The times to untie and ligate the six anterior SLbrackets unassisted and the six anterior CP bracketsunassisted and assisted, are given in Table III. The SLbrackets could be untied and ligated significantlyfaster than the CP brackets either assisted or unassisted(p < 0.001). On average, the SL brackets could beuntied and ligated 1 minute 41 seconds (assisted) or2 minutes 10 seconds (unassisted) less than the CPbrackets. The help of an assistant saved no time whenuntying the CP bracket (p = 0.89), but tying ligatureswith the help of an assistant saved 29 seconds for thesix CP brackets (p < 0.001).

Discussion

We found that SL and CP brackets with 0.014 inchNiTi archwires were equally effective at aligning theupper six anterior teeth and that our subjects consid-ered both bracket – archwire combinations equallyuncomfortable. We did, however, find significant savings in the times required to untie and ligate theSL brackets over the CP brackets, which is hardly sur-prising as the SL brackets were closed with a latch,whereas the CP brackets were ligated with coated lig-atures. An assistant significantly reduced the timerequired to ligate the CP brackets.

Coated ligatures were used on the CP brackets as elastomeric modules could not be tied in a figure-8on these ceramic brackets. The ligatures ensured thatthe archwire was seated in the bracket slots. Small,but statistically significant, improvements in align-ment have been reported for conventional metalbrackets tied with either modules in a figure-8 patternor steel ligatures over passive SL brackets.7,8 On theother hand, no statistically significant differences inlower arch alignment were found between SL bracketsand metal conventional brackets,9–11 or betweenactive and passive SL brackets in upper arch aligment.17

In addition to the method of ligation, factors such astooth shape, slot dimensions, bracket width andbracket position may influence alignment. We

limited the variation due to bracket position by using an indirect bonding technique and randomlyassigning the subjects to both groups.

As we found no difference in alignment, the smalldifferences reported in previous studies could be due to the use of a passive rather than an active SLbracket. The bracket geometry may also be a factor assome SL brackets are narrower than conventionalbrackets and offer less rotational control. A recentstudy comparing an active SL bracket with a passiveSL bracket in the upper arch found no significant dif-ference in the time required to attain alignment,17

and a study comparing plastic/metal Damon 3 SLbrackets with conventional metal brackets ligatedwith elastomeric modules also found no differenceduring initial alignment in the lower arch.9

In agreement with previous studies we found no sig-nificant difference in the ratings of discomfortbetween the different brackets.18–20 In other words,the SL bracket – archwire combination was no moreuncomfortable during initial alignment than the CPbracket – archwire combination. On four out of fiveoccasions the Clarity group ratings were slightly less,but not significantly so, than the ratings by the In-Ovation C group. The lack of significant findingscould also be due to the lack of sensitivity of theLikert rating scale, because the raters had differentframes of reference or because they were influencedby what they thought was the purpose of the scale.The Likert scale was used in this study to enable ourresults to be compared with other studies using thesame method.

A previous study reported that SL brackets were nomore efficient in terms of the time required to alignincisors with high irregularity scores (≥ 5 mm) thanconventional brackets, but incisors with low irregul-arity scores (< 5 mm) were aligned more quickly withSL brackets.6 In that study two different wiresequences were used for each bracket type: the secondarchwire in the conventional bracket group was around wire whereas a rectangular archwire was usedin the SL bracket group. Use of archwires with differ-ent cross-sections may have accounted for the differ-ent results. We used identical archwires in bothgroups and found no significant difference betweenthe subjects with low irregularity scores (< 5 mm) andthose with high scores (≥ 5 mm).

Anecdotal reports have suggested that high caninesrespond more favourably to the lesser friction of SL

brackets. We subjectively assessed the subjects in ourstudy and found four with high canines: two subjectsin each group. The mean irregularities reduced from12.0 mm to 1.8 mm in the subjects with CP bracketsand from 11.4 mm to 1.2 mm in the subjects with SLbrackets (Figure 2). In both cases the mean improve-ment in alignment was identical at 10.2 mm. This isnot unexpected as displacement of the archwire intothe bracket on a high canine can result in the arch-wire binding and notching, which are the major contributors to resistance to sliding.

In the present study, untying and ligating SL bracketson the upper anterior teeth saved a small, but statisti-cally significant, amount of time over the timerequired to untie and ligate the CP brackets. Withouthelp from an assistant the time saved with six anter-ior SL brackets averaged 2 minutes 10 seconds or 22seconds per bracket compared with a ligature tie oneach CP bracket. Extrapolating this time saving to 20SL brackets in both arches could save approximately7 minutes 20 seconds over CP brackets tied with ligatures. This time saving is less than the saving of 10–12 minutes reported by others when using ligatures.14 Although the time savings were small, apotential saving of 2 minutes 10 seconds at each visit

could add up to approximately 32 minutes over thecourse of 15 visits if ligatures were replaced at everyvisit.

During initial alignment it is important to engage thewire completely to gain the maximal correction ofrotations and vertical alignment. Once alignment hasbeen achieved, elastomeric modules, which can beplaced more quickly, can be used to maintain the cor-rection and time savings would be less. The time savings of SL brackets compared with modules are inthe order of one minute for both arches.5,15 This rep-resents only a portion of the actual chair time duringan orthodontic adjustment and, depending upon theutilisation of staff and flow of patients in the office,may have little impact upon practice efficiency. Insome circumstances small gains in efficiency may bepossible if the orthodontist works unaided. However,if an auxiliary ligates the archwire and the orthodon-tist is not available to check the patient, efficiency willdepend upon the availability of the orthodontistrather than the method of ligation. In some cases,such as using chain or a long ligature to close or con-solidate space closure or prevent spaces opening, having to close a clip or gate on an SL bracket as wellas tying a chain or ligature could actually add a small

ARE SELF-LIGATING COSMETIC BRACKETS MORE EFFICIENT?


Figure 2. Subjects with high canines. Both subjects had 0.014 inch heat-activated NiTi archwires.Top left, Group 1 subject at T1; Top centre, the same Group 1 subject at T1; Top right, the same Group 1 subject at T2 (CP and metal brackets).Bottom left, Group 2 subject at T1; Bottom centre, the same Group 2 subject at T1; Bottom right, the same Group 2 subject at T2 (SL porcelain and SL metal brackets).

amount of time compared with a conventional bracket. Finally, the bracket and ligation mechanismneed to be reliable throughout the course of treat-ment. If a clip or gate ‘locks’ and cannot be opened,or distorts or breaks during treatment, then this canaffect either the time to ligate the bracket and/or theability of the bracket to align the tooth if the bracketis not fully engaging the archwire. Future researchwill need to evaluate the full-course of treatment withdetailed records of any difficulties. This is highlight-ed by a previous retrospective study that found nodifference between an active SL bracket and a con-ventional bracket in overall treatment time or number of visits, but reported significantly morebreakages and emergencies using the SL bracket.12

Conclusions

There were no significant differences between self-ligating porcelain brackets and conventional por-celain brackets in aligning the upper anterior teeth orthe discomfort experienced by the subjects.

Self-ligating porcelain brackets were significantlyfaster to untie and ligate than the conventional porcelain brackets tied with coated ligatures.


Dr Peter Miles10 Mayes AvenueCaloundra Qld 4551AustraliaEmail: [email protected]

References1. Shivapuja PK, Berger J. A comparative study of convention-

al ligation and self-ligation bracket systems. Am J OrthodDentofac Orthop 1994;106:472–80.

2. Sims AP, Waters NE, Birnie DJ, Pethybridge RJ. A compar-ison of the forces required to produce tooth movement invitro using two self-ligating brackets and a pre-adjustedbracket employing two types of ligation. Eur J Orthod 1993;15:377–85.

3. Pizzoni L, Ravnholt G, Melsen B. Frictional forces related toself-ligating brackets. Eur J Orthod 1998;20:283–91.

4. Eberting JJ, Straja SR, Tuncay OC. Treatment time, out-come, and patient satisfaction comparisons of Damon andconventional brackets. Clin Orthod Res 2001;4:228–34.

5. Harradine NW. Self-ligating brackets and treatment efficiency. Clin Orthod Res 2001;4:220–7.

6. Pandis N, Polychronopoulou A, Eliades T. Self-ligating vsconventional brackets in the treatment of mandibularcrowding: a prospective clinical trial of treatment durationand dental effects. Am J Orthod Dentofacial Orthop 2007;132:208–15.

7. Miles PG. Smartclip versus conventional twin brackets forinitial alignment: is there a difference? Aust Orthod J2005;21: 123–7.

8. Miles PG, Weyant RJ, Rustveld L. A clinical trial of Damon2 versus conventional twin brackets during initial alignment. Angle Orthod 2006;6:480–5.

9. Scott P, DiBiase AT, Sherriff M, Cobourne MT. Alignmentefficiency of Damon 3 self-ligating and conventional ortho-dontic bracket systems: a randomized clinical trial. Am JOrthod Dentofacial Orthop 2008;134:470.e1–8.

10. Fleming PS, DiBiase AT, Lee RT. Randomised controlledtrial of mandibular alignment with two pre-adjusted appliances. J Orthod 2008;35:223–4 (Abstract).

11. O’Dwyer LA, Littlewood SJ, Rahman S, Spencer RJ.Efficiency of SmartClip self-ligating brackets compared tobrackets using conventional ligation. J Orthod 2008;35:226(Abstract).

12. Hamilton R, Goonewardene MS, Murray K. Comparison ofactive self-ligating brackets and conventional pre-adjustedbrackets. Aust Orthod J 2008;24:102–9.

13. Justine Brock. A comparison of initial alignment and painwith self-ligating and conventionally ligated bracket systems.University of Queensland, Thesis submitted in partial fulfil-ment of the requirements for the Degree of Doctor ofClinical Dentistry (Orthodontics), 2008.

14. Berger J, Byloff FK. The clinical efficiency of self-ligatedbrackets. J Clin Orthod 2001;35:304–8.

15. Turnbull NR, Birnie DJ. Treatment efficiency of conven-tional vs self-ligating brackets: effects of archwire size andmaterial. Am J Orthod Dentofacial Orthop 2007;131:395–9.

16. Little R. The Irregularity Index: a quantitative score ofmandibular anterior alignment. Am J Orthod 1975;68:554–63.

17. Pandis N, Polychronopoulou A, Eliades T. Active or passiveself-ligating brackets? A randomized control trial of compar-ative efficiency in resolving maxillary anterior crowding inadolescents. Am J Orthod Dentofacial Orthop 2009;Accepted for publication.

18. Scott P, Sherriff M, DiBiase AT, Cobourne MT. Perceptionof discomfort during initial orthodontic tooth alignmentusing a self-ligating or conventional bracket system: a ran-domized clinical trial. Eur J Orth 2008;30:227–32.

19. Rahman S, Spencer RJ, O’Dwyer LA, Littlewood SJ.SmartClip versus a conventional pre-adjusted edgewiseappliance – Is there a difference in pain and breakages? JOrthod 2008;35:226–7 (Abstract).

20. Fleming PS, DiBiase AT, Sarri G, Lee RT. Pain experienceduring initial alignment with a self-ligating and a conven-tional fixed orthodontic appliance system: a randomizedcontrolled clinical trial. Angle Orthod 2009;79:46–50.

MILES AND WEYANT


Introduction

Facial appearance is an important factor in many cul-tures and the mouth and teeth in particular are majorfactors determining our perceptions of emotion andfacial attractiveness.1–3 In orthodontics, we generallyevaluate dentofacial attractiveness from a lateral viewrather than in a full or three-quarter view of theface.4–8 The latter two views are widely used by the media to illustrate and identify faces while theprofile view is generally reserved for postage stamps,coins and orthodontic publications. It could beargued that an assessment of facial aesthetics shouldbegin by viewing the patient from the front, at rest,

during conversation and smiling.8 The extent to whichthe anterior teeth are displayed when the lips are atrest and during activities, such as smiling, may influ-ence our perception of facial attractiveness and shouldbe part of the initial orthodontic assessment.3,7

Various authors have described a gradual reduction inthe display of the upper central incisors and anincrease in lower incisor display with increasingage.9–12 The display of lower incisors in individuals60 years or older was reported to be similar to the dis-play of upper incisors in subjects less than 30 years ofage.9 Furthermore, women tend to show more oftheir upper anterior teeth and less of their lower


Display of the incisors as functions of age and gender

Andrea Fonseca Jardim da Motta,* Margareth Maria Gomes de Souza,* Ana MariaBolognese,* Clarice Júlia Guerra† and José Nelson Mucha†

Department of Orthodontics, School of Dentistry, Federal University of Rio de Janeiro* and the Department of Clinical Dentistry, School ofDentistry, Fluminense Federal University,† Rio de Janeiro, Brazil

Background: Older subjects usually show less of their upper incisors and more of their lower incisors than younger subjects.Objectives: To determine how much of the upper and lower central incisor crowns are visible in Brazilian subjects with their lipsat rest.Methods: The subjects were 240 white Brazilian subjects divided into four age groups: Group 1, 12 to 15 years of age;Group 2, 20 to 30 years of age; Group 3, 31 to 50 years of age and Group 4, 51 years of age and older. Each groupcontained 30 males and 30 females. The vertical display of the incisors was measured in millimetres from the midpoints of theincisal edges of the upper and lower central incisors to the borders of the upper and lower lips.Results: In females, the mean upper central incisor display reduced from 4.45 mm in Group 1 to 1.32 mm in Group 4, and inmales it reduced from 3.35 mm in Group 1 to 0.57 mm in Group 4. Less of the lower central incisor crowns were displayedin Group 1 females (Mean: 0.47 mm) than in Group 4 females (Mean: 2.22 mm), and in Group 1 males (Mean: 0.61 mm)than in Group 4 males (Mean: 3.05 mm). Brazilian women showed significantly more of their upper incisor crowns thanBrazilian men in Groups 1, 2 and 4, whereas Brazilian men showed significantly more of their lower central incisors thanBrazilian women in Group 4.Conclusions: With the lips at rest, older Brazilians display less of their upper central incisors and more of their lower centralincisors than young Brazilians. Women show more of their upper incisors than men, while men display more of their lower central incisors than women.(Aust Orthod J 2010; 26: 27–32)

Received for publication: June 2009Accepted: November 2009

Andrea Fonseca Jardim da Motta: [email protected] Maria Gomes de Souza: [email protected] Maria Bolognese: [email protected] Júlia Guerra: [email protected]é Nelson Mucha: [email protected]

MOTTA ET AL


anterior teeth than men.9,11–13 However, Peck et al.found no significant gender differences in the rela-tionships between the upper lip and the teeth withthe lips at rest.10

Although various authors have suggested guidelinesfor the arrangement of the anterior teeth, no authorhas reported the extent to which the anterior teeth arevisible in the frontal view in a mixed population,when the lips are relaxed.9,10,12,15 We aim to deter-mine how much of the upper and lower central incisor crowns are visible in the white Brazilian sub-jects with their lips at rest, and to determine if ageand gender influence the findings.

Materials and methodsThe subjects in this cross-sectional study were 120male and 120 female white Brazilians between 12 and72 years of age. The subjects were divided into thefollowing age groups: 12 to 15 years of age (Group 1);20 to 30 years of age (Group 2); 31 to 50 years of age(Group 3); 51 years of age and older (Group 4). Eachgroup consisted of 30 males and 30 females ran-domly selected from three sources. The subjects inGroup 1 were selected from students attending a cityhigh school and the subjects in Group 2 were select-ed from dental students attending the FederalUniversity of Rio de Janeiro. Group 3 and 4 subjectswere selected from patients attending two privatedental clinics. The subjects in all groups were ran-domly selected from those that met the inclusion cri-teria using the Statistical Package for the SocialSciences (SPSS Inc., Chicago, IL, USA).

At the time of examination all subjects lived in Rio deJaneiro. According to the latest National Survey of

Households, conducted by the Brazilian Institute ofGeography and Statistics (IBGE), white Braziliansmake up 53.6 per cent of the metropolitan popula-tion. The remainder are: Pardos, a mixture of Whites,Blacks and Indigenous groups with complexionsvarying from light to dark (33.6 per cent); blackBrazilians (12.3 per cent); Asian and/or IndigenousBrazilians (0.5 per cent).

Only white Brazilians with orthognathic profiles, nofacial disharmony, normal occlusion or Angle Class Imalocclusion who would not benefit from any formof orthodontic treatment were included. Subjectswith a history of facial surgery, anterior dental trauma, restored upper or lower incisors or previousorthodontic treatment were excluded.

Measurements of incisor display were obtained withthe lips at rest and mandibular posture unstrained.10,16

The following procedure was used: subjects wereasked to stand in front of the examiner in a naturalupright posture with Frankfort plane parallel to thefloor.16 They were then instructed to wet their lipswith their tongues, open their mouths gently, swallowand articulate the word ‘Emma’.17 Each subject’s pos-ture was checked twice to ensure that the lips were atrest and the teeth slightly apart.8

The amounts of upper and lower central incisorcrowns displayed were then measured with a dialcaliper from the midpoints of the incisal edges ofboth upper central incisors to the lower border of theupper lip and from the midpoints of both lower central incisors to the upper border of the lower lip(Figure 1).9,12 When measurements of the right andleft central incisors differed, the mean of both incisorswas used, and when an incisor could not be seen themeasurement was considered to be zero.

The entire procedure was performed by a singleexaminer and the error of the method was establishedby repeating the measurements in 60 subjects, oneweek apart. In order to verify the intra-examiner systematic error, Student’s paired t-tests were appliedand the random error was calculated using Dahlberg’sformula.18 The results of the error analysis indicatedthat the method was reliable because the differenceswere not statistically significant and Dahlberg’s for-mula revealed that the errors ranged from 0.22 to0.31 mm.

The Kruskal-Wallis non-parametric test was per-formed to assess differences between the age groups

Figure 1. Measurement of upper central incisor display.

and genders, and when a significant difference wasfound the Mann-Whitney U test was used. Probabil-ities < 0.05 were considered to be statistically significant.

Results

The results indicate that the display of the upper incisors declined with age in both genders, and thatmale Brazilians showed less of their upper incisorsthan female Brazilians (Table I). In both gendersthere was a gradual increase in lower incisor displaywith age.

In the youngest female subjects (Group 1) 4.45 ±1.19 mm of the upper incisor crowns were visiblebelow the upper lip and in the youngest male subjects3.35 ± 1.14 mm of the upper incisor crowns were vis-ible. The lengths of the upper central incisors crownsvisible below the upper lips in the females fell steadilywith increasing age from 3.37 ± 1.28 mm (Group 2),to 2.25 ± 0.87 mm (Group 3) to 1.32 ± 1.18 mm(Group 4). The lengths of the upper incisors crownsvisible below the upper lips in the males fell at a similar rate from 3.35 ± 1.14 mm in Group 1 to 0.57± 0.53 mm in Group 4 (Figure 2).

In the female subjects, the lengths of lower centralincisors displayed at rest increased from a mean of 0.47 mm in Group 1, to 0.60 mm in Group 2,

1.75 mm in Group 3 and 2.22 mm in Group 4. Theincrease was greater in the male subjects than in thefemale subjects: 0.61 mm in Group 1, 0.97 mm inGroup 2, 1.82 mm in Group 3 and 3.05 mm inGroup 4 (Figure 3).

Table II gives gender comparisons of the upper andlower incisor display for the different age groups. Inall age groups, the female subjects displayed more ofthe upper central incisors than the male subjects, andthe males showed more of their lower incisor crownsthan the female subjects. The male – female differ-ences for upper incisor display reached statistical sig-nificance in Groups 1, 2 and 4 and for lower incisordisplay in Group 4 (Table II).

Comparisons of incisor display in the various groupsand for both genders are given in Table III. In thefemale subjects, the decrease in upper incisor displaywas significant when all groups were compared witheach other, but there were no significant differencesin lower incisor display in Groups 1 and 2, andGroups 3 and 4. In males, the display of upper inci-sors fell significantly in all groups, except betweenGroups 2 and 3. The age-related increase in the dis-play of lower incisors in the men was not significantwhen comparing Groups 1 and 2, but it was signifi-cant for the other groups.

DISPLAY OF INCISORS AS FUNCTIONS OF AGE AND GENDER


Table I. Upper and lower central incisor display with the lips at rest.

Group Central Gender Mean SD Median Minimum Maximumincisors (mm) (mm)

Group 1 (12–15 years) Upper Female 4.45 1.19 4.62 2.49 6.39Male 3.35 1.14 3.35 1.09 5.57

Lower Female 0.47 0.42 0.50 0.00 1.06Male 0.61 0.57 0.66 0.00 1.72





Group 4 (≥ 51 years) Upper Female 1.32 1.18 1.24 0.00 3.55Male 0.57 0.53 0.60 0.00 1.94


MOTTA ET AL


Discussion

We measured the upper and lower incisor crowns vis-ible below and above the margins of the lips in whiteBrazilians living in Rio de Janeiro. When the lips wereat rest, we found the upper incisor display reducedwith age and the lower incisor display increased inwomen and men. As a rule, the women showed moreof their upper incisors than the men, while the mendisplayed more of their lower incisors than thewomen. These findings may have important implica-tions for orthodontic treatment planning, whichtends to ignore long-term changes in the incisor – liprelationships.

One aspect that must be considered is that the sample selected for this study may not be representa-tive of all white Brazilians since the research was held in the city of Rio de Janeiro and Brazil is a large

country with five geographical regions and severallarge cities. As can be seen from the data provided bythe IBGE (the agency responsible for statistical, geo-graphic, cartographic, geodetic and environmentalinformation in Brazil) the country’s population isdiverse, comprising many races and ethnic groups. Soit is possible that white Brazilians from SouthernBrazil may differ from white Brazilians in the Northof the country. However, the results obtained in thisstudy confirm what others have reported on upperand lower incisor display.

The display of the anterior teeth is relevant not onlyfor dental aesthetics, but also for facial attractiveness.The shape, alignment, position and display of the upper central incisors determine a pleasant smile and should be considered when planningorthodontic treatment.20 One of the challenges anorthodontist or restorative dentist may face is to determine the extent to which damaged upperincisors should be displayed. In such situations, therelationship between the upper lip and the displayedportion of the anterior teeth at rest is an importantconsideration.5–8,10,12,21

We selected subjects with a normal or Angle’s Class Imalocclusion. Subjects with the latter condition hadslightly misaligned teeth, but it was not severeenough to require orthodontic treatment. Althoughthe subjects we selected may not be representative ofthe patients seeking orthodontic treatment, our average values can be used as reference points orguidelines for incisor display, particularly for smileaesthetics in the long-term.

Figure 2. Mean values (mm) for the display of upper incisors, by age andgender.

Figure 3. Mean values (mm) for the display of lower incisors, by age andgender.

Table II. Gender comparisons of upper and lower incisor display.

Group Central Median (mm) U* pincisors Females Males

Group 1 Upper 4.62 3.35 235.0 < 0.01(12–15 years) Lower 0.50 0.66 363.5 > 0.05Group 2 Upper 3.64 1.89 205.0 < 0.0120–30 years) Lower 0.50 0.58 372.5 > 0.05Group 3 Upper 2.49 1.53 334.0 > 0.05(31–50 years) Lower 1.56 1.52 426.0 > 0.05Group 4 Upper 1.24 0.60 282.5 < 0.05(≥ 51 years) Lower 2.24 3.12 312.5 < 0.05

* Mann-Whitney U test, significant values in bold

4.54

3.53

2.52

1.51

0.50

Group 1 Group 2 Group 3 Group 412 to 15 20 to 30 31 to 50 50 years

years years 50 years or more

FemaleMale

mm

3.5

3

2.5

2

1.5

1

0.5

0Group 1 Group 2 Group 3 Group 412 to 15 20 to 30 31 to 50 50 years

years years 50 years or more

FemaleMale

mm

0.57

1.321.73

2.252.24

3.573.45

4.45

1.821.75

2.22

3.05

0.970.60.61

0.47

Some authors consider that the smile is the main aes-thetic factor in an orthodontic diagnosis.12–24 Usefulinformation can be obtained by observing a patientduring normal conversation, but care should be exer-cised when observing the upper lip as it moves from the rest position to a full smile as the final position can be highly variable.8 The positions of the incisal edges of the upper incisors relative to therelaxed lips are often used in orthodontic treat-ment planning as a vertical reference point. Thedetermination of the ‘relaxed lips position’ is repro-ducible, but not easily obtained for all patients or onsome occasions.21

Our findings on the age changes in the display of the upper and lower incisors and, in particular, thereduced display of the upper anterior teeth andincreased display of lower anterior teeth with age,agree with previous studies.9–12 These results confirmprevious reports that young people display more oftheir upper incisors than older people.5,14 Thesechanges were not determined by changes in the posi-tions of the teeth, but rather by age-related changes inthe facial tissues and the effect of gravity on the lips.25

Elongation of the lips continues throughout life andexceeds the age-related increase in lower anterior faceheight.19 The positions of the lips also depend on factors such as lip length, lip type and muscle tonus,but we did not assess these factors.

Age-related changes in incisor display can be under-estimated if the sample includes subjects from a narrow age band.10 We used subjects between 12 and72 years, but only the gender comparisons between

Groups 1, 2 and 4 were statistically different. It isimportant that incisor display is appropriate for theage of the patient. The prosthodontic literature typically recommends that artificial teeth are set up sothat 2 mm of the central incisor crowns are visiblewhen the lips are at rest, but patients who want amore youthful appearance will often ask for more oftheir incisor crowns to be visible.14 When the displayof the anterior teeth is considered insufficient (e.g.excessive tooth wear) the patient’s age can be used asa reference to determine the average length of incisorsvisible at rest. In orthodontic treatment planning themean values can be used to establish the amount ofintrusion to be performed in the upper and/or lowerarches. Over-intrusion of the upper incisors in youngpatients may result in aesthetically compromisedsmiles later in life.8,26 Some authors have recom-mended that the lower incisors rather than the upper incisors should be intruded to preserve smileaesthetics as the patient ages.8,22,23

Routine use of incisal edge – lip border measurementstaken with the lips at rest should be an important partof a diagnosis and subsequent treatment planning, notonly in orthodontics but also in other fields of dentistry.We have provided data on the appropriate positionsof the incisors to optimise dentofacial aesthetics in a wideage range of patients. Additional studies are needed, how-ever, to determine how a smile may change with age.

Conclusions

1. With increasing age, both genders show less oftheir upper incisors and more of their lower incisors.

DISPLAY OF INCISORS AS FUNCTIONS OF AGE AND GENDER


Table III. Age comparisons of upper and lower central incisor display.

Females Males

Group 2 Group 3 Group 4 Group 2 Group 3 Group 4

Upper central incisorsGroup 1 238.0 (<0.05) 56.5 (<0.01) 33.5 (<0.01) 224.0 (<0.01) 159.5 (<0.01) 8.5 (<0.01)Group 2 - 183.0 (<0.01) 91.0 (<0.01) - 355.0 (>0.05) 83.5 (<0.01)Group 3 - - 249.0 (<0.01) - - 205.0 (<0.01)

Lower central incisorsGroup 1 427.5 (>0.05) 117.0 (<0.01) 98.5 (<0.01) 378.5 (>0.05) 129.0 (<0.01) 56.0 (<0.01)Group 2 - 159.5 (<0.01) 124.5 (<0.01) - 222.0 (<0.01) 117.5 (<0.01)Group 3 - - 334.5 (>0.05) - - 228.0 (<0.01)

Mann-Whitney U test, p values in brackets, significant values in bold

2. Females display more of their upper incisors thanmales and males display more of their lower incisorsthan females.


Dr Andrea Fonseca Jardim da MottaAve. Engenheiro Martins Romeu n.41, apt.803Ingá, Niterói, RJBrazil CEP 24210-400Email: [email protected]

References 1. Kershaw S, Newton JT, Williams DM. The influence of

tooth colour on the perceptions of personal characteristicsamong female dental patients: comparisons of unmodified,decayed and ‘whitened’ teeth. Br Dent J 2008;204:pE9.

2. Eli I, Bar-Tal Y, Kostovetzki I. At first glance: social mean-ings of dental appearance. J Public Health Dent 2001;61:150–4.

3. Mack MR. Perspective of facial esthetics in dental treatmentplanning. J Prosthet Dent 1996;75:169–76.

4. Hulsey CM. An esthetic evaluation of lip-teeth relationshipspresent in the smile. Am J Orthod 1970;57:132–44.

5. Miller CJ. The smile line as a guide to anterior esthetics.Dent Clin North Am 1989;33:157–64.

6. Mackley RJ. ‘Animated’ orthodontic treatment planning. JClin Orthod 1993;27:361–5.

7. Sarver DM, Ackerman JL. Orthodontics about face: The re-emergence of the aesthetic paradigm. Am J OrthodDentofacial Orthop 2000;117:575–6.

8. Zachrisson BU. Esthetic factors involved in anterior toothdisplay and the smile: vertical dimension. J Clin Orthod1998;32:432–45.

9. Vig RG, Brundo GC. The kinetics of anterior tooth display.J Prosthet Dent 1978;39:502–4.

10. Peck S, Peck L, Kataja M. Some vertical lineaments of lipposition. Am J Orthod Dentofacial Orthop 1992;101:519–24.

11. Dickens ST, Sarver DM, Proffit WR. Changes in frontal softtissue dimensions of the lower face by age and gender. WorldJ Orthod 2002;3:312–20.

12. Al Wazzan KA. The visible portion of anterior teeth at rest.J Contemp Dent Pract 2004;5:53–62.

13. Arnett GW, Bergman RT. Facial keys to orthodontic diagno-sis and treatment planning. Part II. Am J OrthodDentofacial Orthop 1993;103:395–411.

14. McLaren EA, Rifkin R. Macroesthetics: facial and dentofa-cial analysis. J Calif Dent Assoc 2002;30:839–46.

15. Misch CE. Guidelines for maxillary incisal edge position-apilot study: the key is the canine. J Prosthodont 2008;17:130–4.

16. Burstone CJ. Lip posture and its significance in treatmentplanning. Am J Orthod 1967;53:262–84.

17. Zachrisson BU. Facial esthetics: guide to tooth positioningand maxillary incisor display. World J Orthod 2007;8:308–14.

18. Houston WJ. The analysis of errors in orthodontic measure-ments. Am J Orthod 1983;83:382–90.

19. Vig PS, Cohen AM. Vertical growth of the lips: a serialcephalometric study. Am J Orthod 1979;75:405–15.

20. Spear FM, Kokich VG, Mathews DP. Interdisciplinary man-agement of anterior dental esthetics. J Am Dent Assoc 2006;137:160–9.

21. Burstone CJ. Charles J. Burstone, DDS, MS. Part 1. Facialesthetics. Interview by Ravindra Nanda. J Clin Orthod2007;41:79–87.

22. Sarver DM. The importance of incisor positioning in theesthetic smile: the smile arc. Am J Orthod DentofacialOrthop 2001;120:98–111.

23. Sarver DM, Ackerman MB. Dynamic smile visualization andquantification: Part 1. Evolution of the concept and dynam-ic records for smile capture. Am J Orthod DentofacialOrthop 2003;124:4–12.

24. Lindauer SJ, Lewis SM, Shroff B. Overbite Correction andSmile Aesthetics. Semin Orthod 2005;11:62–6.

25. Fudalej P. Long-term changes of the upper lip position relative to the incisal edge. Am J Orthod DentofacialOrthop 2008;133:204–9.

26. Ackerman MB, Ackerman JL. Smile analysis and design inthe digital era. J Clin Orthod 2002;36:221–36.

MOTTA ET AL


Introduction

Cephalometric analysis is an important part of ortho-dontic diagnosis and treatment planning. It providesinformation on the relationships of the facial bonesand teeth not easily obtained by physical examin-ation. The usual method is to compare a variable inan individual with the same variable in an age-matched, representative sample. The informationgained can be used in communication with otherprofessionals and with patients. Some specialisedanalyses have been designed to compare different ethnic/racial or family groups, but the McNamaraanalysis, which is the subject of this communication,is a clinical analysis composed of eight linear and twoangular measurements.1 This analysis describes therelative positions of the maxillae and mandible, the length of the mandible, the height of the face and

the positions of the incisors. It has several limitations,such as reliance on linear measurements, which areinfluenced by magnification and may differ fromcephalostat to cephalostat, the use of unfamiliarmeasurements to describe the positions of the incisorsand no soft tissue measurements. In spite of these dis-advantages we have found that the measurements inthe analysis give a useful appraisal of dentofacial relationships, particularly for the age group likely torequire orthopaedic treatment.

As no norms for Turkish adolescents exist for theMcNamara analysis and eight out of 10 of the measurements in this analysis are affected by magni-fication, we decided to obtain norms for Turkish adolescents with well-balanced faces and Class Iocclusions, and to determine if there are gender differences in the measurements.


McNamara norms for Turkish adolescents withbalanced faces and normal occlusion

Nihat Kilic, Gülhan Catal and Hüsamettin OktayDepartment of Orthodontics, Faculty of Dentistry, Atatürk University, Erzurum, Turkey

Background: There are no norms for the McNamara analysis for Turkish adolescents.Objective: To obtain cephalometric standards for the McNamara analysis for Turkish adolescents with balanced faces andClass I occlusions, and to compare the standards with published data. Methods: The cephalometric radiographs of 116 children (83 female, 33 male) between 11 and 16 years of age with Turkishgrandparents and Class I occlusion, well-aligned upper and lower dental arches, no anterior and/or posterior crossbites andnormal dentofacial structures were used. The eight linear and two angular measurements in the McNamara analysis were meas-ured on images of the scanned radiographs. Measurements of the male and female subjects were compared with each otherand with published norms for North American adolescents and adults.Results: The Co-Gn, Co-A, ANS-Me and Ui-A were larger in the male subjects. Comparisons between the present study andMcNamara’s original study revealed that Anatolian Turkish adolescents, particularly girls, have smaller midfacial and mandibu-lar lengths and longer and more retrusive faces than North American adolescents and adults.Conclusions: The small, but statistically significant, gender differences in mandibular and midfacial lengths and lower anteriorface height may not be clinically significant. A single set of Turkish norms for the McNamara analysis may be appropriate.(Aust Orthod J 2010; 26: 33–37)

Received for publication: January 2009Accepted: November 2009

Nihat Kilic: [email protected]ülhan Catal: [email protected]üsamettin Oktay: [email protected]

KILIC ET AL



This study was approved by the Ethics CommitteeBoard of the School of Dentistry, Atatürk University.The material consisted of the lateral cephalometricfilms of 116 (83 female, 33 male) 11 to 16 year-oldTurkish adolescents with Turkish grandparents,selected from the longitudinal archive in theDepartment of Orthodontics, Faculty of Dentistry,Atatürk University. The mean ages of the girls andboys were 13.42 ± 1.13 years and 13.65 ± 1.47 years,respectively. The subjects had a Class I molar relationship, well-aligned upper and lower dentalarches with no/little crowding, no anterior and/orposterior crossbites and normal dental development.The radiographs of subjects with a history of previousorthodontic treatment, facial and/or dental trauma,systemic disease, subjective neuromuscular symptoms,symptoms of TMD, developmental and/or acquiredcraniofacial or neuromuscular deformities wereexcluded.

All radiographs were taken with the Frankfort planeparallel to the floor, the teeth in centric occlusion andthe lips at rest. The image enlargement was 8.7 percent and the data were not corrected for this enlarge-

Figure 1. The landmarks and measurements used in McNamara cephalometric analysis.11. A-N perpendicular (mm)2. Effective mandibular length (Co-Gn, mm)3. Effective midfacial length (Co-A, mm)4. Maxillo-mandibular difference (Mx-Md difference, mm)5. Lower anterior facial height (ANS-Me, mm)6. Mandibular plane angle (FH/MP, degrees)7. Facial axis angle (90˚ minus NBa-PtmGn, degrees)8. Pog-N perpendicular (mm)9. Ui-A (mm)10. Li-APog (mm)

Table I. McNamara cephalometric norms for 11-16 year-old Turkish children.

Variable Mean SD Minimum Maximum p

1. A-N perpendicular (mm) Female -0.44 2.52 -6.20 5.50 0.226Male 0.18 2.36 -3.50 5.30

2. Effective mandibular length (Co-Gn) (mm) Female 113.65 5.64 95.40 133.00 0.002Male 117.36 6.24 106.90 133.40

3. Effective Midfacial length (Co-A) (mm) Female 88.65 4.13 79.20 99.00 0.002Male 91.39 4.73 82.20 103.90

4. Maxillo-mandibular difference Female 24.86 3.39 13.30 32.70 0.127(Mx-Md diff) (mm) Male 25.97 3.87 18.70 32.80

5. Lower anterior facial height Female 66.66 4.16 56.60 76.10 0.003(ANS-Me) (mm) Male 69.43 4.84 59.10 79.60

6. Mandibular plane angle (FH/MP) (degrees) Female 25.01 3.65 16.40 33.30 0.983Male 25.02 3.22 17.90 32.70

7. Facial axis angle (90˚minus Female -1.93 3.89 -11.60 9.90 0.594NBa-PtmGn) (degrees) Male -2.34 3.38 -9.80 4.60

8. Pog-N perpendicular (mm) Female -4.79 4.55 -15.50 4.90 0.342Male -3.92 4.29 -13.10 3.70

9. Ui-A (mm) Female 3.15 2.15 -3.70 6.70 0.022Male 4.19 2.22 0.50 10.90

10. Li-APog (mm) Female 1.67 2.28 -3.70 6.90 0.073Male 2.48 1.92 -0.50 7.00


ment. The films were scanned with an EpsonExpression 1860 Pro scanner (Seiko EpsonCorporation, Japan) and the resulting images (100per cent) were digitised and measured using QuickCeph 2000 (Quick Ceph Systems, San Diego, CA,USA). The landmarks and measurements inMcNamara analysis are shown in Figure 1.1

Statistical analysisTo determine the measurement errors, 15 randomlyselected radiographs were remeasured by the sameexaminer two weeks after the initial measurements.The reliability of the measurements was assessed withintra-class correlation coefficients.2 Student’s t-testswere used to compare the measurements in the boysand girls, and to compare the measurements in theTurkish boys and girls with the norms published byMcNamara.1 All statistical analyses were performedusing the SPSS software package (SPSS for Windows98, version 10.0, SPSS Inc., Chicago, IL, USA).

Results

The reliability coefficients exceeded 0.90 for all measurements, indicating that the measurementscould be reliably repeated.

Comparisons of the measurements in the girls andboys are given in Table I. The effective mandibularlength (Co-Gn), effective midfacial length (Co-A),lower anterior facial height (ANS-Me) and the dis-tance from the labial surface of the most prominentupper central incisor to the perpendicular to theFrankfort line through A point (Ui-A) were signifi-cantly larger in the boys. The lower incisors in theboys were almost 1 mm further behind the A-Pog linethan the lower incisors in the girls, but the differencewas not statistically significant (p = 0.073).

The means of the female and male Turkish adoles-cents were compared with the 14 year-old adolescentsin the Bolton and Burlington studies and the adultsin the Ann Arbor study reported by McNamara(Table II).1 The Turkish girls had significantly more

MCNAMARA NORMS FOR TURKISH ADOLESCENTS


Table II. Comparisons of the means with published norms.

Parameters Present Bolton Burlington Ann Arbor study (14 years)1 (14 years)1 (Adults)1

1. A-N perpendicular (mm) Female -0.44 a -0.4 aMale 0.18 -1.1

2. Effective mandibular length (Co-Gn) (mm) Female 113.65 c 118.9 c 114.9Male 117.36 120.6 119.2

3. Effective midfacial length (Co-A) (mm) Female 88.65 a,c 92.1 c 89.2 aMale 91.39 b1,b2 95.2 b1 93.9 b2

4. Maxillo-mandibular difference (Mx-Md diff) (mm) Female 24.86 26.7 25.7Male 25.97 25.3 25.3

5. Lower anterior facial height (ANS-Me) (mm) Female 66.66 65.6 66.2Male 69.43 66.8 68.8

6. Mandibular plane angle (FH-MP) (degrees) Female 25.01 c -22.7 cMale 25.02 c -21.3 c

7. Facial axis angle (90˚ minus NBa-PtmGn) (degrees) Female -1.93 c -0.2 cMale -2.34 c -0.5 c

8. Pog-N perpendicular (mm) Female -4.79 c -1.8 cMale -3.92 c -0.3 c

9. Ui-A (mm) Female -3.15 4.2Male -4.19 3.8

10. Li-APog (mm) Female -1.67 1.4Male -2.48 1.4

a, p < 0.05; b, p < 0.01; c, p < 0.001Image enlargement: present study 8.7 per cent; McNamara’s study 8.0 per cent

KILIC ET AL


retruded maxillae (A-N perp, p < 0.05) than the AnnArbor adults, and significantly shorter mandibles(Co-Gn, p = 0.001) than the 14 year-old Americangirls in the Bolton study, but not the Canadian girlsin the Burlington study. The midfacial lengths (Co-A) in the Turkish girls and boys were shorterthan the same lengths in the adolescents in the Boltonand Burlington studies. The Turkish adolescents alsohad significantly steeper mandibular plane angles(FH/MP) than the Ann Arbor adults (Females, p < 0.001; Males, p < 0.001). The facial axis angle(90º minus NBa-PtmGn), the angle between thenasion-basion line and the constructed line from thepostero-superior aspect of the pterygomaxillary fissueto gnathion subtracted from 90 degrees, was signifi-cantly less in Turkish adolescents compared with theadolescents in the Ann Arbor study (Females, p < 0.001; Males, p < 0.001). The mandibles (Pog-Nperp) in the Turkish adolescents were also 3 to 3.5mm more retruded than the mandibles in the AnnArbor adults. There were no significant differencesbetween the positions of the upper and lower incisors(Ui-A distance, Li-APog distance) in the Turkish adolescents and the samples reported by McNamara.1

Discussion

We used the lateral cephalometric radiographs ofTurkish adolescents with well-balanced faces to estab-lish clinical norms for the McNamara analysis. Thisanalysis uses relatively few measurements to describethe dental and skeletal relationships of interest toorthodontists and maxillofacial surgeons. We foundthat the girls in our sample had slightly shorter mid-facial (Co-A) and mandibular lengths (Co-Gn) andshorter lower anterior face heights (ANS-Me) thanthe boys in our sample. The differences were small,ranging from slightly over 1 mm in the case of Ui-Ato almost 4 mm in the case of Co-Gn and very vari-able. Because different ethnic groups can have differ-ent morphological features we wanted our sample tobe representative of the children we treat. Therefore,we chose adolescents with Class I occlusions andTurkish grandparents attending our clinic for treat-ment and in the same age group as the majority ofour patients. Besides sharing a common culture andlanguage, individuals in an ethnic group often have asimilar dentofacial morphology that sets them apartfrom other groups.3 However, many countries such asTurkey contain several different ethnic groups andseparate norms may be required for each group.

We were primarily interested in providing norms forthe McNamara analysis, which appraises dentofacialskeletal relationships. We selected individuals withclose-to-ideal occlusal relationships and no visibledentoskeletal anomalies because we wanted to use thenorms for orthodontic diagnosis and treatment plan-ning for patients attending our clinic. Unlike manyother orthodontic analyses the McNamara analysisrelates the maxillae, mandible and incisors to verticalfacial planes: the principal one is the perpendicularline to the Frankfort plane passing through nasion.Although this analysis avoids some of the problemsassociated with more widely used ANB angle fordetermining skeletal relationships, it relies on linearmeasurements that may vary with age and with thecephalostat used. The SNA angle increases approxi-mately 1 degree from 6 to 18 years of age, and a 1 degree change at point A is equivalent to a 1 mmlinear change in the position of point A relative tonasion.4 Furthermore, analyses that have linear meas-urements are not popular because separate norms orcorrection factors are required for cephalostats withdifferent image enlargements. However, we were for-tunate that the image magnification of our cephalo-stat was 8.7 per cent, which closely matches the 8 percent image enlargement in McNamara’s study.1

Previous studies have reported significant differencesin the dentofacial relationships of Turkish and non-Turkish children.5–7 We found that the midfaces ofthe Turkish girls were slightly less protrusive than theNorth American adults reported by McNamara, andthat the girls and boys in our sample had slightlylonger faces (FH/MP, 90º minus NBa-PtmGN, Pog-N perp) than the North American adults.1 These dif-ferences may be due to growth and/or maturationalchanges in the North American sample or method-ological differences.8 In contrast to our findings,Bassciftci et al., who also used the McNamara analysis,reported there were no significant differences in theA-N perpendicular distance, effective mandibularand midfacial lengths between his sample of Turkishadults and North American adults.1,8 Gazilerli6 andCeylan and Gazilerli7 also reported that Turkish chil-dren had retrusive faces compared with Americanchildren.

Generally boys have larger dentofacial measurementsthan girls, although the differences may not be clini-cally significant. The concept of clinical significancein cephalometric studies has yet to become widely

adopted. We found the mean gender differences forCo-A, Co-Gn and ANS-Me were around 3–4 mm. Inagreement with Ioi et al.,9 Basciftci et al.8 andSwlerenga et al.10 we found that the mandibularlength (Co-Gn), midfacial length (Co-A) and loweranterior face height (ANS-Me) were significantlylarger in the boys. Our differences ranged from 2.74mm for Co-A to 3.71 mm for Co-Gn. On the otherhand, Wu et al.,11 who also used the McNamaraanalysis, reported that only midfacial length andlower anterior facial height were larger in maleChinese subjects. Ioi et al.9 reported that measure-ments of Pog-N perpendicular in Japanese andCaucasian males were -6.8 mm and -0.3 mm, respec-tively; and the effective mandibular lengths (Co-Gn)were 130.40 mm and 134.3 mm, respectively. Thedifferences were statistically significant, indicatingthat Japanese have more retruded facial profiles thanCaucasians.

Conclusions

The small, but statistically significant, gender differences in mandibular and midfacial lengths,lower anterior face height and upper incisor protru-sion may not be clinically significant. A single set ofTurkish norms for the McNamara analysis may beappropriate.


Dr Nihat KilicAtatürk Üniversitesi Dis Hekimligi FakültesiOrtodonti Anabilim Dalı 25240 ErzurumTurkeyEmail: [email protected]: +90 442 2311810Fax: +90 442 2312270 - 2360945

References1. McNamara Jr JA. A method of cephalometric evaluation.

Am J Orthod 1984;86:449–69. 2. Houston WJ. The analysis of errors in orthodontic measure-

ments. Am J Orthod 1983;83:382–90.3. Richardson ER. Racial differences in dimensional traits of

the human face. Angle Orthod 1980;50:301–11.4. Riolo ML, Moyers RE, McNamara JA, Hunter WS. An atlas

of craniofacial growth: cephalometric standards from theUniversity School growth study. Monograph No. 2,Craniofacial Growth Series, Center for Human Growth andDevelopment, University of Michigan, Ann Arbor. 1974;23–373.

5. Gulyurt M. Ricketts' frontal cephalometric measurements inthe children of Erzurum region. Türk Ortodonti Derg1989;2:144–51.

6. Gazilerli Ü. (Thesis) Seiner norms of Ankara Children withnormal occlusion aged between 13–16 years. AnkaraUniversity, Faculty of Dentistry, Department of Dento-maxillo-facial Orthopedics. Ankara, 1976.

7. Ceylan I, Gazilerli Ü. A comparison of Steiner, Downs andTweed measurements of the children living Erzurum areawith other some groups. J Dental Faculty Ankara University.1992;19:143–52.

8. Basciftci FA, Uysal T, Buyukerkmen A. Craniofacial struc-ture of Anatolian Turkish adults with normal occlusions andwell-balanced faces. Am J Orthod Dentofacial Orthop 2004;125:366–72.

9. Ioi H, Nakata S, Nakasima A, Counts AL. Comparison ofcephalometric norms between Japanese and Caucasian adultsin antero-posterior and vertical dimension. Eur J Orthod2007;29:493–9.

10. Swlerenga D, Oesterle LJ, Messersmith ML. Cephalometricvalues for adult Mexican-Americans. Am J OrthodDentofacial Orthop 1994;106:146–55.

11. Wu J, Hägg U, Rabie AB. Chinese norms of McNamara'scephalometric analysis. Angle Orthod 2007;77:12–20.

MCNAMARA NORMS FOR TURKISH ADOLESCENTS


Introduction

Pre-adjusted self-ligating edgewise orthodontic brack-ets are claimed to be accurately manufactured to eachmanufacturer’s prescription, allowing a tooth to bemoved predictably in three dimensions. There haslong been an assumption that the quoted dimensionsof bracket slots are indeed accurate. In fact, severalstudies have shown discrepancies between the pub-lished and actual dimensions of orthodontic brackets.1–3

The importance of accurately published dimensionsof bracket slots was underlined by Kusy and Whitley.4They emphasised that clinicians should be aware ofthe exact dimensions so that the critical contact anglefor binding can be calculated. This angle is thought tobe important for the efficient treatment of patients, as

binding and the resistance to sliding mechanics canoccur if the contact angle between the archwire andbracket increases, but it can be somewhat compen-sated for by the use of slightly oversized brackets andundersized archwires.

The aims of this study were to measure the slotdimensions of 0.022 inch self-ligating upper centralincisor brackets from six manufacturers, to comparethe measured dimensions with the manufacturers’published dimension of 0.022 inch, and to determineif the walls of the slots were parallel.

Materials and method

Five randomly selected, upper left central incisor0.022 x 0.028 inch self-ligating brackets from the


Assessment of slot sizes in self-ligating bracketsusing electron microscopy

Nidhi B. Bhalla,* Sarah A. Good,+ Fraser McDonald,* Martyn Sherriff†

and Alex C. Cash±

Department of Orthodontics, King’s College Hospital;* ‘Guys and St Thomas’ NHS Foundation Trust, London,+ Department of Biomaterials,King’s College London Dental Institute† and the Queen Victoria Hospital, East Grinstead,± United Kingdom

Objective: To measure the slot dimensions of 0.022 inch self-ligating upper central incisor brackets from six manufacturers usingelectron microscopy, to compare the measured dimensions with the manufacturers’ published dimensions, and to determine ifthe walls of the slots were parallel.Materials: Six self-ligating upper central incisor brackets from four manufacturers (SmartClip and Clarity SL, 3M Unitek,Monrovia, CA, USA; Speed, Strite Industries Ontario, Canada; Damon MX, Ormco, Orange, CA, USA; In-Ovation R and In-Ovation C, Dentsply GAC, Bohemia NY, USA) were imaged with a scanning electron microscope and the slots heightsmeasured. Intra-operator repeatability and accuracy were determined.Results: All brackets had slot sizes that were significantly larger (p < 0.05) than the stated 0.022 inch. Speed brackets were5.1 per cent larger (0.02311 inch) and the closest to the published dimension. The SmartClip brackets were 14.8 per centlarger (0.02526 inch) than the quoted slot size of 0.022 inch. In most brackets the distances between the slot walls was generally greater further from the bracket bases.Conclusions: The actual measurements of upper central incisor self-ligating brackets from six manufacturers were larger than themanufacturers’ stated dimension, and the walls of the slots diverged from the bracket bases.(Aust Orthod J 2010; 26: 38–41)

Received for publication: March 2009Accepted: November 2009

Nidha Bhalla: [email protected] Good: [email protected] McDonald: [email protected] Sherriff: [email protected] Cash: [email protected]

ASSESSMENT OF SLOT SIZES IN SELF-LIGATING BRACKETS USING ELECTRON MICROSCOPY


following manufacturers were used: SmartClip andClarity SL (3M Unitek, Monrovia, CA, USA); Speed(Strite Industries Ontario, Canada) (Figure 1);Damon MX (Ormco, Orange, CA, USA); In-Ovation R (Figure 2) and In-Ovation C (DentsplyGAC, Bohemia, NY, USA).

The brackets were mounted on electron microscopestubs with conductive putty with the self-ligatingspring or clip either fully open or removed to providea clear view of the slot walls. They were orientated onthe stubs so that the mesio-distal axes of the bracketslots were perpendicular to the bases of the stubs andthe microscope table. The putty allowed the bracketsto be manipulated in the electron microscope toensure that the edges of the slots could be imaged.Non-metallic brackets were sputter-coated with goldto a thickness no greater than 20 nm in order to allowaccurate scanning and measurement.

Each bracket was scanned individually in the scan-ning electron microscope (Hitachi S-3500N HighTechnologies Corporation, Berkshire, UK) to pro-duce an image from which digital measurementscould be taken. Images were captured, saved as TIFFImages and exported to Quartz PCI 5.1 (QuartzImaging Corporation, Vancouver, Canada). The dis-tances or heights between the walls of the slots weremeasured on x100 images and compared to thedimensions published by each manufacturer.

Data were analysed using the statistical package Stata10.0 (StataCorp 2003, College Station, TX, USA).Significance was predetermined at a level of α = 0.05.

Student’s t-test was used to compare the slot heights.The method errors were determined using a standardcalibration chart prior to measurements being taken,and the measurements were repeated two weeks later.The successive measurements were accurate andrepeatable to greater than 99 per cent.

Results

The results are given in Tables I and II.

The mean slot heights ranged from 0.02311 inch forthe Speed brackets to 0.02526 inch for the Smartclipbrackets (Table I). Smartclip brackets were the mostvariable in slot size (SD: 0.00073 inch) and In-Ovation R brackets the most consistent in size (SD:0.00021 inch). The discrepancies ranged from 5.1per cent for the Speed brackets to 14.8 per cent forthe SmartClip brackets (Table II).

All brackets were statistically significantly larger than 0.022 inch and most brackets had divergent slot walls: the distance between the slot walls wasgenerally greater further from the bracket base.

Discussion

Although the results of this study agree with previousstudies of the slot sizes of conventional brackets, ouruse of electron microscopy has enabled a high degreeof accuracy of measurement. We found the slot sizesof self-ligating brackets to be significantly larger thanthe manufacturers’ quoted size of 0.022 inch and theslot walls to diverge from the base of the slot. The

Figure 1. Speed bracket (Original magnification x100). Figure 2. In-Ovation R bracket (Original magnification x100).

slots in brackets from the same manufacturer mayvary in size as well.2,3

Manufacturing and material parameters affect theamount of play in the torque dimension.2 Fischer-Brandies et al. measured five commercially availablearchwires and brackets with computer-aided lightmicroscopy and reported that although the bracketswere on average 0.8 per cent larger than the dimen-sions quoted by the manufacturers, the archwires hadsignificantly smaller cross-sections.2 The slot – archwire difference was thought to be a major con-tributor to torque play. This rather large discrepancy,as compared to the findings of our study, may be afunction of the relative accuracy of the two measure-ment techniques or, indeed, the different bracketsmeasured.

The greatest amount of play is in the torque plane.5When using a full-sized archwire, there is still a 6-degree loss of torque, as calculated from bracketslot size tolerances, but this can extend to 100 percent torque loss in a low torque prescription.6 Theseare theoretical calculations that do not necessarily

represent actual values. For ease of use and patientcomfort it has been suggested that some play betweenthe wire and slot walls is reasonable,1 providingtorque to teeth such as the upper incisors is not com-promised. Incorrectly torqued teeth may affect thefinal occlusion, anterior tooth guidance and space inthe arch.

The method of manufacture affects the accuracy ofthe slot walls and contributes to loss of torque.Brackets cast from moulds are affected by shrinkageand milling introduces various imperfections such asgrooves and striations and uncovers porosity in theslot walls. To compensate for manufacturing imper-fections and to ensure that the imperfections do notinterfere with archwire engagement, manufacturersdeliberately increase the slot dimensions and bevelthe edge of archwires.1 Torque-induced stresses suchas notching of the internal surface of walls of a brack-et slot further increase bracket – wire play. Fischer-Brandies et al.2 suggested these stresses can lead to afurther 0.016 mm widening of bracket slots. Weshould, however, expect manufacturers to producebrackets and wires to accurate dimensions as these arevariables that can be controlled.

The effects of manufacturing inaccuracies on the clinical performance of orthodontic appliances hashighlighted the need for a regulatory body, supportedby an appropriate legal framework, that ensures min-imum standards of these devices. The German toler-ance limits published in 2000 specify the tolerancelimits for orthodontic bracket slots should be nomore than 0.056 ± 0.04 mm.7 The AmericanStandards Association 2004 also stipulated theirbracket tolerances for slot height must be within0.0025 mm.8 The Medical and Healthcare ProductsRegulatory Agency (MHRA), set up in April 2003, is

BHALLA ET AL


Table I. The measured slot heights of self-ligating brackets, in inches.

Bracket Mean (Inch) SD (Inch) Minimum Maximum p

In-Ovation R 0.02385 0.00021 0.02362 0.02417 0.001SmartClip 0.02526 0.00073 0.02390 0.02626 0.001Speed 0.02311 0.00026 0.02260 0.02358 0.001Damon MX 0.02478 0.00033 0.02429 0.02516 0.001Clarity SL 0.02409 0.00043 0.02331 0.02472 0.001In-Ovation C 0.02450 0.00060 0.02362 0.02547 0.001

Significant values in boldProbability associated with the t - test for slot height = 0.022 inch

Table II. Percentage differences between the measured bracket heightsand quoted height of 0.022 inch.

Per cent > 0.022 inch

Speed 5.1In-Ovation R 8.4Clarity SL 9.5In-Ovation C 11.4Damon MX 12.6SmartClip 14.8

ASSESSMENT OF SLOT SIZES IN SELF-LIGATING BRACKETS USING ELECTRON MICROSCOPY


the UK government agency responsible for ensuringthat medical devices work and are acceptably safe.The MHRA have produced specific regulatory guidance for manufacturers of dental appliances andprostheses. The Medical Devices Directive providesguidelines, which enable manufactured devices tomeet the requirements set. Some dental appliances,made to specific prescriptions, may be defined as custom-made devices and the requirements of theMedical Devices Directive will apply to those whowish to manufacture these products.9

Conclusions

1. The slot heights of upper left central incisor self-ligating brackets from six manufacturers were greaterthan the manufacturers’ stated dimension of 0.022inch. The differences ranged from 5.1 per cent larger(Speed) to 14.8 per cent larger (SmartClip) than the0.022 inch dimension published.

2. There was considerable variation in slot sizesbetween different bracket systems.

3. The walls of the slots diverged from the bracketbases.

Acknowledgments

We wish to thank Ken Brady and the staff in theElectron Microscopy Suite, King’s College Hospital,for all their help and advice with this study.


Dr Nidhi BhallaDepartment of OrthodonticsKing’s College HospitalDenmark HillLondon SE5 9RSUnited KingdomTel: 01483 571 122 Ext 4444Email: [email protected]

References1. Kusy RP, Whitley JQ. Assessment of second-order clearances

between orthodontic archwires and bracket slots via the critical contact angle for binding. Angle Orthod 1999;69:71–80.

2. Fischer-Brandies H, Orthuber W, Es-Souni M, Meyer S.Torque transmission between square wire and bracket as afunction of measurement, form and hardness parameters. JOrofac Orthop 2000;61:258–65.

3. Cash A, Good SA, Curtis RV, McDonald F. An evaluation ofslot size in orthodontic brackets – are standards as expected?Angle Orthod 2004;74:450–3.

4. Kusy RP, Whitley JQ. Influence of archwire and bracketdimensions on sliding mechanics: derivations and determin-ations of the critical contact angles for binding. Eur JOrthod 1999;21:199–208.

5. Creekmore TD, Kunik RL. Straight wire: the next gener-ation. Am J Orthod Dentofacial Orthop 1993;104:8–20.

6. Sebanc J, Brantley WA, Pincsak JJ, Conover JP. Variabilityof effective root torque as a function of edge bevel on ortho-dontic arch wires. Am J Orthod 1984;86:43–51.

7. German Standards Tolerance Limits. January 2000.8. American National Standards/American Dental Association

Specification No. 100 Orthodontic Brackets and Tubes.2004.

9. EC Medical Devices Directives. Medicines and Healthcareproducts Regulatory Agency. Directive 93/42/EEC. UpdatedMarch 2008.

Introduction

Orthodontics is mainly a cosmetic specialty of dentistry focused on the diagnosis, interception, andtreatment of malocclusions and associated facialappearance. The ideal orthodontic result is to com-plete treatment by moving the teeth into stable andaesthetically pleasing positions, without compromis-ing their health either in the short- or long-term. Inorder to achieve this we need an accurate and thorough clinical evaluation and diagnosis.1 Theaccurate assessment of crowding and/or spacerequirements is a major part of this planning process;the majority of the current populations seeking

orthodontics require treatment of crowding to relievethe misalignment of the teeth.1,2

Space assessment can be undertaken in both the per-manent and the mixed dentitions. Mixed dentitionspace analysis is a method that predicts the mesio-distal widths of the unerupted permanent canines andpremolars in patients still awaiting the exfoliation ofprimary teeth. Part of this analysis may identify a periodof space maintenance, regaining space already lost bymesial migration, eruption guidance or serial extraction.

Conversely, the space requirements can be evalu-ated by a permanent dentition analysis when the permanent dentition is fully erupted (the permanent


Space planning sensitivity and specificity: RoyalLondon Space Planning and Korkhaus Analyses

Rania Dause, Martyn Cobourne and Fraser McDonaldDepartment of Orthodontics, King’s College London Dental Institute, London, United Kingdom

Objectives: To establish the sensitivity and specificity of the Korkhaus and Royal London Space Planning Analyses.Methods: The sample consisted of 30 cases with two sets of study models and lateral cephalometric radiographs taken at leastthree years apart. These were then further subdivided into Class I (N = 10), Class II division 1 (N = 10) and Class II division 2cases (N = 10). The Royal London Space Planning Analysis and the Korkhaus Analysis were applied on these cases at bothtimes.Results: Study model analysis: The Royal London Planning Analysis revealed that in Class I malocclusions, upper and lower archcrowding and spacing changed significantly with time. The total space required and tooth size reduction for the lower archhad also changed significantly. Additionally, in the Class II division 1 malocclusions, lower arch crowding and spacing, totalspace required and the need for tooth size reduction had significantly increased, while, in Class II division 2 malocclusions, astatistically significant increase was observed in the upper and lower arch crowding and spacing.The Korkhaus Analysis showed that in Class I malocclusions a significant decrease was observed in the lower arch length andthe lower anterior arch width. The upper posterior (inter-molar) arch width had significantly increased. In Class II division 1 mal-occlusions the lower right posterior space available had decreased significantly. The upper posterior arch width and the lowerposterior arch width also significantly increased. In Class II division 2 malocclusions, a statistically significant decrease wasobserved in the lower anterior arch length. There were no significant changes in all angular and the two linear measurementsfor all classes. Conclusions: The Royal London Space Planning Analysis and the Korkhause Analysis are clinically sensitive analyses. The RoyalLondon Space Planning Analysis lacks specificity to be a robust model for treatment planning; modification may be requiredbefore this technique is accepted. (Aust Orthod J 2010; 26: 42–48)

Received for publication: July 2009Accepted: December 2009

Rania Dause: [email protected] Cobourne: [email protected] McDonald: [email protected]

ROYAL LONDON SPACE PLANNING AND KORKHAUS ANALYSES


dentition often excludes the eruption of the thirdmolars).3 One of the methods used to assess spaceand formalise the process of treatment planning is theRoyal London Space Planning Analysis.4,5 It is a protocol that incorporates space analysis with treatment planning and is undertaken as part of thetreatment planning process after detailed clinicalexamination, cephalometric analysis,6,7 and studymodel analysis. It tries to establish a disciplinedapproach to diagnosis and treatment planning and it provides clinicians with a record to justify treat-ment decisions for professional accountability anddetermines whether the treatment objectives areachievable.4,5 In brief, this process is carried out intwo stages. The first stage calculates the total spacerequired in each dental arch to attain the treatmentobjectives. These include measuring the crowdingand spacing, levelling the occlusal curve, arch widthchanges, incisor A/P changes and upper incisor angu-lation/inclination. The second stage calculates anyadditional space to be created or utilised includingtooth reduction/enlargement, extractions, spaceopening for a bridge/implant, molar distal move-ment, molar mesial movement and differential maxillary/mandibular growth.

Space planning measures those aspects of a malocclu-sion and proposed treatment that either consume orcreate space.4,5 Space utilisation included aligning

crowded teeth, opening space for bridges, toothenlargement, mesial movement, arch constriction,incisor retraction, palatal apical incisor torque andlevelling the occlusal curve. Space creation includedextraction, enamel reduction, distal movement, archexpansion, incisor advancement and labial apical incisor torque. The total space consumed should beequal to the total space created such that neitherspace excess nor deficiency is present at the end of thespace planning process. This is known as a zeroresidue. This information can be used to decide theneed for extraction, plan anchorage management,plan the mechanics for correction of arch relation-ships and identify whether the treatment objectives ormechanics are to be modified.4,5

On the other hand, the Korkhaus analysis is a tech-nique designed to provide an accurate assessment forthe space requirements. This analysis requires a specific kit, which includes an orthometer, dividersand sliders (Figure 1). The orthometer is a device thatconsists of a central white plastic disc with anengraved scale and four windows, which rotatearound a scale, revealing numbers that represent dif-ferent dimensions. The divider is used to measure thetooth and arch widths. The sliders are transparentplastic discs with engraved scales that are used for castand radiograph analysis.

In brief, the width of the four central incisors aremeasured with the dividers, this value is then trans-ferred to the SJ window (this includes a range of normal values representing the sum of the mesio-distal widths of all central incisors) on the ortho-meter. The orthometer provides us with the requiredvalues of the anterior arch length and width and pos-terior arch width. Then, using dividers, the spaceavailable in the anterior arch length and width andthe posterior width are measured on the dental casts.The difference between the space available and thespace required indicates the total amount of crowd-ing/spacing, which are vital in the process of treatment planning.

Treatment in the permanent dentition, whetherinclusive of crowding or spacing, can be carried outby one of the following methods: dental crowdingcan be treated by interproximal reduction,8,9 archexpansion, inter-maxillary mechanics, extractionswith or without anchorage support,10 or surgically;dental spacing can be treated by either closing thosespaces or relocating them.11

Figure 1. Korkhaus analysis kit (orthometer, divider and sliders).

This study aimed to evaluate two methods of spaceanalysis using untreated cases of different malocclu-sions. The two techniques, the Korkhaus and RoyalLondon Space Analyses, both have limitations, butwe aimed to compare the two techniques to establishif they were robust clinical adjuncts to treatmentplanning.

Materials and methodsStudy sampleThis study used serial records collected by the lateProfessor Leighton. The collection consists of therecords of 1095 reportedly untreated subjects whohad been followed from 1952 until the present. Weused the lateral skull radiographs and the study models collected in the Leighton study.

The following selection criteria were used:

1. No evidence of treatment. This could be:

a. Extractions: this was validated by examination ofthe study casts and, when required, the panoramicradiograph.

b. Use of fixed appliances: this was determined by theimpression of brackets on the teeth of the study models.

c. Use of removable appliances: there were seven caseswhere the study model box had a significant numberof removable appliances which fitted the study models, and extra-oral appliances.

d. There was a small number of cases (< 20) where thealignment of teeth on the final study models wasinconsistent with normal development, as judged byan experienced clinician.

2. Permanent dentition.

3. Class III malocclusions were excluded becausethere were insufficient cases.

The final sample was 30 cases with pairs of lateralcephalometric radiographs and study models repre-senting various types of malocclusion and differentlevels of crowding: Class I (N = 10; 6 males, 4females), Class II division 1 (N = 10; 5 males, 5females) and Class II division 2 cases (N = 10; 6males, 4 females). The records of each case wereselected at two different ages with a minimum ofthree years apart. The mean age of the subjects at theinitial records was 12 years, 10 months (Range: 12years 5 months to 13 years 10 months) and at the

second set of records it was 16 years 2 months(Range: 15 years 6 months to 17 years 7 months).

MethodsThe cephalometric radiographs were traced and theangular and distance measurements in the Eastmancephalometric analysis used to determine if changesoccurred in the inclinations of the incisors or theskeletal relationships.12,13

The two stages in the Royal London Space PlanningAnalysis were applied to the paired study models todetermine the total space required and the amount ofspace created/utilised in each dental arch.4,5

The Korkhaus Analysis was then applied to thematching study models in which anterior arch length,anterior and posterior arch widths and the spaceavailable for the posterior teeth were measured.

Error study methodTen randomly selected sets of records that were notpart of this study were measured twice with a twoweek interval between measurements, by the sameexaminer. There was no systemic error and there wereno significant differences between the first and second measurements.

Statistical method All statistical analyses were carried out using SPSS15.0 for Windows (Statistics Package for the SocialSciences).13 The T1 and T2 means and standard devi-ations for each reading and the differences betweenthe T1 and T2 readings were calculated. Paired t-testswere used to determine the significant differencesbetween the two ages. The statistical significance wasset at the probability level of 0.05.

Results

The Royal London Space Analysis (Table I) revealedthat in Class I malocclusion, crowding and spacing inthe upper and lower arches changed significantly(Mean T1: -0.10; Mean T2: -1.10, p = 0.004). Thetotal space required and tooth size reduction for thelower arch has also changed significantly (Mean T1: -0.80; Mean T2: -2.10, p = 0.033). In Class II division1 the lower arch crowding and spacing (Mean T1: -1.30; Mean T2: -2.30, p = 0.004), total space required(Mean T1: -1.10; Mean T2: -2.20, p = 0.007) and theneed for tooth size reduction (Mean T1: 1.80; Mean

DAUSE ET AL




T2: 2.40, p = 0.024) has significantly increased. InClass II division 2 malocclusions statistically signifi-cant increases were observed in the upper and lowerarch crowding and spacing (Mean T1: -1.20; MeanT2: -2.40, p = 0.003).

There were no significant cephalometric changes forall classes from T1 to T2. The detailed results areshown in Table II.

The Korkhaus Analysis (Table III) showed that inClass I malocclusion a significant decrease wasobserved in the lower arch length (Mean T1: 16.05;Mean T2: 15.60, p = 0.041) and the lower anteriorarch width (Mean T1: 36.05; Mean T2: 35.45,

p = 0.018). The upper posterior (inter-molar) archwidth significantly increased (Mean T1: -4.40; MeanT2: -4.90, p = 0.015). In the Class II division 1 group,the lower right posterior space available has decreasedsignificantly (Mean T1: 21.25; Mean T2: 20.65, p =0.030). The upper posterior arch width (Mean T1:47.05; Mean T2: 47.50, p = 0.041) and the lowerposterior arch width (Mean T1: 45.40; Mean T2:46.15, p = 0.003) have significantly increased. InClass II division 2 a statistically significant decreasewas observed in the lower anterior arch length (MeanT1: 15.51; Mean T2: 14.85, p = 0.026). Additionally,there were no significant changes in the posterior archwidth found in the Class II division 2 malocclusions.

Table I. Comparisons of the Royal London Space Planning from T1 to T2.

Upper arch Lower archComponents Mean difference SD difference p Mean difference SD difference p

Class I Crowding and spacing 1.00 0.82 0.004 1.20 1.23 0.013Incisor A/P change 0.10 0.74 0.678 0.10 0.88 0.726Total space required 0.81 1.77 0.182 1.30 1.64 0.033Tooth reduction/enlargement -1.20 1.87 0.074 -0.80 1.03 0.037

Class II division 1 Crowding and spacing 1.10 1.73 0.075 1.00 0.82 0.004Incisor A/P change 0.90 3.66 0.457 0.00 0.47 1.000Total space required 2.10 4.63 0.185 1.10 0.31 0.007Tooth reduction/enlargement -0.10 2.08 0.882 -0.60 0.70 0.024

Class II division 2 Crowding and spacing 1.20 0.92 0.003 0.80 0.92 0.022Incisor A/P change -0.90 1.37 0.068 -0.20 1.23 0.619Total space required -0.10 1.85 0.868 0.50 1.27 0.244

All measurements in mmPaired t - test, statistically significant values in bold

Table II. Comparisons of the cephalometric measurements from T1 to T2.

Class I Class II division 1 Class II division 2Mean SD Mean SD Mean SD

difference difference p difference difference p difference difference p

SNA – SNA2 -0.50 1.92 0.389 -0.80 1.99 0.235 0.00 1.70 1.000SNB – SNB2 -0.85 1.20 0.052 -0.95 1.38 0.058 -0.45 2.43 0.573ANB – ANB2 0.20 1.32 0.642 0.10 1.29 0.811 0.40 1.58 0.443SNMx – SNMx2 0.40 3.24 0.705 0.70 1.34 0.132 0.60 1.35 0.193MxMP – MxMP2 0.40 2.50 0.389 1.10 3.00 0.276 0.90 2.02 0.193UISN – UISN2 -0.55 1.83 0.117 -0.10 3.84 0.936 -0.90 2.85 0.343UIMxP – UIMxp2 -1.00 2.91 0.305 0.70 3.40 0.531 -0.60 2.72 0.502UI-APg – UI-APg2 -0.35 0.82 0.209 -0.10 1.74 0.860 0.30 1.00 0.370LIMP – LIMP2 0.10 2.56 0.904 -0.80 2.10 0.259 1.80 5.39 0.319LIAPg – LIAPg2 -0.10 0.91 0.735 -0.05 1.21 0.899 -0.15 2.33 0.843

Discussion

The sample consisted of 30 cases with two sets ofrecords (study models and lateral cephalometric)taken on two occasions at least three years apart. Thecases were derived from the Leighton collection toevaluate the sensitivities and specificities of theKorkhaus Analysis and the Royal London SpacePlanning Analysis. By definition, sensitivity is theproportion of positives correctly identified by the test and specificity is the proportion of negatives correctly identified by the test.14

The intercanine and intermolar widths, and archlength were significantly reduced in the present studyin all malocclusions when assessed using theKorkhaus analysis. These findings were consistentwith previous studies.15–17 Bishara and coworkersassessed several parameters including arch widths andlength as well as crowding and space requirements ina sample from Iowa Longitudinal Growth Study.15

They found an increase in crowding and as a resultspace requirements as well as a reduction in archwidths and lengths. The decrease in mandibular archlength was significantly greater in the male subjects ascompared with the female subjects (p < 0.001). Thisparameter is of great clinical value as it holds a long-term implication on the retention and stability of

orthodontic treatment. This has been shown by Littleand other investigators.18,19 Little and Riedel havereviewed records of 31 subjects at 10 and 20 yearspost-retention. They found that arch widths andlength decreased after the retention period whereascrowding increased. Only 10 per cent of the subjectswere considered to retain an acceptable alignmentafter 20 years post-retention.19

The present study showed statistically significantchanges in the amount of crowding and spacerequirements using both analyses. These were expected dental changes with normal growth anddevelopment of the dentofacial complex.17,20

However, correlating the two parameters is complexin nature. Several other factors were considered in theliterature to play a role in the changes that occur tothe mixed and permanent dentitions.17,20 Incisorcrowding was linked to factors such as: the character-istics of the dentition and the discrepancy betweenthe mesiodistal and buccolingual dimensions of theincisors, physiological forces such as mesial drift, andthe uprighting of mandibular incisor with growth ofthe mandible.18,19 In agreement with others webelieve though that the overriding factor in crowdingand space requirement is the reduction in arch widthsand length.21,22

DAUSE ET AL


Table III. Comparisons of the Korkhaus Analysis from T1 to T2.

Upper arch Lower archMean SD Mean SD

difference difference p difference difference p

Class I Anterior arch length 0.50 0.91 0.117 0.45 0.60 0.041Anterior arch length difference -0.50 1.08 0.117 0.70 0.95 0.045Anterior arch width 0.30 0.95 0.343 0.60 0.66 0.018Posterior arch width 0.35 0.78 0.191 0.25 1.40 0.586Posterior arch width difference 0.50 0.53 0.015 0.50 1.43 0.299

Class II division 1 Anterior arch length 0.10 0.74 0.678 0.60 1.49 0.234Anterior arch width -0.25 1.11 0.495 0.20 0.79 0.443Right posterior space available 0.25 0.49 0.138 0.60 0.74 0.030Posterior arch width -0.45 0.60 0.041 -0.75 0.59 0.003Posterior arch width difference -0.70 1.06 0.066 -0.90 1.20 0.041

Class II division 2 Anterior arch length 0.60 0.88 0.058 0.66 0.78 0.026Anterior arch width 0.55 1.55 0.292 0.35 0.63 0.111Posterior arch width 0.00 0.82 1.000 -0.15 1.16 0.691

Measurements in mmPaired t - test, statistically significant values in bold

In the current study, it was observed that crowdingwas more pronounced in Class II division 2 subjectswhen compared to Class I and Class II division 1 sub-jects. This is clearly related to the greater reduction inarch widths and length, which featured in the Class IIdivision 2 subjects. These significant changes may beattributed to the fact that Class II division 2 mal-occlusion is characterised by reduced vertical pro-portions, which would influence the amount ofcrowding and arch length changes as the mandibularincisors tend to tip lingually in low angle subjects.

The ability of both analyses to identify dental changessuch as crowding, arch width and arch length reduc-tion that occur with growth and development of thecraniofacial complex clearly shows a good sensitivityfor the Korkhaus and the Royal London SpaceAnalyses.

However, the problems initially identified with theRoyal London Space Planning Analysis as it is cur-rently described do not take into consideration mid-line correction and arch asymmetries. These are clearly significant areas that need consideration fortreatment planning and should be factored intoorthodontic treatment decisions.23 By definition,‘dental midline’ is the midsagittal line of maxillaryand mandibular dental arches. Each arch has its ownmidline. The upper incisor midline should coincidewith that of the maxilla and the lower incisor midlineshould coincide with that of the mandible.24 Whilstdental arch asymmetry is defined as the imbalancebetween left and right sides of the jaws in terms ofshape/archform and occlusion, this can be due to aunilateral crossbite.23

The Royal London Space Planning Analysis is reli-able, but it’s specificity is questionable.25 As it appearsthat, like most other space planning techniques, the

Royal London Space Planning Analysis is unable toidentify and quantify growth imbrications (Figure 2).This is clearly demonstrated in the inability of theanalysis to predict differential growth of dento-alveolar complex and mesial drift of the buccal segment.

Cephalometric analysis showed no significantchanges in the angular and linear measurements forall classes from T1 to T2. One reason may be attrib-uted to the fact that radiographs, unlike study models,are two-dimensional views of a three-dimensionalstructure. For example, it is not possible to calculateor observe the changes in arch widths using a lateralcephalometric radiograph. Another reason would bethe fact that some of the subjects had past theirgrowth spurts and as a result any changes would be of small magnitude and, therefore, would not be significant.

It is also apparent that there are different require-ments of treatment planning for differing incisal relationships i.e. Class I, Class II division 1 and ClassII division 2 relationships. There appears no clear orrobust consideration of the differing growth changesthat may influence the outcome of treatment asdependent on the incisal relationship and the under-lying growth pattern.

Conclusion

The present study demonstrated an increase in theanterior crowding and a decrease in the total archlength and arch widths. The Royal London SpacePlanning Analysis and the Korkhaus Analysis are clin-ically sensitive analyses in that they identified thischange. As anticipated, the Royal London SpacePlanning Analysis was unsuccessful in indicating thegrowth imbrications, which would have adverseimplications on the treatment planning process. TheRoyal London Space Analysis lacks specificity to be afully robust model for treatment planning; modifica-tion may be required prior to the complete accept-ance of this technique to identify factors that are notincorporated within its basic calculations. Clearlythere is need for further clarification if such a methodis to be developed.

The present work sheds light on the clinical value oftwo processes in space planning. However, the samplewas relatively small. It is recommended that the studyis repeated with more subjects to increase the reliabil-ity, minimise the bias and improve the validity of theoutcomes.



Figure 2. An example of a Class II division 1 case showing anterior pointdisplacement from the time of T1 (left) to T2 (right).

DAUSE ET AL



Dr Rania R. DauseDepartment of OrthodonticsFloor 22, Tower WingKing’s College London Dental InstituteSt Thomas StLondon SE1 9RTUnited KingdomEmail: [email protected]

References1. Proffit William R. Contemporary Orthodontics. St. Louis;

Mosby, 2007;195–218.2. Mockers O, Aubry M, Mafart B. Dental crowding in a pre-

historic population. Eur J Orthod 2004;26:151–6.3. Shellhart WC, Lange DW, Kluemper GT, Hicks EP, Kaplan

AL. Reliability of Bolton tooth-size analysis when applied tocrowded dentitions. Angle Orthod 1995;65:327–34.

4. Kirschen RH, O’Higgins EA, Lee RT. The Royal LondonSpace Planning: an integration of space analysis and treat-ment planning: Part I: Assessing the space required to meettreatment objectives. Am J Orthod Dent Orthop 2000a;118:448–55.

5. Kirschen RH, O’Higgins EA, Lee RT. The Royal LondonSpace Planning: an integration of space analysis and treat-ment planning: Part II: The effect of other treatment pro-cedures on space. Am J Orthod Dent Orthop 2000b;118:456–61.

6. Brown M. Eight methods of analysing a cephalogram toestablish anteroposterior skeletal discrepancy. Br J Orthod1981;8:139–46.

7. Paskow H. Self-alignment following interproximal stripping.Am J Orthod 1970;58:240–9.

8. Abu Alhaija ES, Al-Khateeb SN, Al-Nimri KS. Prevalence ofmalocclusion in 13–15 year-old North Jordanian schoolchildren. Community Dent Health 2005;22:266–71.

9. Chate RA. The burden of proof: a critical review of ortho-dontic claims made by some general practitioners. Am JOrthod Dent Orthop 1994;106:96–105.

10. Chaimattayompol N, Wong SX. Diagnostic management ofinterdental spacing. J Prosthet Dent 2000;84:467–9.

11 Mills JR. The application and importance of cephalometryin orthodontic treatment. Orthodontist 1970;2:32–47.

12. Jacobson A. Radiographic cephalometry: from basics tovideo-imaging. Quintessence Publishing Co. Inc., 1995;53–63.

13. The Statistics Package for the Social Sciences website.http://www.spss.com

14. Altman DG. Practical statistics for medical research.London: Chapman and Hall, 1991;409–19.

15. Bishara SE, Jakobsen JR, Treder JE, Stasi MJ. Changes in themaxillary and mandibular tooth size-arch length relationshipfrom early adolescence to early adulthood. A longitudinalstudy. Am J Orthod Dent Orthop 1989;95:46–59.

16. Bishara SE, Treder JE, Jakobsen JR. Facial and dentalchanges in adulthood. Am J Orthod Dent Orthop 1994;106:175–86.

17. Lundström A. Changes in crowding and spacing of the teethwith age. Dent Pract Dent Rec 1969;19:218–24.

18. Little RM, Wallen TR, Riedel RA. Stability and relapse ofmandibular anterior alignment-first premolar extractioncases treated by traditional edgewise orthodontics. Am JOrthod 1981;80:349–65.

19. Little RM, Riedel RA. An evaluation of changes in man-dibular anterior alignment from 10 to 20 years postre-tention. Am J Orthod Dent Orthop 1988;93:423–8.

20. Thilander B. Dentoalveolar development in subjects withnormal occlusion. A longitudinal study between the ages of5 and 31 years. Eur J Orthod 2009;31:109–20.

21. O’Higgins EA, Lee RT. How much space is created fromexpansion or premolar extraction? J Orthod 2000;27:11–13.

22. O’Higgins EA, Kirschen RH, Lee RT. The influence of max-illary incisor inclination on arch length. Br J Orthod 1999;26:97–102.

23. Langberg BJ, Arai K, Minerc RM. Transverse skeletal anddental asymmetry in adults with unilateral lingual posteriorcrossbite. Am J Orthod Dent Orthop 2005;127:6–16.

24. Jerrold L, Lowenstein LJ. The midline: diagnosis and treat-ment. Am J Orthod Dent Orthop 1990;97:453–62.

25. Al-Abdallah M. Sandler J. O’Brien K. Is the Royal LondonSpace Analysis reliable and does it influence orthodontictreatment decisions? Eur J Orthod 2008;30:503–7.

IntroductionRapid maxillary expansion (RME) is often used tocorrect a transverse maxillary deficiency. DuringRME the mid-palatal suture is widened and the twomaxillae forced apart by an appliance anchored to thebuccal teeth. Following expansion, bone is depositedin the mid-palatal suture.1–4 It is well-known thateven after a period of retention the expanded maxil-lae can ‘rebound’ to their original positions, in somecases by as much as 90 per cent.5–7

Deposition of bone in the expanded suture starts atthe end of active treatment phase and continues for60 to 90 days.8,9 Although the reason for the post-expansion relapse is not fully understood, the qualityand rapidity of bone deposited in the mid-palatalsuture during and after expansion may influence therelapse.1 It could be postulated that accelerated boneformation in the suture after expansion may reducethe amount of time required for retention and prevent the maxillae from relapsing.1,2


Response of the expanded inter-premaxillarysuture to intermittent compression. Early bone changes

Tancan Uysal,* Huseyin Olmez,† Mihri Amasyali,† Yildirim Karslioglu,+ Atilla Yoldas±

and Omer Gunhan+

Department of Orthodontics, Erciyes University, Kayseri, Turkey and the King Saud University, Riyadh, Saudi Arabia,* Departments ofOrthodontics† and Pathology+ Gülhane Military Medical Academy, Ankara and the Veterinary Research and Control Institute, Adana,± Turkey

Objective: To determine the response of the expanded premaxillary suture in the rat to an externally applied force. Specifically,to investigate early bone changes in the expanded suture to intermittent loading and unloading.Methods: Twenty-four 50 to 60 day-old Wistar rats were assigned to three groups. The inter-premaxillary sutures in all animalswere expanded with a 50 g force applied to the upper incisors. Group I served as the control, whereas in Groups II and III the incisors were subjected to intermittent loading and unloading after five days of expansion. The intermittent forces were produced by a cam (0.416 mm, 100 cycles per minute) applied to the disto-gingival margins of the upper incisors. Themechanical stimuli were applied daily over nine days for six seconds in Group II (30 grams force, 10 cycles/day) and 10 minutes in Group III (30 grams force, 1000 cycles/day). Bone regeneration in the suture was evaluated histomorpho-metrically. The area of new bone (µm2), the perimeter around the new bone (µm), Feret’s diameter (µm) and the percentage ofnew bone to non-ossified tissue (%) were measured and compared.Results: Statistically significant differences were found between the groups for all histomorphometric parameters. New bonearea (p < 0.001), bone perimeter (p < 0.001), Feret’s diameter (p < 0.001) and percentage of new bone (p < 0.001) weresignificantly larger in the experimental groups as compared with the Control group. The histomorphometric measurements confirmed that more new bone was deposited in the sutures subjected to intermittent loading and unloading. Conclusion: The application of cyclic loading and unloading to the orthopaedically expanded inter-premaxillary suture during the early retention phase stimulated the formation of new bone. (Aust Orthod J 2010; 26: 49–55)

Received for publication: July 2009Accepted: January 2010

Tancan Uysal: [email protected] Olmez: [email protected] Amasyali: [email protected] Karslioglu: [email protected] Yoldas: [email protected] Gunhan: [email protected]

UYSAL ET AL


Attempts to shorten the healing period in a healingfracture or distraction callus may throw further lighton the relapse that follows maxillary expansion.Various methods have been used to stimulate the dep-osition of new bone in a fracture callus. Deminer-alised bone matrix, autologous marrow cells or cul-tured periosteal cells have been transplanted into thedistracted area and bone formation in the callus hasbeen stimulated either mechanically, electrically orelectromagnetically.10–16 Micro-movements appliedexternally to a callus may result in the early formationof new bone which also happens to be ‘stronger’.17–23

Recent evidence suggests that cyclic compression maybe more beneficial than cyclic distraction, but the evi-dence is by no means clear-cut.21–23 The aim of thisexperimental study was to evaluate the effects ofexternally applied, intermittent compression on boneregeneration in the expanded inter-premaxillarysuture in the rat.

Material and methodsAnimalsTwenty-four male 50 to 60 day-old Wistar rats with amean weight of 210.63 ± 20.95 g were used. All ani-mals were housed in polycarbonate cages, subjectedto a 12-hour light – dark cycle at the constant tem-perature of 23 °C and fed a standard pellet diet(Expanded pellets, Stepfield, Witham, Essex, UK)with tap water ad libitum. Permission was obtainedfrom the Gulhane Military Medical Academy, EthicsCommittee of Experimental Animals after theResearch Scientific Committee at the same institu-tion had approved the experimental protocol. Theexperiments were carried out in the Department ofExperimental Animals, Research and DevelopmentCenter, Gulhane Military Medical Academy.

Appliance placementThe animals were anaesthetised with an intra-muscular injection of Xylasine (Bayer, Istanbul,Turkey) and Ketamine (Parke-Davis, Istanbul,Turkey) at 0.5 ml/kg and 1 ml/kg body weight,respectively. The expansion appliances were helicalsprings fabricated from 0.014 inch stainless steel wireinserted in holes drilled close to the gingival marginsof both upper incisors. The springs were activated to deliver a force of 50 g and were not reactivatedduring the 5-day expansion period.

After five days the springs were removed and replacedwith short lengths of rectangular retaining wire.Tooth separation was maintained for 10 days. Thedistance between the mesial edges of the upper incisors was measured at the beginning of the experi-ment and at the end of expansion with a digitalcaliper (MSI-Viking Gage, SC, USA).

Application of intermittent compression The animals were randomly allocated to three groupswith eight rats in each group. The animals in GroupI were not subjected to intermittent compression andserved as the control. In Groups II and III, intermit-tent compression was applied at the disto-gingivalmargins of the upper incisors 24 hours after five daysof expansion and continued for a further nine days.The intermittent compressive loads (100/minute)were produced by a cam with an amplitude of 0.416mm operated by an electrical motor. Intermittentcompression was applied by two acrylic pads placedon the disto-gingival margins of the incisors for sixseconds in Group II (30 grams force, 10 cycles/day)and 10 minutes in Group III (30 grams force, 1000cycles/day). The stimuli were applied daily from thesecond to the seventh day of retention.

Specimen preparationAfter the retention period of 10 days, the rats weresacrificed with an overdose of Ketamine and Xylasineand their premaxillae were dissected out and fixed in10 per cent formalin. After fixation, the retainingwires were removed and the premaxillae were decalci-fied with 5 per cent formic acid for three days. Afterdecalcification, the premaxillae were cut into blockswith one cut passing through the incisor crowns atthe alveolar crest and perpendicular to the sagittalplane, the second cut 4 mm apical to the first cut.The sections were rinsed, trimmed and embedded inparaffin. The paraffin blocks were sectioned serially at5 µm intervals.

Histomorphometric analysisThe histological sections were stained with haema-toxylin and eosin (Figure 1). The histomorphometricmeasurements were performed 200 µm beneath theoral surface of the osseous palate because bone for-mation in the surface layer was sometimes irregularand unsuitable for quantitative measurement. Thesections were viewed under a microscope (Olympus

CX41/DP25 Research System, Olympus Corpor-ation, Japan) and the histomorphometric measure-ments were calculated with an image analysis programme.

The histomorphometric measurements were per-formed by two assessors who were blinded to theidentity of the sections. The final results are averagesof these separate evaluations. Two histological sections from each animal were analysed and repre-sentative areas, which were defined beforehand, werecaptured at x400 magnification. The image analysissoftware, Image-J (US National Institutes of Health,Bethesda, MA, USA) was used to compute the histo-morphometric measurements.24 The followingparameters were measured: new bone area (µm2),bone perimeter (µm), Feret’s diameter (µm) and percentage of new bone. These basic planimetricmeasurements provided a description of the amountof new bone. The new bone area is the total cross-sectional area of new bone. The bone perimeter andFeret’s diameter are the length of the perimeteraround the new bone and the maximum distancebetween any two points on the perimeter, respec-tively. Two separate image analysis macro-programmes were written by one of the authors(Y.K.) to increase the contrast between the bone andsurrounding tissue and display the basic plani-metric measurements of the outlined new bone

(Figure 2). The second macro enhanced each imageand superimposed a grid, consisting of squares withareas of 1000 µm2, on the image. Intersections of thegrid superimposed on new bone were recorded. Afterrecording the new bone, non-ossified areas wererecorded in the same manner. At the end of themacro, the programme calculated the percentage ofnew bone (Figure 3).

Statistical analysisStatistics were analysed with the Statistical Packagefor Social Sciences 13.0 (SPSS for Windows, SPSSInc, Chicago, IL, USA). A non-parametric test, theKruskal-Wallis one-way analysis of variance was usedto compare the groups and a one-sided Mann-Whitney U test was used to determine which groups

RESPONSE OF THE EXPANDED INTER-PREMAXILLARY SUTURE TO INTERMITTENT COMPRESSION


Figure 1. Histological section of an expanded suture (H&E, x40 magnification).

Figure 2. Measurement of an outlined area of new bone (µm2).

Figure 3. The number of grid intersections on new bone and non-osseousconnective tissue were counted and the percentage of new bone calculated.

UYSAL ET AL


were significantly different. Probability values lessthan 0.05 were accepted as significant.

Results

All animals survived to the end of the study. Deepmucosal infections, dehiscences or other adverseeffects were not observed in any animals. The expan-sion appliances were well-tolerated and the animalsgained weight. Two rats in Group II and one rat inGroup III lost weight during retention, but subse-quently gained weight. As no statistically significantchanges in body weight were found during the expan-sion and retention periods there was no reason toweight-correct the data.

The histological sections confirmed that the inter-premaxillary sutures were expanded in all groups andthere was no statistically significant difference (p = 0.071) in the amount of expansion in the groups.The ANOVA analysis did, however, show significantdifferences between the groups for the area of newbone, the bone perimeter, Feret’s diameter and thepercentage of new bone formed (Table I).

With regard to the areas of new bone, the highestvalue was observed in Group III (Mean: 130.96 ±19.85 µm2) and the lowest value in Group I (Mean:57.64 ± 19.98 µm2) and the difference between thesegroups was statistically significant (p < 0.001).Significant differences were also found between

Groups I and II (p < 0.001) and Groups II and III (p = 0.05) (Figures 4 and 5).

The perimeters around the islands of new bone inGroups I and II, I and III, and II and III were signif-icantly different (Table I). The mean perimeteraround the new bone in Group III (Mean: 193.83 ±19.18 µm) was significantly longer than the meanperimeter in Group I (Mean: 137.08 ± 15.21 µm) (p < 0.001) and Group II (Mean: 178.20 ± 14.76µm) (p = 0.039). The mean bone perimeter measure-ments in Group I and Group II were also significantlydifferent (p < 0.001).

Statistically significant differences were foundbetween Feret’s diameters in Groups I and II (p <0.001) and Groups I and III (p < 0.001). No signifi-cant difference was found between Groups II and III.

The greatest percentage of new bone was found inGroup III (Mean: 70.14 ± 8.26 per cent) and the low-est percentage of new bone in Group I (Mean: 34.86±11.89 per cent) and the difference was statisticallysignificant (p < 0.001). A significant difference wasalso found between Groups I and II (p < 0.001).

Discussion

To our knowledge, this study is the first to report thatexternally applied intermittent compression increasedbone healing in the expanded inter-premaxillary

Table I. Comparisons of the histomorphometric measurements.

Multiple comparisons (p)Parameters Group N Mean SD SE Minimum Maximum p Group II Group III

Area (µm2 ) I 8 57.64 19.98 7.55 28.90 89.57 0.000 0.000 0.000II 8 104.51 14.15 5.34 84.67 129.60 0.012III 8 130.96 19.85 3.72 112.55 142.04

Perimeter (µm) I 8 137.07 15.21 1.96 82.47 236.19 0.000 0.000 0.000II 8 178.20 14.76 1.79 125.55 232.21 0.039III 8 193.83 19.18 3.46 163.71 289.71

Feret's diameter (µm) I 8 15.21 19.59 7.40 12.08 17.15 0.000 0.000 0.000II 8 59.81 14.78 5.58 42.87 76.11 NSIII 8 66.06 13.28 1.24 22.77 103.39

Newly formed bone (%) I 8 34.86 11.90 4.49 20.00 55.55 0.000 0.001 0.000II 8 58.78 10.35 3.91 44.44 76.34 NSIII 8 70.14 8.26 3.12 60.00 84.84

Significant values in boldNS, not significant

suture in the rat. More new bone was deposited in theexpanded suture following intermittent compressionthan in the control suture, leading to a moreadvanced stage of healing.

There have been several reports in the orthopaedic literature that an intermittent mechanical force stimulates the formation of new bone, but in theorthodontic literature few studies have been carriedout to stimulate regeneration in the mid-palatal/inter-premaxillary suture after expansion.1,2 Recently,we investigated the effects of dietary boron in rabbitsand locally administered ED-71 on bone formationin the mid-palatal suture in rats, and found that theseagents stimulated bone regeneration during theexpansion and retention periods.3,4

During expansion a multi-factorial adaptive responsetakes place in the mid-palatal suture. Mechanicalexpansion disrupts the orderly sutural structure andinduces a chain of events that restore the suture to itsoriginal architecture.25 In the present study, we followed the sutural response to intermittent compression histomorphometrically: a method that provides reliable quantitative information on bone remodelling in experimental and in-vitro conditions.1–4,26

The width of the normal inter-premaxillary suture inyoung rats is approximately 20–60 µm.27 Burstoneand Shafer28 determined that expansion of the sutureover a period of five days ‘opened’ the suture, on aver-age, 380 ± 10 µm. Our springs achieved slightly less

opening (between 297.17 and 371.23 µm) after fivedays. Although we found no difference between thegroups in the amount of expansion, the histo-morphometric parameters (i.e. area of new bone,perimeter around the new bone, Feret’s diameter andthe percentage of new bone to non-ossified tissue)were significantly less in the Control group, indicat-ing that new bone deposited along the sutural mar-gins had reduced the widths of the inter-premaxillarysutures in the experimental groups. Intermittentcompression of the edges of the expanded premaxillaepresumably resulted in some force (compressionand/or relaxation) being transferred to the healing tissues in the suture in spite of the retaining wire.

Animals have been used to study the effects of forceon the rates of bone formation in the craniofacialsutures. While monkeys and cats have similar maxil-lary sutures to man and have been used in maxillaryexpansion experiments, rabbits and rats are less costly and give a clear picture of the changes in asuture under stress.27 In view of the ethical and costconsiderations, we chose the rat to investigate theeffects of mechanical stimulation on bone modelling.

The optimal mechanical stimulation to acceleratebone healing has not been determined. To date, stud-ies have focused on the magnitude of the micro-movement (i.e. the amplitude) and the delay beforeloading. Several reports indicate that immediate andearly mechanical interventions are the most effective,while other authors have suggested that a short delay



Figure 4. A Group III specimen (Intermittent compression, 1000 cycles/day),showing large amounts of new bone, indicating a later stage of bone forma-tion (HE, x200 magnification). O, old bone; W, expanded suture; N, newbone; C, well-organised fibrous connective tissue.

Figure 5. A Group I specimen (Control group) showing the beginning ofbone formation (HE 200X magnification). A, old bone; B, osteoblastic area;C, connective tissue, containing some inflammatory cells.

may be necessary to allow neurovascularisation tooccur.29–32 We decided on the latter course of actionand applied an intermittent mechanical force to thepremaxillae 24 hours after the expansion.

Similar uncertainty exists concerning the frequencyand magnitude of loading on bone healing. Forexample, a wide range of load and strain magnitudeshave been studied in sheep models.20,33 Some investi-gators were able to both enhance and inhibit bonehealing with different combinations of the timing ofload initiation and load amplitude.16 It appears that astronger callus occurs if axial cyclic compression isapplied after a short delay and at a low load ampli-tude.16 For this reason we used a low load amplitudeof only 30 grams (the expansion force was 50 grams)and applied the force after a short delay.

It is uncertain whether it is the compressive or dis-tractive displacements that enhance new bone for-mation.23 There appears to be a critical number ofloading cycles necessary to enhance new bone forma-tion: in a fractured bone increasing the number ofloading cycles above the critical value did not result inmore new bone.34 We found significant histomor-phometric differences in bone area and perimeterbetween the Groups II and III (in both cases theGroup II findings were less than the Group III find-ings) which suggests that high loading cycles mayenhance bone formation in the inter-premaxillarysuture.

Conclusion

The application of cyclic micromovements to theexpanded inter-premaxillary suture during the earlyphase of retention stimulates bone formation andimproves healing. Future studies will investigatewhether additional loading cycles enhance new boneformation in inter-premaxillary suture in the rat.

Acknowledgments

This work was supported by a research grant fromGulhane Military Medical Academy ResearchScientific Committee (AR-2009-05).


Dr Tancan UysalErciyes UniversitesiDis Hekimligi FacultesiOrtodonti Anabilum Dall, 38039

MelikgaziKayseriTurkeyEmail: [email protected]

References1. Saito S, Shimizu N. Stimulatory effects of low-power laser

irradiation on bone regeneration in midpalatal suture duringexpansion in the rat. Am J Orthod Dentofacial Orthop1997;111:525–32.

2. Sawada M, Shimizu N. Stimulation of bone formation in the expanding mid-palatal suture by transforming growthfactor-beta 1 in the rat. Eur J Orthod 1996;18:169–79.

3. Uysal T, Ustdal A, Sonmez MF, Ozturk F. Stimulation ofbone formation by dietary boron in an orthopedicallyexpanded suture in rabbits. Angle Orthod 2009;79:984–90.

4. Uysal T, Amasyali M, Enhos S, Sonmez MF, Sagdic D. Effectof ED-71, a new active vitamin D analog, on bone forma-tion in an orthopedically expanded suture in rats. A histo-morphometric study. Eur J Dent 2009;3:165–72.

5. Krebs AA. Midpalatal suture expansion studied by theimplant method over a seven-year period. Trans Eur OrthodSoc 1964;131–42.

6. Vardimon AD, Graber TM, Voss LR. Stability of magneticversus mechanical palatal expansion. Eur J Orthod 1989;11:107–15.

7. Timms DJ. Long term follow-up of cases treated by rapidmaxillary expansion. Trans Eur Orthod Soc 1976;52:211–15.

8. Haas AJ. The treatment of maxillary deficiency by openingthe midpalatal suture. Angle Orthod 1965;35:200–17.

9. Cleall JF, Bayne DI, Posen JM, Subtelny JD. Expansion ofthe midpalatal suture in the monkey. Angle Orthod 1965;35:23–35.

10. Hagino T, Sato H, Yokoyama Y, Akamatsu N. Shortening ofbone union in limb lengthening. J Jpn Orthop Assoc1995;64: 928.

11. Hamanishi C, Yoshii T, Totani Y, Tanaka S. Lengthened callus activated by axial shortening: Histological and cyto-morphometrical analysis. Clin Orthop Relat Res 1994;307:250–4.

12. Tsubota S, Tsuchiya H, Shinokawa Y, Minematsu K, TomitaK. Osteoblast-like cell transplantation to the distracted callus. J Jpn Soc External Fixation 1997;81–B:125–9.

13. Kassis B, Glorion C, Tabib W, Blanchard O, Pouliquen J.Callus response to micromovement after elongation in therabbit. J Pediatr Orthop 1996;16:480–3.

14. Pepper JR, Herbert MA, Anderson JR, Bobechko WP. Effectof capacitive coupled electrical stimulation on regeneratebone. J Orthop Res 1996;14:296–302.

15. van Roermund PM, ter Haar Romeny BM, Hoekstra A,Schoonderwoert GJ, Brandt CJ, van der Steen SP et al. Bonegrowth and remodelling after distraction epiphysiolysis ofthe proximal tibia of the rabbit: Effect of electromagneticstimulation. Clin Orthop Relat Res 1991;266:304–12.

16. Gardner MJ, van der Meulen MC, Demetrakopoulos D,Wright TM, Myers ER, Bostrom MP. In vivo cyclic axialcompression affects bone healing in the mouse tibia. JOrthop Res.2006;24:1679–86.

17. Claes LE, Heigele CA, Neidlinger-Wilke C, Kaspar D, SeidlW, Margevicius KJ, Augat P. Effects of mechanical factors onthe fracture healing process. Clin Orthop Relat Res 1998;355:S132–S47.

UYSAL ET AL


18. Goodship AE, Kenwright J. The influence of induced micro-movement upon the healing of experimental tibial fractures.J Bone Joint Surg Br 1985;67:650–5.

19. Kenwright J, Richardson JB, Cunningham JL, White SH,Goodship AE, Adams MA, Magnussen PA, Newman JH.Axial movement and tibial fractures. A controlled random-ized trial of treatment. J Bone Joint Surg Br 1991;73:654–9.

20. Claes LE, Heigele CA. Magnitudes of local stress and strainalong bony surfaces predict the course and type of fracturehealing. J Biomech 1999;32:255–66.

21. Augat P, Merk J, Wolf S, Claes L. Mechanical stimulation byexternal application of cyclic tensile strains does not effec-tively enhance bone healing. J Orthop Trauma 2001;15:54–60.

22. Matsushita T, Kurokawa T. Comparison of cyclic compres-sion, cyclic distraction and rigid fixation. Bone healing inrabbits. Acta Orthop Scand 1998;69:95–8.

23. Hente R, Füchtmeier B, Schlegel U, Ernstberger A, PerrenSM. The influence of cyclic compression and distraction onthe healing of experimental tibial fractures. J Orthop Res2004;22:709–15.

24. Rasband WS. Image-J, U.S. National Institutes of Health,Bethesda, Maryland, USA, http://rsb.info.nih.gov/ij/,1997–2008.

25. Chang HN, Garetto LP, Potter RH, Katona TR, Lee CH,Roberts WE. Angiogenesis and osteogenesis in an orthope-dically expanded suture. Am J Orthod Dentofacial Orthop1997;111:382–90.

26. Eriksen EF, Axelrod DW, Melson F. Bone Histology andHistomorphometry. In: Bone Histomorphometry. New York:Raven Press, 1994:33–8.

27. Storey E. Tissue response to the movement of bones. Am JOrthod 1973;64:229–47.

28. Burstone CJ, Shafer WG. Sutural expansion by controlledmechanical stress in the rat. J Dent Res 1959;38:534–40.

29. Miclau T, Lu C, Thompson Z, Choi P, Puttlitz C, MarcucioR et al. Effects of delayed stabilization on fracture healing. JOrthop Res 2007;25:1552–8.

30. Klein P, Schell H, Streitparth F, Heller M, Kassi JP,Kandziora F et al. The initial phase of fracture healing isspecifically sensitive to mechanical conditions. J Orthop Res2003;21:662–9.

31. Bailón-Plaza A, van der Meulen MC. Beneficial effects ofmoderate, early loading and adverse effects of delayed orexcessive loading on bone healing. J Biomech 2003;36:1069–77.

32. Claes L, Eckert-Hübner K, Augat P. The effect of mechani-cal stability on local vascularization and tissue differen-tiation in callus healing. J Orthop Res 2002;20:1099–105.

33. Mark H, Nilsson A, Nannmark U, Rydevik B. Effects offracture fixation stability on ossification in healing fractures.Clin Orthop Relat Res 2004;419:245–50.

34. Rubin CT, Lanyon LE. Regulation of bone formation byapplied dynamic loads. J Bone Joint Surg Am 1984;66:397–402.



Introduction

The traditional view is that facial morphology andthe positions of the incisors are determined to a largeextent by the resting posture and activity of the oro-facial musculature, and in particular the lower lip.1This view is supported by evidence that the electro-myographic activities of the orbicularis oris musclesin the lower lips of subjects with Class I, Class II division 1 and Class II division 2 malocclusions areassociated with the inclinations of the incisors.2However, significant associations between elec-tromyographic activity in the lower lip musculatureand the inclinations of the incisors, overjet and over-bite were not found in subjects with a normal bite oran anterior open bite.3 Associations between muscleactivity in the upper lip and dentoalveolar morph-ology have not received the same attention, althoughthere is some evidence that the orbicularis oris musclein the upper lip may be active in children with anatypical swallowing pattern and incompetent lips.4Furthermore, some reports have suggested that the force exerted by the upper lip may influence the inclination of the upper incisors.5

The purpose of the present study is to determine ifmuscle activity in the upper lip, specifically in theorbicularis oris muscle, is associated with the inclin-ations of the upper and lower incisors, overjet andoverbite.


The 45 subjects (29 girls, 16 boys) in this investi-gation were randomly selected from those withcrowding, increased or decreased overjet or overbite,spacing, flared or retruded incisors who applied to theDepartment of Orthodontics, Faculty of Dentistry,Atatürk University for orthodontic treatment. Themean ages of girls and boys were 13.56 ± 1.04 and13.47 ± 0.91 years, respectively. Thirty-two subjectshad dental and skeletal Class I malocclusions, sevensubjects had Class II malocclusions and six subjectshad Class III malocclusions. The subjects had com-petent lips and no developmental and/or acquiredcraniofacial or neuromuscular deformities, no sys-temic disease, no history of orthodontic treatment,no signs or symptoms of temporomandibular jointdisorder (TMD) and no habits such as an abnormal


Associations between upper lip activity and incisor position

Nihat KilicDepartment of Orthodontics, Faculty of Dentistry, Atatürk University, Erzurum, Turkey

Background: Muscle activity in the upper lip may influence the positions of the upper and lower incisors.Objective: To determine the associations between muscle activity in the upper lip and the inclinations of the incisors, overjetand overbite.Methods: Forty-five subjects (29 girls, 16 boys), between 11 and 15 years of age with predominantly Class I malocclusion,were used. The inclinations of the incisors, overjet and overbite were measured on lateral cephalometric radiographs. Bipolarelectrodes were placed on the upper lip to record the activity in orbicularis oris muscle at rest, during maximal clenching, chew-ing hazelnuts and swallowing. Correlation coefficients between the cephalometric variables and the electromyographic (EMG)activity in the upper lip were calculated.Results: There was no gender difference in the EMG activity in the upper lip. There were no statistically significant associationsbetween the EMG activities in the upper lip and the inclinations of the incisors, overjet and overbite.Conclusions: The positions of the incisors do not appear to be influenced by muscle activity in the upper lip. (Aust Orthod J 2010; 26: 56–60)

Received for publication: March 2009Accepted: January 2010

Nihat Kilic: [email protected]

ASSOCIATIONS BETWEEN UPPER LIP ACTIVITY AND INCISOR POSITIONS


swallowing pattern, finger or thumb sucking. Thematerials used in this study were the lateral cephalo-metric radiographs and EMG records of the subjects.This study was approved by the Ethics CommitteeBoard of the School of Dentistry, Atatürk University,and the parents of all subjects gave their informedconsent.

The lateral cephalometric radiographs were takenunder standardised conditions and scanned with anEpson Expression 1860 Pro scanner (Seiko EpsonCorporation, Nagano-ken, Japan) at a magnificationof 100 per cent. Quick Ceph 2000 (Quick CephSystems, San Diego, CA, USA) was used to measurethe overjet, overbite and inclinations of the upper andlower incisors (Figure 1).

The EMG records were obtained in the PhysiologyDepartment, Faculty of Medicine, Atatürk University.Before each recording session, the procedure wasexplained in detail to the subjects and their parents toallay anxiety. During the EMG recording, the sub-jects sat in an upright and relaxed position with theirhead in normal posture. Before placement of the surface electrodes, the recording sites on the upper lipwere thoroughly cleaned with 70 per cent alcohol to

minimise electrode impedance. Bipolar surface elec-trodes (EL350S, Biopac System, Inc, 42 AeroCamino, Galeta, CA, USA) were placed on eitherside of the philtrum.6 The electrodes consisted of twotin electrodes (9.5 mm diameter) embedded 30 mmapart in a watertight acrylic bar. Conductive paste(Sanborn Redux Electrode Paste, Hewlett PackardSunborn Division, Maltham, MA, USA) was appliedto the upper lip and at least 5 minutes elapsed for the paste to moisten the surface of the skin. EMGactivity in the upper lip muscle was recorded with thelips at rest, during maximal clenching, chewing oftwo hazelnuts and swallowing of the chewed nuts. Toobtain the rest position, each subject was asked toclose her/his eyes, moisten the lips, swallow, breathedeeply and relax their lower jaw. For maximal clench-ing the subjects were instructed to close their teeth incentric occlusion as forcibly as possible. The onlyinstruction given to the subjects for chewing andswallowing was to ask each subject to chew freely twohazelnuts and then to swallow the chewed nuts. A few trial tests were made to familiarise each subjectwith the procedures before beginning an EMGrecording.

Electromyographic records were taken at rate of 5000samples/second with maximum voltage of 10 mV.EMG signals were band-pass filtered (10 Hz – 1 kHz)using an A/D board (Biopac, MP100, Galeta, CA,USA) and stored as raw EMG recordings for off-lineanalysis with commercially-available software. RawEMGs were amplified, full-wave rectified, integrated,and analysed (Figure 2). For each procedure, the inte-grated EMG was analysed over 10 seconds. All pro-cedures were carried out with MP 100 data acquisi-tion and analysis systems (Biopac Systems EMG100

Figure 1. Cephalometric measurements.

Figure 2. Raw and integrated EMG obtained during chewing.

Overbite

U1_SN

IMPA

Overjet

amplifiers; MP100 module; AcqKnowledge MP 100Software version 3.0; Biopac System Inc., Galeta, CA,USA).

Amplitudes of action potentials were determined inmicrovolts (µV). The mean amplitude of the actionpotential for the rest position, and the peak-to-peakvalues of maximal clenching, chewing and swallowingwere used for the statistical analyses.

Statistical analysisThe gender differences in the chronological ages,cephalometric and electromyographic variables werecompared with Student’s t-test. Pearson’s correlationcoefficient was used to determine if there were signif-icant associations between the electromyographicvariables and the dental parameters. All statisticalanalyses were performed using the SPSS softwarepackage SPSS for Windows (Version 11.5, SPSS Inc,Chicago, IL, USA).

Results

There was no significant difference between the meanages of the boys and girls (p = 0.756). The ages of theboys ranged from 12.00 to 14.86 years (Mean age:13.47 years) and the ages of the girls ranged from11.08 to 15.00 years (Mean age: 13.56 years).

There were no significant gender differences in thecephalometric and electromyographic variables(Table I). Overjet in the girls was almost twice as variable as the overjet in the boys (Coefficients of variation: 73 per cent and 45 per cent, respective-ly), whereas the variability in swallowing and UI/SNwas almost identical in the boys and girls(Coefficients of variation, Swallowing: 35 per cent,34 per cent; UI/SN: 6.1 per cent, 5.9 per cent).Generally, the girls showed higher activity in all EMGparameters than the boys, but the EMG recordings inboth genders were very variable. For example, therange of EMG values in the boys and girls dur-ing chewing were 80 – 754 µV and 168 – 966 µV,respectively.

Associations between the cephalometric and electro-myographic variables are given in Table II. The posi-tive coefficients ranged from .005 (UI/SN and Rest)to .286 (UI/SN and Swallowing), and the negativecoefficients ranged from -.028 (Overjet and Rest) to-.228 (LI/MP and Rest). There was no statisticallysignificant correlation between the dental parametersand electromyographic activity in the superior orbic-ularis oris muscle. The only coefficient to approachstatistical significance occurred between swallowingand UI/SN (p = 0.062).

KILIC


Table I. Comparisons of the cephalometric and electromyographic variables in the boys and girls.

Mean SD Minimum Maximum p

Overjet (mm) Male 3.89 1.78 0.70 6.90 0.232Female 3.10 2.26 - 0.60 9.30

Overbite (mm) Male 0.92 1.14 -1.20 2.60 0.183Female 0.40 1.29 -1.90 4.00

U1/SN (degrees) Male 102.70 6.32 92.00 113.60 0.528Female 101.50 5.99 85.10 112.20

LI/MP (degrees) Male 90.26 4.66 83.70 96.90 0.204Female 88.21 5.39 75.90 97.70

Rest (µV) Male 33.74 13.08 15.35 60.50 0.132Female 40.84 15.85 15.20 77.57

Clenching (µV) Male 108.74 55.62 37.64 224.16 0.193Female 130.05 50.18 62.29 234.59

Chewing (µV) Male 326.88 188.59 80.14 754.89 0.527Female 359.32 150.28 168.37 966.50

Swallowing (µV) Male 432.22 151.85 174.62 737.48 0.718Female 415.87 141.97 207.74 718.71

ASSOCIATIONS BETWEEN UPPER LIP ACTIVITY AND INCISOR POSITIONS


Discussion

The present study failed to find significant associ-ations between the electromyographic activity insuperior orbicularis oris muscle at rest, during clench-ing, chewing and swallowing and the positions of theincisors. The associations were weak and no coeffi-cient exceeded .3. The highest statistical findingoccurred between UI/SN and swallowing, but thisaccounted for only 8 per cent of the variation andwhile this is unlikely to be of value clinically, it doesindicate the direction for future EMG studies. Thefindings on muscular activity in the upper lip duringchewing and swallowing agree with published workand, indirectly, support the view that the upper lipplays little part in determining the positions of theincisors, except in subjects with an anterior open bite.7

Although electromyography was introduced to theprofession 50 years ago, the method has delivered little of value to practicing orthodontists.8 Someproblems are the reliability and utility of recordingsmade with surface electrodes, the processing of the signal (raw versus integrated) and, in particular,the variability in recordings from the same musclesunder apparently identical conditions.9 The methodis primarily a research tool. Providing samples arewell-defined and the recording method carried outunder tightly controlled conditions by experiencedpeople, the findings can indicate directions for futureresearch.10 The finding that the coefficient betweenthe inclination of the upper central incisors and theactivity in the superior orbicularis oris muscle duringswallowing approached significance suggests that theupper lip and upper incisors need to be described ingreater detail.

One explanation for the negative findings may havebeen the choice of subjects: the majority had Class Imalocclusions. The upper lip in subjects with thismalocclusion acts as a passive ‘drape,’ covering theupper incisors at rest and during function and play-ing little/no part in forming an anterior oral seal. Insubjects with an increased overjet and incompetentlips and an anterior open bite, the upper lip may con-tribute to the formation of an anterior oral seal witha consequential increase in activity in the superiororbicularis oris muscle. This view is supported by pre-vious studies that have reported upper lip activity inchildren with atypical swallowing patterns andincompetent lips. The majority view, however, is thatthe upper lip plays little part in forming an anteriororal seal.

The computer software programme used to measurethe cephalometric radiographs had some advantagesover traditional tracings. It was possible to see thecontours of bony structures by enlarging the imageand changing the contrast when needed.11 The reproducibility of surface EMG recording by the MP 100 Data Acquisition and Analysis System hasbeen assessed previously and high interclass cor-relation coefficients for repeated trials were reported.12,13

Others have reported that activity in superior orbicu-laris oris muscle does not appear to be correlated withoverjet, overbite and incisor inclinations, even in sub-jects with Class II malocclusion.3,6 But in subjectswith atypical swallowing, the orbicularis oris musclein the upper lip is active, presumably because it par-ticipates with the tongue in forming an anterior oralseal.4 Significant correlations have, however, beenreported between inferior orbicularis oris muscleactivity and the positions of the incisors.2 Highamplitudes of activity in the lower lip were correlatedsignificantly with retroclined upper and lower incisors,but there was no significant association between theresting activity in the upper lip and the inclination of the lower incisors. Recent evidence suggests thatresting pressures from the lips and tongue are not balanced: lower lip pressure is less than tongue pres-sure in the mandibular incisor area, but upper lippressure is greater than tongue pressure in the maxil-lary incisor area.14 These unequal pressures may be balanced by metabolic activity in the periodontalligament.

Table II. Associations between the cephalometric and electromyograph-ic variables.

EMGparameters Overjet Overbite U1/SN L1/MP

Rest r -.028 -.117 .005 -.228p 0.855 0.438 0.972 0.128

Clenching r -.146 .040 .212 .010p 0.334 0.791 0.156 0.946

Chewing r .030 -.038 .204 -.119p 0.844 0.800 0.173 0.430

Swallowing r .022 -.160 .289 .033p 0.886 0.289 0.062 0.826

KILIC


Conclusion

The positions of the incisors do not appear to beinfluenced by muscle activity in the upper lip at rest,during clenching, chewing or swallowing.


Dr Nihat Kilic Atatürk Üniversitesi Dis Hekimligi FakültesiOrtodonti Anabilim Dalı 25240 ErzurumTurkeyTel: +90 442 2311810Fax: +90 442 2312270 – 2360945Email: [email protected] - [email protected]

References1. Thüer U, Ingervall B. Pressure from the lips on the teeth

and malocclusion. Am J Orthod Dentofacial Orthop 1986;90:234–42.

2. Lowe AA, Takada K. Associations between anterior tem-poral, masseter, and orbicularis oris muscle activity andcraniofacial morphology in children. Am J Orthod 1984;86:319–30.

3. Lowe AA. Correlations between orofacial muscle activityand craniofacial morphology in a sample of control andanterior open-bite subjects. Am J Orthod 1980;78:89–98.

4. Tosello DO, Vitti M, Berzin F. EMG activity of the orbi-cularis oris and mentalis muscles in children with malo-cclusion, incompetent lips and atypical swallowing: Part II.J Oral Rehabil 1999;26:644–9.

5. Jung MH, Yang WS, Nahm DS. Effects of upper lip closingforce on craniofacial structures. Am J Orthod DentofacialOrthop 2003;123:58–63.

6. Ahlgren JG, Ingervall BF, Thilander BL. Muscle activity innormal and postnormal occlusion. Am J Orthod 1973;64:445–56.

7. Proffit WR. Equilibrium theory revisited: factors influenc-ing position of the teeth. Angle Orthod 1978;48:175–86.

8. Moyers RE. Temporomandibular muscle contraction patterns in Angle Class II, Division 1 malocclusions: Anelectromyographic analysis. Am J Orthod 1949;35:837–57.

9. Cerere F, Ruf S, Pancherz H. Is quantitative electromy-ography reliable? J Orofac Pain 1996;10:38–47.

10. Schanne FJ, Chaffin DB. The effects of skin resistance andcapacitance coupling on EMG amplitude and power spectra.Electromyography 1970;10:273–86.

11. Cangialosi TJ, Chung JM, Elliott DF, Meistrell ME Jr.Reliability of computer-generated prediction tracing. AngleOrthod 1995;65:277–84.

12. Chien M, Wu Y, Chang Y. Assessment of diaphragm andexternal intercostals fatigue from surface EMG using cer-vical magnetic stimulation. Sensors 2008;8:2174–87.

13. Callaghan MJ. Electrical stimulation of the quadriceps muscle group in patients with patellofemoral pain syn-drome. (Thesis). Faculty of Medicine, Dentistry, Nursingand Pharmacy, University of Manchester, 2001, Manchester,UK.

14 Proffit WR. Biological basis of orthodontic therapy. In:Proffit WR, Fields HW, Sarver DM. ContemporaryOrthodontics. 4th ed. St Louis: Mosby Elsevier; 2007,pp.331–58.

Introduction

The curve of Spee (COS) describes the curved planeformed by the tips of the buccal cusps of themandibular dentition, and it is defined as the distancefrom the deepest point on the mandibular arch to theline connecting the tip of the mesio-buccal cusp ofthe lower second molar and the incisal edge of themost extruded incisor.1 This curve was first reportedto occur in the dentitions of mammals other thanman and was first applied to the human dentition byFerdinand Graf von Spee in 1890.2

The COS is flatter in deciduous dentitions than inadult dentitions and develops with the eruption ofthe mandibular first permanent molars and incisors.3,4

Once established it remains relatively stable.5,6

Differences in the times of eruption of the mandi-bular permanent teeth as well as variations in skeletalmorphology, sagittal jaw relationship and incisorocclusion may affect the depth of the COS.4,7,8

An increased curve of Spee before treatment has been associated with a low Frankfort-mandibularplane angle, deep overbite, increased overjet and Class


Effects of levelling of the curve of Spee on the proclination of mandibular incisors and expansionof dental arches: a prospective clinical trial

Nikolaos Pandis,* Argy Polychronopoulou,† Iosif Sifakakis,+ Margarita Makou+ andTheodore Eliades±

Private practice, Corfu,* Departments of Community and Preventive Dentistry† and Orthodontics,+ School of Dentistry, University of Athensand the Department of Orthodontics, School of Dentistry, Aristotle University of Thessaloniki,± Greece

Objectives: To investigate the effects of levelling the curve of Spee (COS) on the inclination of the mandibular incisors and thewidth of the mandibular arch. Methods: Fifty patients, 10–18 years of age, were selected using the following inclusion criteria: nonextraction treatment in themandibular arch; eruption of all mandibular teeth; no spaces in the mandibular arch; no crowding in the posterior mandibularsegments; a mandibular irregularity index greater than 2.5. The depth of the COS, the amount of crowding of the mandibularanterior dentition and the intercanine and intermolar widths were measured on standardised photographs of the casts. The inclinations of the mandibular incisors were measured on cephalometric radiographs. The paired t - test was used to analysechanges in the intercanine and intermolar widths and incisor inclinations before and after treatment, whilst the Wilcoxon signedranks test was used to examine changes in the COS with treatment. The data were further analysed with a regression analysisto determine the measurements that predicted a reduction of the curve of Spee at the 5 per cent level of significance.Results: The COS showed a median decrease of 0.9 mm, with 50 per cent of the cases ranging between 0.4 mm and 1.4mm. The sole predictor of curve flattening was the lower incisor to mandibular plane angle.Conclusions: The COS is mainly ‘flattened’ by proclining the mandibular incisors. For 1 mm of levelling the mandibular incisorswere proclined 4 degrees, without increasing arch width.(Aust Orthod J 2010; 26: 61–65)

Received for publication: August 2009Accepted: January 2010

Nikolaos Pandis: [email protected] Polychronolpoulou: [email protected] Sifakakis: [email protected] Makou: [email protected] Eliades: [email protected]

PANDIS ET AL


II molar malocclusion, but no significant gender differences have been identified.9

The rationale behind the traditional concept of level-ling the COS is somewhat obscure.10 It probablyfacilitated early attempts at deep overbite correctionbefore effective intrusion mechanics were available.10

Andrews believed that a deep COS may make italmost impossible to achieve a Class I canine rela-tionship and he associated the COS with post-treat-ment relapse. He concluded that flattening the COSshould be an orthodontic treatment goal, eventhough not all normal occlusions have flat occlusalplanes.11 A deep curve of Spee may also result inocclusal interferences during mandibular function.12

There are two types of COS: in the first one, which ismore common in cases requiring extractions, the pos-terior teeth are mesially inclined and they requirespace for uprighting.10 In the second type of COS, noadditional space is needed since the posterior axialinclinations are normal. In any case, levelling of thecurve of Spee by controlled incisor intrusion and/ormolar tip-back does not affect the amount of spacerequired.13,14 Some authors reported a linear relation-ship between the depth of the curve and the spacerequired for levelling,14-16 but others have concludedthat the relationship is nonlinear and that a numberof factors affect this relationship, including the site ofregistration of the arch circumference and the archform.17

An additional factor, which can affect both themandibular arch perimeter and arch space, is archexpansion. Steiner and Ricketts have proposed that

1 mm of lower incisor advancement produces 2 mmof arch length.18,19 Also, 1 mm of canine expansionproduces 1 mm of arch space, 1 mm of molar expan-sion results in only 0.25 mm increase in arch lengthand 2 mm per side of arch length is gained by molaruprighting.18 Germane et al.,20 used a mathematicalmodel to demonstrate that a 5 mm increase in archlength required approximately 5 mm of lateral expan-sion or 4 mm of incisor advancement. It was also discovered that wide dental arches produce more arch length per millimetre of expansion compared tonarrow arches.20

Currently, there is a lack of evidence of the extent ofproclination of mandibular incisors and the expan-sion of the mandibular dental arch associated withlevelling of the curve of Spee with a straight-wireappliance. Therefore, the objective of this prospectivestudy was to investigate the effects of levelling thecurve of Spee on the proclination of mandibular incisors and dental arch expansion.

Sample and methodsFifty patients, 10–18 years of age, were included inthis prospective study. The participants were selectedfrom a large pool of patients using the followinginclusion criteria: nonextraction treatment in themandible; eruption of all mandibular teeth; no spacesin the mandibular arch; no crowding in the posteriormandibular segments; a mandibular irregularityindex greater than 2.5. The basic demographic andclinical characteristics of the sample are shown inTable I. Table II depicts distribution of the patients ineach age group.

Table I. Demographic and clinical characteristics of the subjects.

Variable Mean ± SD(Per cent)

Age (years) 13.8 ± 1.3Gender Male 10 (20.0)

Female 40 (80.0)Total 50 (80.0)

Crowding (Irregularity index) 5.6 ± 2.3Crowding Moderate (<5.5 mm) 25 (50.0)

Severe (>5.5 mm) 25 (50.0)Angle Class I 30 (60.0)

II 18 (36.0)III 2 (4.0)

Mean treatment time 2.75 ± 0.84

Table II. Age distribution of the subjects.

Age N (Per cent)

10 1 (2)12 4 (8)13 18 (36)14 13 (26)15 10 (20)16 3 (6)18 1 (2)

All patients were bonded with a 0.022 inch slot edge-wise appliance and the lower arch was levelled using astraight-wire appliance. The wire sequence was as follows: 0.014 or 0.016 ideal form Sentalloy (GAC,Central Islip, NY, USA), followed by 0.020 inch idealform Sentalloy, 0.020 inch stainless steel wire and0.018 x 0.025 inch stainless steel wire. Brackets werebonded at a standard height on each tooth using abracket-positioning gauge (Ormco, Glendora, CA,USA).

Bracket bonding, archwire placement and all treat-ment stages were performed by the first author.Complete records were obtained before and at theend of treatment, and the amount of crowding of themandibular anterior teeth was assessed on dental castsusing the irregularity index, measured with a fine-tipdigital caliper, (Mitutoyo Digimatic NTD12-6” C,Mitutoyo Corporation, Japan). Changes in the inter-canine and intermolar widths were also measured onthe dental casts using the cusp tips of the lowercanines and the central grooves in the lower molars asreference points. The same archwire sequence wasused for all subjects, and all subjects were recalled at4–8 week intervals.

Pre- and post-treatment lateral cephalograms weretraced by the same person. The inclinations of themandibular incisors were assessed with the followingangular measurements: lower incisor to mandibularplane (L1-MP); lower incisor to N-B line (L1-NB);

and lower incisor to the A-Pog line (L1-APog). TheCOS was measured on standardised pre- and post-treatment photographs of the casts. Both sides of themodels were photographed (Figure 1). The resultantdigital images were entered into a cephalometric soft-ware programme (Viewbox 4.0, Dhal, Greece) andthe depth of the COS was measured using the secondmolars and incisors as reference points. The means ofthe right and left side measurements were used in allsubsequent calculations. The radiographs and themodels were measured in a random order to blind theinvestigator and reduce observer bias.

To assess the intra-examiner reliability, seven modelsand seven cephalometric radiographs were ran-domly selected from the records. The radiographswere re-traced and the measurements repeated.Additionally, the intercanine and intermolar widthswere remeasured on the casts. The reproducibility ofthe measurements was investigated with a paired t-test analysis for each variable. The analysis revealedno statistical significance between the first and secondmeasurements (p > 0.05).

Descriptive statistics for the study sample, clinicalcharacteristics, cast and cephalometric data were cal-culated. Paired t-tests were used to analyse changes inintercanine and intermolar widths and incisor incli-nations before and after treatment, and the Wilcoxonsigned rank test was used to compare the change inthe COS before and after treatment. A regressionanalysis determined the characteristics/measurementsthat could be used to predict a reduction in the COS.Incisor inclination, intercanine width, intermolarwidth and the clinical and demographic characteris-tics were used in a multiple median regression modeland non-significant variables were deleted by back-ward elimination (Deletion criterion, p > 0.05). A p < 0.05 was considered to be statistically significant.

CURVE OF SPEE AND MANDIBULAR INCISOR PROCLINATION


Table III. Cephalometric and cast characteristics at baseline and aftertreatment in all subjects (N = 50).

Measurement Baseline After treatment pMean ± SD Mean ± SD

Incisor inclinationL1-MP (degrees) 92.3 ± 6.8 96.8 ± 7.6 <10-3

L1-NB (degrees) 25.1 ± 5.9 29.8 ± 5.9 <10-3

L1-APog (degrees) 23.5 ± 4.6 28.8 ± 4.6 <10-3

Intercanine width (mm) 25.4 ± 1.8 27.1 ± 1.3 <10-3

Intermolar width (mm) 44.1 ± 2.6 45.8 ± 1.9 <10-3

Spee curve (mm) 2.0 ± 0.5 1.0 ± 0.4 <10-3+

L1-MP: Mandibular incisor to mandibular planeL1-NB: Mandibular incisor to nasion-point B lineL1-APog: Mandibular incisor to point A-pogonion linep value for comparison of baseline and post-treatment measurementsbased on paired t - test+p value for comparison of baseline and post-treatment measurementsbased on the Wilcoxon signed rank test

Figure 1. The depth of the COS was measured on digital images of the initial and final models.

PANDIS ET AL


All the analyses were conducted with the STATA 10.1statistical package (StataCorp LP, Houston, TX,USA).

Results

Table III gives the cephalometric and cast characteris-tics at baseline and after treatment in the subjects. Asshown, the inclinations of the incisors and the inter-canine and intermolar widths increased. The COSshowed a median decrease of 0.9 mm, with 50 percent of the cases ranging between 0.4 mm and 1.4mm and a slight expansion of the buccal segments(Mean value: 1.7 mm). On average, a 4 degree pro-clination of the mandibular incisors resulted in 1 mmlevelling in the COS. In the regression analysis onlythe baseline L1-MP angular measurement was foundto be a significant predictor of the COS levelling (p < 0.01). The data for this finding are not shown.

DiscussionLevelling of the COS is accomplished by molaruprighting, premolar eruption, incisor intrusion andincisor flaring or a combination of the above.21 Itseems that expansion may generate arch space incrowded arches, however, most levelling of the COSwith a straight-wire appliance was accomplished bythe extrusion of the premolars.22 In agreement with arecent study, which showed a marginally significantpost-treatment increase in the mandibular interca-nine width in Class II division 1 deep bite cases, wefound a small, but insignificant, increase in archwidth.23 The authors attributed their finding to normalphysiologic changes that occur with increasing age.23

We found that levelling of the COS with a straight-wire appliance correlated well with proclination ofthe mandibular incisors measured as an increase inthe mandibular incisor to MP line angle. Whilstother changes, such as an increase in both the inter-canine and intermolar widths, accompanied levellingof the curve, they were found to be coincidental andnot correlated with the actual levelling of themandibular arch.

Although many studies evaluating the amount ofspace required to correct 1 mm of the COS have indi-cated that the relationship is not one-to-one, someauthors have ignored their own evidence and pro-posed formulae to ‘accurately’ predict the spacerequired to level the COS.14-16 For example, Baldridgesuggested the following formula for the accurate pre-

diction of the required space Y = 0.488 X - .51, whereY = arch length differential in millimetres, X = sum ofright and left side maximum depths of the COS inmillimetres.15 Similar formulae have been developedby Garcia (Y = 0.657 X + 1.34) and Braun (Y = 0.2462X - 0.1723).14,16 On the other hand, Germaine et al.found that the relation between the levelling of theCOS and the space required did not follow a linearrelationship and it was dependent on arch form andthe depth of the COS.22 They also showed that undermost circumstances, less than 1 mm of space wasrequired to level 1 mm of Spee.17

In crowded mandibular arches with a deep COS, thespace required to level the curve should be consideredin the treatment planning and may indicate a needfor extractions. A case with 5 mm of crowding with aflat COS may be treated differently from a case withsimilar crowding, but with a 3 mm of COS, becauseproclination of mandibular incisors in the latter casecould predispose the incisors to periodontal compli-cations. In the opinion of one author the most effec-tive means of alleviating crowding is combined inci-sor proclination and canine expansion.20

There is no general agreement as to the most appro-priate biomechanical principles that should be usedto accomplish stable, long-term levelling of themandibular arch. There is no difference in the relapseof a corrected COS between extraction and non-extraction cases,21,24 although in 16 per cent of casesthe return of the COS was accompanied by anincrease in the overbite.21 Recent evidence sug-gests that the amount of relapse of the COS is notcorrelated with the initial depth of the curve.23,25

Relapse in the COS does not appear to be correlatedwith degree of the COS levelling during treatment.Some investigators consider that there is a higherincidence and magnitude of COS relapse if the COSis not completely reduced during treatment.23,26 Butthe evidence is by no means clear-cut: De Praeter et al. reported there was no such correlation betweenthe degree of levelling and relapse.25 There is alsosome evidence that the contrary may be true: themore the COS is levelled during treatment the moreit will relapse after treatment.21,22 The explanation ofthese conflicting results lies in the differences betweenthese studies, in particular the axial inclinations of theposterior teeth and the mechanisms of arch levelling.

Indiscriminate levelling in the mandibular arch canproduce undesirable side effects, including posterior

rotation of the mandible. Building in some occlusalcurvature could be desirable for both aesthetics andfunction.10 A recent study concluded that a curvedepth of 1.9 mm at the end of the treatment mightresult in higher stability, since these cases were assoc-iated with the least amount of post-treatmentchange.24 Moreover, uncontrolled arch levelling withcontinuous archwires containing a reverse COSshould be avoided, especially beyond the stage atwhich the occlusal plane is flat. After this stage, thesewires produce excessive incisor tipping resulting fromintrusive forces at the incisor brackets.14,27 Furtherinvestigation is required of COS levelling in differentfacial types and its effect on mandibular rotation.

Conclusion

Flattening of the COS is mostly achieved by pro-clination of the mandibular incisors. On average, a 4 degree proclination of the mandibular incisorsresults in 1 mm levelling of the COS. Only the L1-MP angular measurement was found to be a significant predictor of the COS levelling.


Dr Theodore Eliades 57 Agnoston Hiroon Str Nea Ionia GR-14231Greece Email: [email protected]

References 1. Hitchcock HP. The curve of Spee in Stone Age man. Am J

Orthod 1983;84:248–53.2. Spee FG. Die Verschiebungsbahn des Unterkiefers am

Schadel. Archives fur Anatomic und Physiologie. Leipzieg:Verlag Veitund Comp., 1890:285–93.

3. Ash MM. Wheeler’s dental anatomy, physiology and occlu-sion. Philadelphia: WB Saunders, 1993:151.

4. Marshall SD, Caspersen M, Hardinger RR, Franciscus RG,Aquilino SA, Southard TE. Development of the curve ofSpee. Am J Orthod Dentofacial Orthop 2008;134:344–52.

5. Carter GA, McNamara JA Jr. Longitudinal dental archchanges in adults. Am J Orthod Dentofacial Orthop 1998;114:88–99.

6. Bishara SE, Jakobsen JR, Treder JE, Stasi MJ. Changes in themaxillary and mandibular tooth size-arch length relation-shipfrom early adolescence to early adulthood. Am J OrthodDentofacial Orthop 1989;95:46–59.

7. Farella M, Michelotti A, van Eijden TMGJ, Martina R. Thecurve of Spee and craniofacial morphology: a multipleregression analysis. Eur J Oral Sci 2002;110:277–81.

8. Cheon SH, Park YH, Paik KS, Ahn SJ, Hayashi K,Yi WJ,Lee SP. Relationship between the curve of Spee and dento-facial morphology evaluated with a 3-dimensional recon-struction method in Korean adults. Am J Orthod DentofOrthop 2008;133:640.e7–14.

9. Xu H, Suzuki T, Muronoi M, Ooya K. An evaluation of thecurve of Spee in the maxilla and mandible of human per-manent healthy dentitions. J Prosthet Dent 2004;92:536–9.

10. Burstone JC, Marcotte MR. Problem solving in Orthodontics– Goal oriented treatment strategies. 1st edn. Chicago:Quintessence, 2000:40:181–3.

11. Andrews FL. The six keys to normal occlusion. Am J Orthod1972;62:296–309.

12. Dawson P. Evaluation, diagnosis and treatment of occlusalproblems. St. Louis: CV Mosby, 1974.

13. Woods M. A reassessment of space requirements for lowerarch leveling. J Clin Orthod 1986;20:770–8.

14. Braun S, Hnat WP, Johnson BE. The curve of Spee revisited.Am J Orthod Dentofacial Orthop 1996;110:206–10.

15. Baldridge DW. Leveling the curve of Spee: its effect onmandibular arch lengths. J Pract Orthod 1969;3:26–41.

16. Garcia R. Leveling the curve of Spee: a new prediction formula. J Charles H Tweed Int Found 1985;13:65–72.

17. Germane N, Staggers JA, Rubinstein L, Revere JT. Archlength considerations due to the curve of Spee: a mathemat-ical model. Am J Orthod Dentofacial Orthop 1992;102:251–5.

18. Ricketts R M, Bench RW, Gugino CF, Hilgers JJ, SchulhofRJ. Bioprogressive Therapy. Denver: Rocky Mountain/Orthodontics, 1979:115–6, 143–4.

19. Steiner CC. The use of cephalometrics as an aid to planningand assessing orthodontic treatment: Report of a case. Am JOrthod 1960;46:721–35.

20. Germane N, Lindauer SJ, Rubenstein LK, Revere JH,Isaacson RJ. Increase in arch perimeter due to orthodonticexpansion. Am J Orthod Dentofacial Orthop 1991;100:421–7.

21. Shannon KR, Nanda RS. Changes in the curve of Spee withtreatment and at 2 years posttreatment. Am J OrthodDentofacial Orthop 2004;125:589–96.

22. Bernstein RL, Preston CB, Lampasso J. Leveling the curve ofSpee with a continuous archwire technique: a long termcephalometric study. Am J Orthod Dentofacial Orthop2007;131:363–71.

23. Carcara S, Preston C B, Jureyda O. The relationshipbetween the curve of Spee, relapse, and the Alexander discipline. Semin Orthod 2001;7:90–9.

24. Lie F, Kuitert R, Zentner A. Post-treatment development ofthe curve of Spee. Eur J Orthod 2006;28:262–8.

25. De Praeter J, Dermaut L, Martens G, Kuijpers-Jagtman AM.Long-term stability of the leveling of the curve of Spee. AmJ Orthod Dentofacial Orthop 2002;121:266–72.

26. Preston CB, Maggard MB, Lampasso J, Chalabi O. Long-term effectiveness of the continuous and the sectional arch-wire techniques in leveling the curve of Spee. Am J OrthodDentofacial Orthop 2008;133:550–5.

27. Ferguson JW. Lower incisor torque-the effects of rectangulararchwires with a reverse curve of Spee. Br J Orthod 1990;17:311–15.

CURVE OF SPEE AND MANDIBULAR INCISOR PROCLINATION


Introduction

Obstructive sleep apnoea (OSA) is a chronic medicalcondition characterised by repetitive episodes ofupper airway collapse during sleep which results inapnoeic and hypopnoeic episodes, despite persistentthoracic and abdominal respiratory effort.1 OSA is asignificant and heavy burden on society, not only in afinancial sense, but also from the aspect of healthmorbidity. It is estimated that six per cent of theAustralian population (i.e. over 1.2 million people)experience sleep disorders, the most common ofwhich is OSA.2

Therapeutic options to manage this conditioninclude conservative measures, continuous positiveairway pressure (CPAP)3–5 and surgery.6 The conser-vative management of OSA includes the use of oral

appliances, the most common of which is themandibular advancement splint (MAS) that could beof one-piece design (monoblock) or of two pieces(duoblock).7 The one-piece design fixes the man-dible rigidly in a forward position, while a two-piece MAS allows some mandibular movement and thepossibility of further mandibular advancement.7,8

Previous studies have investigated the dental effects ofeither the monoblock or the duoblock systems.9–15

There has yet to be a comprehensive study comparingthe arch changes associated with both splints, whichmay influence the clinician’s decision when selectingan appropriate splint for the patient. We aimed toinvestigate the dental changes associated with the useof both splints and to compare the extent of changesbetween both systems.


A comparison of dental changes produced bymandibular advancement splints in the management of obstructive sleep apnoea

Hui Ching Ang and Craig DreyerSchool of Dentistry, The University of Adelaide, Adelaide, Australia

Background: Mandibular advancement splints (MAS) are a recognised and popular treatment option for obstructive sleepapnoea (OSA) due to their simplicity, tolerance and non-invasiveness.Objectives: To investigate and compare the dental changes associated with the use of monoblock and duoblock appliances.Methods: Fifty-two pretreatment and follow-up study models of patients from a public hospital and private dental clinic wereassessed. Seventeen subjects used a soft elastomeric monoblock appliance (MB), 29 subjects used a hard acrylic duoblock(DB) and six subjects wore a monoblock followed by a duoblock appliance (MB-DB). Measurements of dental and archchanges were obtained and analysed on study models and standardised bitewing radiographs.Results: A statistically significant reduction was observed in the maxillary intercanine distance in all splint categories, with DBusers showing the greatest decrease (p < 0.05). The change in the mandibular intercanine distances differed according tosplint categories (p < 0.05). MB and MB-DB patients demonstrated a decrease in this measurement variable, whereas anincrease was seen in DB users. A statistically significant increase in the mandibular intermolar distance was also observed in allsplint categories (p < 0.05), with DB users showing the greatest increase. Conclusions: Both MB and DB appliance systems produced similar, but mild dental effects. No particular appliance can be recommended and the choice of appliance should be considered on a case-by-case basis.(Aust Orthod J 2010; 26: 66–72)

Received for publication: June 2009Accepted: March 2010

Hui Ching Ang: [email protected] Dreyer: [email protected]

DENTAL CHANGES FROM MANDIBULAR ADVANCEMENT SPLINTS



The study was designed as a prospective, cross-sectional examination of study models of OSA sub-jects from an institution and a private dental clinic.The following inclusion criteria were applied:

1) Subjects with maxillary and mandibular first permanent molars and canines.

2) Subjects who had worn a MAS continuously (min-imum of five to six hours per night) for at least 6months.

Of the 191 subjects who fulfilled the inclusion cri-teria, only 52 (17 females, 35 males) attended forreview. Of these: 17 subjects (Mean age: 47 years;Range: 32 to 72 years) wore soft elastomeric mono-block appliances (Figure 1); 29 subjects (Mean age:

51 years; Range: 30 to 73 years) wore hard acrylicduoblock appliances (Figure 2); and six subjects(Mean age: 45 years; Range: 25 to 60 years) wore amonoblock followed by a duoblock appliance (MB-DB).

At recall, repeat study models were taken using algi-nate impression material and a bite registration wastaken with softened brown wax. Pretreatment andfollow-up study models were articulated in the inter-cuspal position on a Dentatus adjustable articulator.Measurements were made on the articulated studymodels using electronic digital calipers to 0.01 mm.

Vertical changes were measured directly on standard-ised bitewing radiographs using the digital calipers.Liquid barium was painted on the cusp tips of the

Figure 1. Monoblock appliance. Figure 2. Twinblock appliance.

Figure 3. Positioning of the modified Snapex film holder on the study model. Figure 4. Positioning the cone for a radiograph.

plaster first molars which produced a fine radiopaqueline to facilitate measurement. The bitewing filmswere held in position on the articulated models witha modified Snapex (Dentsply Pty Ltd., Mt. Waverley,Victoria, Australia) film holder. A customised flatmetal ruler was placed on the occlusal surface of themandibular first molars as a horizontal guide planefor the positioning the Snapex holder and radio-graphic machine cone (Figures 3 and 4). A metal wireattached to the Snapex holder, acted as a radiographichorizontal reference line (Figure 5).

Ten per cent (5 pretreatment, 5 follow-up) of themodels were remeasured and assessed using a paired t-test and Dahlberg statistics to determine the presenceof systematic and random errors.

The data were analysed using linear models and werefirst adjusted for a number of effects a priori, usingthe following models: variable prior to treatment =cast material + maxillary tooth number + mandibulartooth number + error; variable at the follow-up assessment (while still undergoing treatment) = castmaterial x operator + maxillary tooth number +mandibular tooth number. Appliance material andoperator were class variables and tooth number was acovariate. Subsequent analysis of predicted values wasthen undertaken using the fixed linear model: variable = gender + age + time + gender x time + agex time + splint x time + error. Gender and splint typewere class variables, age was a covariate, and treat-ment duration was a continuous measure of repeti-tion modelled using a spatial covariance structure(sp[pow]). Least squares variable estimates werederived for each gender by splint type combinationand plotted against the maximum duration of treat-ment to construct graphs illustrating the significantmodel effects.

Results

None of the paired t-tests comparing 10 per cent ofthe models with repeat measurements showed a sig-nificant difference (p > 0.05), indicating that therewere no systematic errors due to the equipment usedin the study. The random experimental error was lessthan 10 per cent of the observed population variationfor all measured variables, which suggested that themeasurement approach had little influence.

ANG AND DREYER


Figure 5. Example of radiographs taken to measure the posterior open bite. Figure 7. Mean value changes for the mandibular intercanine distance following treatment using the 3 MAS systems.MS1: Males using monoblock applianceMS2: Males using twinblock applianceMS3: Males using a monoblock followed by a twinblock applianceFS1: Females using monoblock applianceFS2: Females using twinblock applianceFS3: Females using a monoblock followed by a twinblock appliance

Figure 6. Mean value changes for the maxillary intercanine distance following treatment using the 3 MAS systems.MS1: Males using monoblock applianceMS2: Males using twinblock applianceMS3: Males using a monoblock followed by a twinblock applianceFS1: Females using monoblock applianceFS2: Females using twinblock applianceFS3: Females using a monoblock followed by a twinblock appliance

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Subjectively, subjects in general coped well with theirappliances and reported a reduction in sleep apnoeasymptoms. Repeat polysomnograph tests were con-ducted for most subjects and indicated successfulcontrol of OSA by the appliances.

Prior to treatment, a normal bilateral posterior over-bite was observed for all subjects. At recall, all subjectshad bilateral posterior open bites attributed to theappliances. Changes in the left side posterior openbite approached significance as treatment durationincreased (p = 0.05), while changes in the right posterior open bite were not statistically significant.

A significantly greater decrease in overjet wasobserved in MB and MB-DB subjects compared withthe DB subjects (p < 0.05). There was a tendency foranterior overbite to decrease with the length of timethe appliances were worn (p = 0.08). However, therewere no apparent statistically significant differencesbetween splint categories.

With treatment, a mesial shift of the mandibularcanine relative to the maxillary canine and first premolar was observed in all patients, resulting inbilateral changes to the canine relationships. Changesin the canine relationships on the left side were statis-tically significant (p < 0.05) for all splint categories.In comparison, changes to the right canine relation-ship were not statistically significant.

A mesial shift of the mandibular molar relative to themaxillary molar was also noted, causing a bilateralchange in the molar relationships. The shift was significantly different between splint categories (p < 0.05) for the left molar relationship, with MBand MB-DB users having greater change comparedwith DB users. In contrast, changes to the right molarrelationship were not statistically significant.

The maxillary intercanine distance decreased withappliance wear. The decrease was statistically signifi-cant between splint categories (p < 0.05), with DB

Table I. Study model measurements, expressed values are the follow-up minus the pretreatment measurements.

Variables Combined (N = 52) MB (N = 17) DB (N = 29) MB-DB (N = 6)Mean SD p Mean SD Mean SD Mean SD p

Maxillo-mandibular relationshipLeft posterior open bite (mm)a 1.4 0.9 0.05 1.4 1.0 1.4 0.8 1.9 1.0 0.24Right posterior open bite (mm)a 1.0 1.2 0.13 1.0 1.1 1.1 1.2 1.2 1.1 0.11Overbite (mm) -1.4 1.2 0.08 -1.3 1.2 0.3 0.5 -2.5 1.5 0.31Overjet (mm) -1.1 1.7 0.00 -0.9 1.4 -0.8 1.1 -2.2 1.3 0.03Left canine relationship (mm)b -1.1 1.5 0.03 -0.7 1.5 -1.1 1.3 -1.4 1.5 0.38Right canine relationship (mm)b -0.6 1.4 0.73 0.1 1.5 -1.1 1.0 -0.4 1.7 0.42Left molar relationship (mm)b -1.5 1.7 0.02 -1.5 1.6 -1.3 1.4 -1.5 2.2 0.00Right molar relationship (mm)b -1.3 1.8 0.30 -0.8 1.5 -1.2 1.3 -1.3 2.2 0.15

Maxillary archIntercanine distance (mm)c 0.0 0.4 0.52 0.2 0.5 -0.1 0.4 0.0 0.4 0.03Intermolar distance (mm)c 0.1 0.6 0.90 0.3 0.4 0.0 0.6 0.0 0.9 0.48Arch length (mm)c -1.3 2.0 0.26 -1.1 1.3 -0.8 1.8 -4.6 1.3 0.14Arch depth (mm)c 0.1 0.7 0.54 -0.1 0.7 0.3 0.8 -0.2 0.5 0.84

Mandibular archIntercanine distance (mm)c 0.1 0.6 0.44 0.0 0.4 0.0 0.7 0.3 0.5 0.00Intermolar distance (mm)c 0.3 0.9 0.17 0.1 0.5 0.3 1.1 0.9 0.3 0.01Arch length (mm)c 0.4 1.4 0.65 0.0 0.9 0.7 1.4 1.3 1.1 0.11Arch depth (mm)c -0.1 0.7 0.95 -0.2 0.9 -0.2 0.6 0.0 0.4 0.47

Significant values in bolda Means calculated from scores: overbite = -1, cusp-to-cusp relationship = 0, open bite = +1b Means calculated from scores: Class I = 0, Class II = +1, Class III = –1c Means calculated from scores: decrease = –1, no change = 0, increase = +1

users experiencing the greatest decrease (Figure 6). Incomparison, MB and MB-DB and users had lesschange.

Changes in the mandibular intercanine distance werestatistically significant between splint categories overtime (p < 0.05). MB and MB-DB users experienced areduction in mandibular intercanine distance, with agreater decrease apparent in MB users (Figure 7). Incontrast, mandibular intercanine distance remainedstable or increased slightly for all DB users.

The maxillary and mandibular intermolar distancesalso increased as treatment progressed. This changewas statistically significant between splint categories(p < 0.05) for the mandibular intermolar distance,with all DB patients experiencing the greatestincrease in comparison with MB and MB-DB users.In comparison, the increase in maxillary intermolardistance was not statistically significant betweensplint categories. A trend was observed such that theincrease in maxillary intermolar distance was greatestin DB subjects.

Discussion

Previous long-term cephalometric and study modelinvestigations have indicated that extended use ofMAS is associated with dentofacial changes.9,10,12,15,16

The orthodontic effects of the MAS observed inadults differ from functional appliances used in grow-ing children in which a dentoskeletal growth alter-ation is desired.9 While skeletal changes noted ofteninvolved a rotation and/or transposition of themandible,17–19 other studies have reported changes inoverbite and overjet, arch widths, and the canine andmolar relationships.9,10,15,16 However there has beenno comparative study which has examined the sideeffects of various MAS appliances. This may be impor-tant for the clinician when selecting an appropriateappliance for a patient. This study therefore aimed toinvestigate the dental changes associated with the useof MB and DB appliances and to compare the extentof the changes induced by both appliances.

MAS-induced posterior open bite is a variable that isnot commonly assessed in OSA studies. In the pres-ent study, standardised bitewing radiographs of thestudy models were taken, enabling the measurementof the posterior open bite. Barium liquid provided anexcellent radiopaque marker because it produced athin layer on study models from which accurate

measurements could be made. Anatomical anomalies,such as mandibular tori, which prevented optimalpositioning of the Snapex film holder were the samefor each patient. The potential radiographic magnifi-cation did not influence the difference (delta value)between the pretreatment and follow-up measure-ments and did not therefore affect statistical assessment of the variables.

A recent paper by Chen et al.20 used a 3-dimensionalcomputerised analysis system to accurately measureconventional variables such as overbite and overjet,and to enable the measurement of formerlyunassessed variables such as the posterior open bite.The reference points Chen and coworkers used tomeasure the posterior open bite were similar to thepoints we used.

The present study, as well as other studies,10,12,15

demonstrated bilateral changes to the canine andmolar relationships following MAS wear. However,changes in the left canine and molar relationshipswere statistically significant, while changes to theright side were not. Almeida and colleagues similarlyobserved a more significant mesial shift of the leftmandibular molar.21 These authors in their angledforce theory suggested that the right side of themandible was the preferred chewing side and this displaced the right condyle. Therefore, the result-ant force from the MAS on the teeth was directedanteriorly and to the left.

In contrast to the present study, Almeida and col-leagues reported a greater change in the right caninerelationship.21 This variation may be attributed todentoalveolar changes associated with longer dura-tions of treatment. The study by Almeida and associ-ates reported dentoalveolar changes following a meantreatment duration of 7.4 years. In comparison, thepresent study (mean of 3.6 years) suggested changesin the positioning of the mandible as the maxillaryand mandibular arch lengths remained stablethroughout treatment.

The decrease in the maxillary and mandibular inter-canine distances in the present study may possibly bedue to a change in the forces exerted by the intra-oraland extra-oral musculature. As the mandible is pos-tured forward during the day due to the nocturnally-induced mandibular advancement,19,21–23 a change intongue position9 occurs. This may cause an imbalanceof forces, leading to a greater influence of the extra-

ANG AND DREYER


oral facial musculature compared to intra-oral musculature (i.e. tongue) on the canines. Palatal orlingual movements of the canines follow, resulting inreductions in the maxillary and mandibular inter-canine distance.

Similarly, the force differential between the intra-oraland extra-oral musculature may also explain theincrease in the mandibular intermolar distance, possi-bly from buccal movement of the mandibular molars.This buccal movement may be further encourageddue to reduced occlusal contact between opposingmolars, which occurs as the posterior open bite devel-ops over time.9

A major difference between MB and DB applianceswas that the DB caused an overall increase inmandibular arch width (mandibular intercanine andintermolar distances),9,10 while the MB appliance wasassociated with a reduction in mandibular intercaninedistance, but an increase in mandibular intermolardistance.12,15 Even within the MB category, therewere statistically significant differences in themandibular intermolar distances between the hardacrylic and soft elastomeric appliances.12 The varia-tion in findings suggests that differences in appliancedesign may have an effect on the distribution offorces affecting the alignment of the teeth. The dis-parity in design and material of the MAS used in thecurrent study is possibly an important factor, whichmay account for the differences in mandibular archwidth changes. The MB appliance in the currentstudy was made of soft elastomeric material with agreater alveolar coverage, while the hard acrylic DBdid not have any alveolar coverage. Alveolar coveragehas been suggested to affect the force vectors on thedental arches.12 The type of occlusal splint materialused has been shown to affect the nocturnal activityof the masticatory muscles; muscle activity isdecreased in 80 per cent of hard splint users, butincreased in 50 per cent of those using soft splints.24

It is possible that the hard DB and soft MB appli-ances, also used nocturnally in the present study, maylead to similar patterns in masticatory muscle activi-ty. It is unclear how masticatory muscle activity mayaffect the mandibular arch width and this would benefit from further investigation.

There were limitations associated with the studywhich require future consideration. Because there wasno objective measure of appliance wear, the patients’

reporting of wear was relied upon. In addition,because of the long time scale (43 to 414 weeks), itwas not possible to split the samples into two or threetime groups for comparison. Doing so would haverendered group numbers too small for informativestatistical assessment. Furthermore, it was difficult toperform any meaningful comparisons of mandibularadvancement because data were not available for allsubjects, and, had the combined MB-DB group beenremoved from the sample, it would have resulted in areduction in statistical power. Future investigationsshould ideally include cephalometric measurementsin conjunction with study model assessments to pro-vide a better understanding of the dental changesassociated with MAS.

Conclusions

A comparison of dental changes produced by the MBand DB appliance systems is important to aid the clinician in selecting an effective device that has min-imal dental side effects. The present study indicatedseveral statistically significant observations, includingchanges in the intercanine and intermolar distanceswhich may possibly be explained by a daytime imbal-ance of forces between the intra-oral and extra-oralmusculature due to nocturnally-induced mandibularadvancement. A major difference between MB andDB appliances was that the DB caused an overallincrease in mandibular intercanine and intermolardistances,9,10 while the MB appliance was associatedwith a reduction in mandibular intercanine distance,but an increase in mandibular intermolar distance.12,15

The variation in findings suggests that differences inappliance design (splint material, alveolar coverage)may have an effect on the distribution of forces affecting the alignment of the teeth.

While some of the orthodontic measurementsdemonstrated trends towards differences between themonoblock and duoblock systems, these were not sig-nificantly different. This indicates that both appliancesmay be used safely as they both produced similar, butmild, effects, and no particular recommendation canbe made regarding the choice of appliance.

Acknowledgments

The authors would like to thank Dr Norm Vowles forassisting with the data collection, and Dr TobyHughes for his help with the statistical analysis.



ANG AND DREYER



Dr Craig DreyerSchool of DentistryThe University of AdelaideAdelaide SA 5005AustraliaTel: (+61 8) 8303 3299Fax: (+61 8) 8303 3444Email: [email protected]

References 1. Young T, Peppard PE, Gottlieb DJ. Epidemiology of

obstructive sleep apnea: a population health perspective. AmJ Respir Crit Care Med 2002;165:1217–39.

2. Access Economics. Wake up Australia: The Value of HealthySleep: Sleep Health Australia; 2004:1–17.

3. Morgenthaler TI, Kapen S, Lee-Chiong T, Alessi C,Boehlecke B, Brown T et al. Practice parameters for themedical therapy of obstructive sleep apnea. Sleep 2006;29:1031–5.

4. Taasan VC, Block AJ, Boysen PG, Wynne JW. Alcoholincreases sleep apnea and oxygen desaturation in asympto-matic men. Am J Med 1981;71:240–5.

5. Kushida CA, Littner MR, Hirshkowitz M, Morgenthaler TI,Alessi CA, Bailey D et al. Practice parameters for the use ofcontinuous and bilevel positive airway pressure devices totreat adult patients with sleep-related breathing disorders.Sleep 2006;29:375–80.

6. Won CH, Li KK, Guilleminault C. Surgical treatment ofobstructive sleep apnea: upper airway and maxilloman-dibular surgery. Proc Am Thorac Soc 2008;5:193–9.

7. Hoffstein V. Review of oral appliances for treatment ofsleep-disordered breathing. Sleep Breath 2007;11:1–22.

8. Hoekema A, Stegenga B, De Bont LG. Efficacy and co-morbidity of oral appliances in the treatment of obstructivesleep apnea-hypopnea: a systematic review. Crit Rev OralBiol Med 2004;15:137–55.

9. Almeida FR, Lowe AA, Otsuka R, Fastlicht S, Farbood M,Tsuiki S. Long-term sequellae of oral appliance therapy inobstructive sleep apnea patients: Part 2. Study-model analysis.Am J Orthod Dentofacial Orthop 2006;129:205–13.

10. Chen H, Lowe AA, de Almeida FR, Fleetham JA, Wang B.Three-dimensional computer-assisted study model analysisof long-term oral-appliance wear. Part 2. Side effects of oralappliances in obstructive sleep apnea patients. Am J OrthodDentofacial Orthop 2008;134:408–17.

11. Hammond RJ, Gotsopoulos H, Shen G, Petocz P, CistulliPA, Darendeliler MA. A follow-up study of dental and skele-tal changes associated with mandibular advancement splintuse in obstructive sleep apnea. Am J Orthod DentofacialOrthop 2007;132:806–14.

12. Marklund M, Franklin KA, Persson M. Orthodontic side-effects of mandibular advancement devices during treatmentof snoring and sleep apnoea. Eur J Orthod 2001;23:135–44.

13. Pitsis AJ, Darendeliler MA, Gotsopoulos H, Petocz P,Cistulli PA. Effect of vertical dimension on efficacy of oralappliance therapy in obstructive sleep apnea. Am J RespirCrit Care Med 2002;166:860–4.

14. Robertson C, Herbison P, Harkness M. Dental and occlusalchanges during mandibular advancement splint therapy insleep disordered patients. Eur J Orthod 2003;25:371–6.

15. Rose EC, Staats R, Virchow C, Jr., Jonas IE. Occlusal andskeletal effects of an oral appliance in the treatment ofobstructive sleep apnea. Chest 2002;122:871–7.

16. Marklund M. Predictors of long-term orthodontic sideeffects from mandibular advancement devices in patientswith snoring and obstructive sleep apnea. Am J OrthodDentofacial Orthop 2006;129:214–21.

17. Bondemark L. Does 2 years’ nocturnal treatment with amandibular advancement splint in adult patients with snor-ing and OSAS cause a change in the posture of themandible? Am J Orthod Dentofacial Orthop 1999;116:621–8.

18. Fransson AM, Tegelberg A, Svenson BA, Lennartsson B,Isacsson G. Influence of mandibular protruding device onairway passages and dentofacial characteristics in obstructivesleep apnea and snoring. Am J Orthod Dentofacial Orthop2002;122:371–9.

19. Ringqvist M, Walker-Engstrom ML, Tegelberg A, RingqvistI. Dental and skeletal changes after 4 years of obstructivesleep apnea treatment with a mandibular advancementdevice: a prospective, randomized study. Am J OrthodDentofacial Orthop 2003;124:53–60.

20. Chen H, Lowe AA, de Almeida FR, Wong M, Fleetham JA,Wang B. Three-dimensional computer-assisted study modelanalysis of long-term oral-appliance wear. Part 1:Methodology. Am J Orthod Dentofacial Orthop 2008;134:393–407.

21. Almeida FR, Lowe AA, Sung JO, Tsuiki S, Otsuka R. Long-term sequellae of oral appliance therapy in obstructive sleepapnea patients: Part 1. Cephalometric analysis. Am J OrthodDentofacial Orthop 2006;129:195–204.

22. Fritsch KM, Iseli A, Russi EW, Bloch KE. Side effects ofmandibular advancement devices for sleep apnea treatment.Am J Respir Crit Care Med 2001;164:813–8.

23. Robertson CJ. Dental and skeletal changes associated withlong-term mandibular advancement. Sleep 2001;24:531–7.

24. Okeson JP. The effects of hard and soft occlusal splints onnocturnal bruxism. J Am Dent Assoc 1987;114:788–91.

Introduction

Ozone water, which contains three times more oxygen than tap water, has been used to disinfect thewater systems in dental units.1–3 Ozone is thought topenetrate the cell and oxidise intracellular amino andnucleic acids.2 Cellular lysis depends to some extenton the severity of these reactions.4,5 The polymerisa-tion and bond strengths of orthodontic adhesivesused on teeth washed with ozone water may be affectedby the high concentration of oxygen. We aim todetermine if post-prophylaxis washing of bovineenamel with ozone water affects the bond strengthsand sites of failure of orthodontic brackets bondedwith different adhesives systems.

Materials and methodsOzone waterThe materials used to produce ozone water were: anoxygen cylinder with reduction valves and mano-

meters; an ozone generator (Ozone, mod. EAS 30 -UV) with a production capacity of 0.5 g/h (0.25 percent, p/p, in the mixture of oxygen and ozone); acrystal reactor with a capacity of 100 ml, coupled tothe ozone generator. To produce ozone water, a mix-ture of oxygen and ozone were bubbled through 100ml of distilled water during autoclaving in the crystal reactor. To ensure sterilisation and cleaning of the system, ozone was bubbled through 100 ml of auto-claved distilled water, contained in the crystal reactor,for 20 minutes. This water was discarded andreplaced with an equal volume of water to start theexperiment. The ozone concentration in the waterused was 0.6 mg/L.

Preparation of the teethOne hundred and twenty extracted, bovine perman-ent mandibular incisors were collected and cleaned.They were then placed in 10 per cent formaldehyde


Does ozone water affect the bond strengths oforthodontic brackets?

Matheus Melo Pithon and Rogerio Lacerda dos Santos Faculty of Dentistry, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil

Background: Ozone water can be used to eliminate micro-organisms from the water systems in dental offices.Objectives: To determine if ozone water diminishes the bond strength of orthodontic adhesives.Methods: One hundred and twenty bovine mandibular incisors were randomly divided into four equal groups. The teeth werecleaned with pumice and washed either with tap water (Groups 1 and 3) or with ozone water Groups (2 and 4) before bonding stainless steel orthodontics brackets to the teeth with either a composite resin (Groups 1 and 2; Transbond XT, 3MUnitek, Monrovia, CA, USA) or a resin-modified glass ionomer cement (Groups 3 and 4; Fuji Ortho LC, GC AmericaCorporation, Tokyo, Japan). The manufacturers’ recommendations for bonding were followed. All samples were subjected tothermal cycling and the shear bond strengths were determined with a universal testing machine. The Adhesive Remnant Index(ARI) was used to score the amount of resin remaining on the teeth after debonding the brackets.Results: There were no statistical differences in the shear bond strengths of the brackets debonded from enamel washed witheither ozone water or tap water or between the groups bonded with the two adhesive resins (p = 0.595). The ARIs in Groups2 and 3 were significantly different from the ARIs in Groups 3 and 4 (p = 0.030).Conclusion: Ozone water did not alter the bond strength of brackets bonded with composite resins, but it did alter the sites ofresin fracture when Fuji Ortho LC was used.(Aust Orthod J 2010; 26: 73–77)

Received for publication: August 2009Accepted: February 2010

Matheus Pithon: [email protected] Lacerda dos Santos: [email protected]

PITHON AND SANTOS


solution and stored in a refrigerator (8 °C) untilrequired. Only caries-free teeth with intact buccalenamel, no previous chemical treatment (e.g. hydro-gen peroxide) and no enamel cracks caused by theextraction forceps were used.

The teeth were embedded in PVC reducing bushes(Tigre, Joinville, Brazil) with acrylic resin (Clássico,São Paulo, Brazil), leaving only the crowns exposed.To faciliate mechanical testing, the buccal surfaces ofthe crowns were placed perpendicular to the shearingbase of the dies. The embedded teeth were placed indistilled water and stored in a refrigerator (8 °C) untilrequired for testing.

The mounted teeth were randomly divided into fourequal groups. The buccal surfaces of the teeth werecleaned for 15 seconds with a paste made from extra-fine pumice (S.S. White, Juiz de Fora, Brazil) mixedwith either tap water (Groups 1 and 3) or ozone water(Groups 2 and 4) and rubber prophylaxis cups(Viking, KG Sorensen, Barueri, Brazil). The teethwere then rinsed with an air - tap water spray (Groups1 and 3) or an ozone water spray (Groups 2 and 4) for15 seconds and dried with oil-free air for 15 seconds.The rubber cups were replaced after they had beenused on five teeth in the same group.

Stainless steel 0.018 inch upper central incisor brackets (Morelli, Sorocaba, Brazil), with a mean basearea of 14.2 mm2, were bonded to the teeth inGroups 1 and 2 with Transbond XT (3M Unitek,Monrovia, CA, USA) and to the teeth in Groups 3and 4 with Fuji Ortho LC (GC AmericaCorporation, Tokyo, Japan). The resin was applied toeach bracket base and the bracket seated on the toothwith 300 g force using a Correx gauge for 10 seconds.The force was applied uniformly to ensure an even

adhesive thickness between bracket and enamel, andthe adhesive flash was removed with a dental probe.A Light Curing Unit 2500 (3M Dental Products,Oakdale, CA, USA) with an intensity of 550mW/cm2 was applied at a distance of 1 mm to each side of the bracket for 10 seconds (Total curingtime: 40 seconds). The light intensity was calibratedfor each bracket using a radiometer (Demetron,Danburry, CT, USA).

The bonded teeth were left undisturbed for 30 minutes to ensure complete polymerisation of theadhesive. After a 24-hour period of immersion in distilled water the specimens were alternately cycled(500 cycles) through distilled water baths at 5 °C and 55 °C, with a dwell time of 15 seconds in eachbath.6

Mechanical testing and statistical analysesA purpose-built device was used to stabilise the speci-mens during mechanical testing. The brackets weredebonded with an Emic DL 10.000 universal testingmachine (São José dos Pinhais, Paraná, Brazil) at acrosshead speed of 0.5 mm/minute. A shear load wasapplied to the bracket base with a chisel-shaped rodand the force required to dislodge the bracket record-ed. The shear bond strength (SBS) in megapascals(MPa) was calculated from this data. Followingdebonding the enamel surfaces were examined with astereomicroscope (Stemi 2000-C; Carl Zeiss,Göttingen, Germany) at x16 magnification and theadhesive remnant index (ARI) recorded. With the lat-ter index: 0, no adhesive left on the tooth; 1, less thanhalf the adhesive left on the tooth; 2, more than halfthe adhesive left on the tooth; 3, all of the adhesiveleft on the tooth.

Table I. Comparisons of shear bond strength, in megapascals.

Group Mean SD Minimum Median Maximum ANOVA

1 21.02 2.41 17.27 22.07 24.24 A2 20.07 1.94 16.70 20.21 23.1 A3 19.81 2.34 16.23 20.06 22.9 A4 19.44 1.87 17.23 18.73 23.2 A

Group 1: Transbond XT/tap water; Group 2: Transbond XT/ozonewater; Group 3: Fuji Ortho LC/tap water; Group 4: Fuji OrthoLC/ozone waterGroups with the same letter were not significantly different from eachother, p > 0.05

Table II. ARI scores.

Group ARI score*

0 1 2 3

1 3 3 15 92 9 6 12 33 0 3 15 124 0 12 18 0

* 0, no adhesive remaining on the tooth; 1, less than half of adhesiveremaining on the tooth; 2, more than half of the adhesive remaining onthe tooth; 3, all adhesive remaining on the teeth

Statistical analyses were performed using theStatistical Package for the Social Sciences version 13.0(SPSS Inc, Chicago, IL, USA). An analysis of vari-ance (ANOVA) was used to determine whether therewere significant differences among the groups and theTukey HSD test was applied post-hoc if necessary.The Kruskal-Wallis and Mann-Whitney U tests wereused to compare the ARI scores.

Results

The results are given in Tables I to III and Figure 1.The SBS of the brackets washed with ozone water(Groups 2 and 4) were slightly less than the bracketswashed with tap water (Groups 1 and 3), but the differences were not statistically significant.

There were, however, statistically significant differ-ences in the ARI between Groups 2 and 3 andGroups 3 and 4 (Tables II and III).

Discussion

Contamination of piped water supplies with micro-organisms poses a health danger to patients. Ozone,which has an antimicrobial action, is used to preventthe formation of biofilms in water pipes and to disin-fect water distribution systems in dental offices.4,7–10

Although ozone water is widely used, little is knownof its effects on the polymerisation processes of adhesive and restorative materials. We postulated thatthe additional oxygen molecules in ozone water,which contains three times more oxygen than tapwater, may hamper the polymerisation processes inorthodontic adhesive materials and affect the shearbond strengths and sites of fracture of the materi-als.11–21 We found no statistically significant differ-ences in the shear bond strengths of resins whenozone water was used to wash the enamel prior tobonding, but the sites of resin fracture duringdebonding were affected. Used in this limited way, we

concluded that ozone water did not affect the bondstrengths of brackets bonded with Transbond XT andFuji Ortho LC composite resins.

The materials we evaluated (Transbond XT and FujiOrtho LC) are widely used in the clinic and in shearbond strength studies.22–25 Although we found nostatistically significant differences between the SBSs ofthe materials, the mean SBS of the brackets bondedwith Transbond XT were slightly higher and morevariable than the brackets in comparable groupsbonded with Fuji Ortho LC resin. The mean shearbond strengths we found agree with previous studiesthat have used Transbond XT and Fuji Ortho LC,23,24

and fell within the range of values (5–20 Mpa)considered by Owens26 to be suitable for clinical use.

Lower mean ARI values, indicating that less adhesiveremained on the teeth after debonding, were found inthe groups washed with ozone water (Groups 2 and 4)than those washed with tap water (Groups 1 and 3).These differences were significant between Groups 2(Transbond XT/ozone water) and 3 (Fuji OrthoLC/tap water) and between Groups 3 (Fuji OrthoLC/tap water) and 4 (Fuji Ortho LC/ozone water).These results are clinically important, since with aslight reduction in ARI promoted by the ozone water,the enamel surface is less protected during the bracket removal process, and fractures of the enamelare more likely to occur.

DOES OZONE WATER AFFECT THE BOND STRENGTHS OF ORTHODONTIC BRACKETS


Table III. Group comparisons of the ARI, probability values.

Groups 1 2 3 4

1 0.128 0.508 0.1552 0.030 0.5113 0.0244


1 2 3 4Groups

She

ar b

ond

str

engt

h (M

pa)

26.00

24.00

22.00

20.00

18.00

16.00

Figure 1. Box plots of shear bond strength values.

PITHON AND SANTOS


We also found a reduction in the mean ARI betweenthe teeth bleached with different concentrations ofhydrogen peroxide, although there was no statisticaldifference between the bond strengths.27 In the pres-ent study with ozone water, the differences in ARIcan be attributed to the presence of oxygen moleculesin the bond area. It is worth pointing out that theconcentration of ozone in the water we used was 0.6mg/L, the same concentration was used by Velano,28

in her study of the micro-biocidal action of ozonewater. This concentration appears to be ideally suitedto disinfect dental water systems and prevent the for-mation of biofilms.

Conclusion

The hypothesis that ozone water would interfere inthe shear bond strength of orthodontic brackets wasnot proved. Washing the enamel with ozone waterbefore orthodontic bracket bonding did not diminishthe shear bond strength, but it did alter the sites ofresin fracture when Fuji Ortho LC was used.


Dr Matheus Melo PithonAv. Otávio Santos395, sala 705Centro OdontomédicoDr. Altamirando da Costa LimaVitória da ConquistaBahiaBrazil CEP 45020750Email: [email protected]

References1. Edmunds LM, Rawlinson A. The effect of cleaning on blood

contamination in the dental surgery following periodontalprocedures. Aust Dent J 1998;43:349–53.

2. Huntington MK, Williams JF, Mackenzie CD. Endotoxincontamination in the dental surgery. J Med Microbiol 2007;56:1230–4.

3. Putnins EE, Di Giovanni D, Bhullar AS. Dental unit water-line contamination and its possible implications during periodontal surgery. J Periodontol 2001;72:393–400.

4. Acosta–Gio AE, Borges–Yanez SA, Flores M, Herrera A,Jeronimo J, Martinez M et al. Infection control attitudesand perceptions among dental students in Latin America:implications for dental education. Int Dent J 2008;58:187–93.

5. Askarian M, Assadian O. Infection control practices amongdental professionals in Shiraz Dentistry School, Iran. ArchIran Med 2009;12:48–51.

6. Thomas MV, Jarboe G, Frazer RQ. Infection control in thedental office. Dent Clin North Am 2008;52:609–628, x.

7. Zimmerli M, Widmer AF, Dangel M, Filippi A, Frei R,Meyer J. Methicillin–resistant Staphylococcus aureus(MRSA) among dental patients: a problem for infectioncontrol in dentistry? Clin Oral Investig 2008.

8. Loncar B, Stipetic MM, Matosevic D, Tarle Z. Ozone application in dentistry. Arch Med Res 2009;40:136–7.

9. Nogales CG, Ferrari PH, Kantorovich EO, Lage–MarquesJL. Ozone therapy in medicine and dentistry. J ContempDent Pract 2008;9:75–84.

10. Wilson SR, Solomon KR, Tang X. Changes in troposphericcomposition and air quality due to stratospheric ozonedepletion and climate change. Photochem Photobiol Sci2007;6:301–10.

11. Nagayoshi M, Kitamura C, Fukuizumi T, Nishihara T,Terashita M. Antimicrobial effect of ozonated water on bacteria invading dentinal tubules. J Endod 2004;30:778–81.

12. Pereira JT, Costa AO, de Oliveira Silva MB, Schuchard W,Osaki SC, de Castro EA et al. Comparing the efficacy ofchlorine, chlorine dioxide, and ozone in the inactivation ofCryptosporidium parvum in water from Parana State,Southern Brazil. Appl Biochem Biotechnol 2008;151:464–73.

13. Uhm HS, Hong YF, Lee HY, Park YH. Increase in the ozonedecay time in acidic ozone water and its effects on steriliz-ation of biological warfare agents. J Hazard Mater 2009;168:1595–601.

14. Zuma F, Lin J, Jonnalagadda SB. Ozone–initiated disinfec-tion kinetics of Escherichia coli in water. J Environ SciHealth A Tox Hazard Subst Environ Eng 2009;44:48–56.

15. Azarpazhooh A, Limeback H. The application of ozone indentistry: a systematic review of literature. J Dent 2008;36:104–16.

16. King MD, Thompson KC, Ward AD, Pfrang C, Hughes BR.Oxidation of biogenic and water–soluble compounds inaqueous and organic aerosol droplets by ozone: a kinetic andproduct analysis approach using laser Raman tweezers.Faraday Discuss 2008;137:173–192; discussion 193–204.

17. Lazzarotto B, Frioud M, Larcheveque G, Mitev V, Quaglia P,Simeonov V et al. Ozone and water–vapor measurements byRaman lidar in the planetary boundary layer: error sourcesand field measurements. Appl Opt 2001;40:2985–97.

18. Amra I, Samsodien G, Shaikh A, Lalloo R. Xeno IIIself–etching adhesive in orthodontic bonding: the next generation. Am J Orthod Dentofacial Orthop 2007;131:160e111–115.

19. Årtun J, Bergland S. Clinical trials with crystal growth conditioning as an alternative to acid–etch enamel pretreatment. Am J Orthod 1984;85:333–40.

20. Coleman DC, O’Donnell MJ, Shore AC, Russell RJ. Biofilmproblems in dental unit water systems and its practical control. J Appl Microbiol 2009;106:1424–37.

21. Johansson E, Andersson–Wenckert I, Hagenbjork–Gustafsson A, Van Dijken JW. Ozone air levels adjacent to adental ozone gas delivery system. Acta Odontol Scand 2007;65:324–30.

22. Cacciafesta V, Sfondrini MF, Stifanelli P, Scribante A, KlersyC. The effect of bleaching on shear bond strength of brackets bonded with a resin–modified glass ionomer. Am JOrthod Dentofacial Orthop 2006;130:83–7.

23. Pithon MM, de Oliveira Ruellas AC, Sant’Anna EF, deOliveira MV, Alves Bernardes LA. Shear bond strength ofbrackets bonded to enamel with a self–etching primer.Effects of increasing storage time after activation. AngleOrthod 2009;79:133–7.

24. Pithon MM, Dos Santos RL, de Oliveira MV, Ruellas AC,Romano FL. Metallic brackets bonded with resin–reinforcedglass ionomer cements under different enamel conditions.Angle Orthod 2006;76:700–4.

25 Pithon MM, Oliveira MV, Ruellas AC, Bolognese AM,Romano FL. Shear bond strength of orthodontic brackets toenamel under different surface treatment conditions. J ApplOral Sci 2007;15:127–30.

26. Owens SE, Miller BH. A comparison of shear bondstrengths of three visible light–cured orthodontic adhesives.Angle Orthod 2000;70:352–6.

27. Pithon MM, Ruellas AC, Sant’Anna EF. Effect of bleachingwith hydrogen peroxide into different concentrations onshear strength of brackets bonded with a resin–modifiedglass ionomer. Braz J Oral Sci 2008;7:1484–8.

28. Velano HE, do Nascimento LC, de Barros LM, Panzeri H. Invitro assessment of antibacterial activity of ozonized wateragainst Staphylococcus aureus. Pesqui Odontol Bras2001;15: 18–22.

DOES OZONE WATER AFFECT THE BOND STRENGTHS OF ORTHODONTIC BRACKETS


Introduction

Skeletal Class III malocclusion is considered one ofthe most complex and difficult orthodontic problemsto treat. Much controversy and uncertainty surroundsthe efficacy and stability of early treatment of thiscondition.1–3 Since 45 to 65 per cent of skeletal ClassIII malocclusions have maxillary retrusion and a nor-mal or prognathic mandible, many Class III patientscan be managed with maxillary expansion and face-mask therapy.4,5 Although this approach has beendescribed as maxillary protraction, the anteroposter-ior discrepancy is corrected by a combination ofskeletal and dental movements in the maxilla andmandible.2,6–13

Recent publications have reported that favourableoutcomes can be maintained long-term in approxi-mately 65 to 75 per cent of cases treated with thistype of early orthopaedic Class III treatment.14–18

However, a recent finite element study by Holberg,

Mahaini and Rudzki19 has cast doubt on the notionof remodelling changes in the facial skeleton. Theyreported that the strains applied by a facemask werenot high enough to stimulate bone growth in the circum-maxillary sutures. Their findings lead us toformulate a study to investigate the skeletal, dento-alveolar and soft tissue effects of combined facemask,intermaxillary traction and rapid maxillary expansiontherapy in young subjects with skeletal Class III mal-occlusion. We postulated that it would be possible tomaximise the skeletal changes and minimise the dento-alveolar changes by starting treatment in the latedeciduous to mixed dentition. We also aimed todetermine the changes at short intervals throughouttreatment.


The sample comprised 15 children (8 girls, 7 boys)between 5 years, 1 month and 11 years, 2 months of


Incremental effects of facemask therapy associatedwith intermaxillary mechanics

Guilherme Thiesen,* Juliana de Oliveira da Luz Fontes,† Michella Dinah Zastrow+

and Naudy Brodbeck May*

Departments of Orthodontics* and Radiology,+ School of Dentistry, University of South Santa Catarina and Private Practice,† Florianópolis,Santa Catarina, Brazil

Objectives: To determine the dentofacial changes in children with skeletal Class III malocclusions treated with maxillary expansion, external maxillary protraction and intermaxillary traction.Methods: Fifteen Class III patients in either the deciduous or the mixed dentition (Mean age: 7.6 years; SD: 1.9 years) wereused. The children were treated with a modified Haas expander, a modified lingual arch, intermaxillary elastics and facemaskfor nine months. Lateral cephalometric radiographs were taken at the beginning of treatment (T1) and at 3-month intervals (T2,T3, T4). Results: Most significant sagittal skeletal modifications occurred in the first three months of treatment. During the first three monthsof treatment the upper and lower incisors tipped lingually and the face height increased. Towards the end of treatment theupper incisors proclined and the upper lip became more protrusive. Conclusion: The therapy corrected the horizontal skeletal and arch discrepancies and improved the positions of the lips.(Aust Orthod J 2010; 26: 78–83)

Received for publication: October 2009Accepted: February 2010

Guilherme Thiesen: [email protected] and [email protected] de Oliveira da Luz Fontes: [email protected] Dinah Zastrow: [email protected] Brodbeck May: [email protected]

EFFECTS OF FACEMASK THERAPY


age (Mean age: 7.6 ± 1.9 years) with Class III mal-occlusion. Consecutive subjects were selectedprospectively and treated for nine months. The selec-tion criteria included: Class III malocclusion charac-terised by an anterior crossbite or edge-to-edge incisalrelationship and a Wits appraisal of -2 mm or less; amaxillary deficiency established by facial analysis;20 astage of dental development between late deciduousdentition and mixed dentition; no previous ortho-dontic or orthopaedic treatment; no other cranio-facial anomalies. All subjects were treated before theirpubertal peak in mandibular growth, as verified bythe cervical vertebral maturation method.21 Thestudy was approved by the Ethics Committee of theUniversity of South Santa Catarina.

Cephalometric analysisLateral cephalometric radiographs were taken at thestart of treatment (T1) and at 3-month intervals (T2,T3, T4). The radiographs were taken with the teethin centric relation, and the image magnification was7 per cent. All radiographs were traced and measuredwith digital calipers or protractor by the same opera-tor (G.T.). The linear measurements were recorded tothe nearest 0.1 mm and the angular measurements tothe nearest 0.1 degree. The landmarks and measure-ments used in the study are shown in Figure 1.

Treatment regimen

The upper appliances were a modified Haas rapidmaxillary expansion appliance soldered to bands onthe deciduous second molars or first permanentmolars (Figure 2). When possible, the first premolarswere also banded. Teeth not banded were generallybonded to the appliance with composite resin. Heavy0.045 inch wires joined the palatal appliance andbands and contacted the palatal and buccal surfacesof the posterior teeth. Hooks for extra-oral and inter-maxillary elastics were placed in the buccal wires. Theanterior hooks extended to the canine areas. An 11mm expansion screw, placed in the midline of thepalatal appliance, was activated a quarter turn twicedaily (0.2 mm per turn) until fully activated. At theend of the second week a protraction force of 450 to600 g per side with a downward vector of 30 degreesto the occlusal plane was used. The elastics wereattached to a Petit facemask (Orthotech, PortoAlegre, Brazil) and the subjects were instructed towear the appliance for 12 hours a day.

In the lower ach, a modified 0.045 inch lingual archwas soldered to bands on either the deciduous secondmolars or, generally, the first permanent molars. Thebuccal surfaces of teeth not banded were bonded tothe appliance with composite resin. Buccal 0.045

(a) (b) (c)

Figure 1. Measurements used.(a) Sagittal change in maxilla: SNA, NPerp-A, Co-ASagittal change in mandible: SNB, NPerp-Pog, Co-GnMaxillo-mandibular relationship: ANB, Wits appraisal(b) Vertical relationship: SN/Ocl, SN/PP, SN/GoMe, FMA, ANS-Me(c) Maxillary teeth: 1/NA, 1-NA, 1/PPMandibular teeth: 1/NB, 1-NB, IMPAFacial profile: Steiner ‘S’ line, S-Ul; Steiner ‘S’ line, S-Ll

Po

A

Co

PogGn

N

S

N

ANSU1aPNS

A

U1t

L1a B

Me

Go L1t

UI

LI

Cm

Pog

PNS

N

ANS

U6cL6c U1t L1t

Mo

Go

Po

B

S

OrANB

inch wires were soldered to the lower molar bandsand formed into hooks for Class III intermaxillaryelastics. The hooks extended forwards to the canines.The intermaxillary elastics delivered 200 to 350 g perside and subjects were instructed to use the elastics 24hours per day, only removing them during eating andtooth brushing (Figure 2).

Statistical analysisThe data were normally distributed. The cephalomet-ric measurements were compared at T1, T2, T3 andT4 by the analysis of variance of repetitive measure-ments, since the same individual was analysed at dif-ferent times. Tukey’s HSD test was then used to deter-mine which time intervals were significantly different.The significance level was set at p ≤ 0.05 for all tests.

All measurements were re-traced on two separateoccasions with a 2-week interval between them. Thesystematic error was assessed using a paired t-test andthe combined method errors in location of the land-marks, tracing and measurement with Dahlberg’s for-mula. There was no systematic error and no errorexceeded 0.5 mm or 0.5 degree.

Results

Most of the maxillary sagittal changes occurred in thefirst three months of treatment, as demonstrated bythe SNA angle, NPerp-A and Co-A (Table I). Themaxillary incisors (1/PP) retroclined in the first threemonths then slowly proclined over the following sixmonths. The SNB angle and NPerp-Pog remainedunchanged throughout treatment.

Mandibular length (Co-Gn) increased significantlyfrom T1 to T4. The lower incisors (IMPA) were

tipped progressively lingually from T1 to T4, butthere were no significant changes in 1-NB and 1/NB.The ANB angle and Wits appraisal showed signifi-cant changes in maxillo-mandibular relations from T1 to T4. The greatest changes in these measurements occurred in the first three months of treatment.

There were no significant changes in either FMA orSN/GoMe, indicating that the therapy did notinduce a growth rotation. There was no significantchange in the inclination of the palatal plane to thecranial base (SN/PP), although the lower anteriorfacial height (ANS-Me) and occlusal plane to cranialbase (SN/Ocl) increased throughout treatment (TableI). Small, but statistically significant, changesoccurred in the positions of the lips (S-U1, S-L1),indicating that the soft tissue profile became moreconvex with treatment.

Discussion

Subjects with skeletal Class III malocclusion oftenpresent with concave facial profiles, nasomaxillaryretrusion, and a prominent lower lip and lower thirdof the face. The goal of early treatment is to producethe greatest orthopaedic effect with minimal dentalcompensation. Previous attempts to maximise theorthopaedic effects of facemask therapy have usedfixed splints with elastics, skeletal anchorage withminiplates and ankylosed deciduous canines.25–29

Our treatment protocol of combined maxillaryexpansion, facemask therapy and Class III mechanicsstraightened the skeletal and soft tissue facial profilesof our young subjects with only a few, small dentoalveolar changes, but it was no more successfulthan some of the appliance combinations others have

THIESEN ET AL


(a) (b) (c)

Figure 2. Appliances used in this study for Class III correction:(a) modified Haas expander. (b) modified lingual arch. (c) Class III intermaxillary elastics and extra-oral elastics to the facemask.



used.2,3,7,8,10,12,13,27,29–33 It has been reported thatcombined facemask therapy and Class III mechanicsare no more effective in treating skeletal Class IIImalocclusions than facemask therapy alone.1,2,29,33

In the first three months of treatment the upper incisors tipped palatally and then tipped labially overthe next six months. We attribute the initial palatalmovement of the upper incisors (1/PP) to the maxil-lary expansion, which increased the perimeter of theupper arch, and labial tipping of the upper incisors tothe combined effects of Class III traction and face-mask therapy.34,35 The lower incisors (IMPA) tippedlingually throughout treatment, but the changes,although statistically significant, were less than 4degrees. Pressure from the mandibular pad on thefacemask may be responsible for these changes.

We decided to follow our subjects at 3-month inter-vals because we wanted to determine the incremental

changes with a view to identifying the effects of thevarious components of our therapy. As mentionedabove, maxillary expansion and unwanted pressurefrom the facemask were probably responsible for theincisors tipping lingually in our young subjects.Significant sagittal skeletal modifications occurred inthe first three months of treatment (SNA, NPerp-A,Co-A), although lingual tipping of the lower incisorscould account for some of these changes. After theinitial period, the changes in all three measurementswere maintained until the end of the treatment. A sta-tistically significant increase in the vertical dimension(ANS-Me) also occurred during treatment, but someof this increase (Mean difference: 4.58 mm) may bedue to the mechanics and some to facial growth. Thevertical change was small and may not be of clinicalsignificance.

In this preliminary study, our protocol of maxillaryexpansion, facemask therapy and intermaxillary

Table I. Combined facemask therapy, comparisons at 3-month intervals.

Stages

Measurement T1 T2 T3 T4 p*Mean (SD) Mean (SD) Mean (SD) Mean (SD)

SNA (degrees) 78.12 (2.77) a,b,c 80.36 (3.12) a 80.43 (2.63) b 80.44 (3.11) c 0.0001NPerp-A (mm) -0.53 (2.69) a,b,c 2.31 (2.14) a 2.32 (2.41) b 2.49 (2.29) c <0.0001Co-A (mm) 82.98 (3.21) a,b,c 85.55 (3.09) a,d 86.07 (3.06) b 86.94 (3.09) c,d <0.0001SNB (degrees) 80.56 (3.11) 79.17 (3.23) 79.31 (2.81) 79.14 (3.74) 0. 077NPerp-Pog (mm) -0.11 (4.72) -0.53 (5.01) -0.16 (4.70) 0.02 (4.79) 0.098Co-Gn (mm) 110.77 (5.91) a 111.35 (6.31) 111.99 (7.40) 112.75 (8.17) a 0.006ANB (degrees) -2.44 (2.81) a,b,c 1.19 (2.56) a 1.12 (2.71) b 1.30 (3.29) c <0.0001Wits (mm) -5.70 (3.17) a,b,c -0.05 (4.21) a 0.18 (4.03) b 0.25 (3.07) c <0.00011/NA (degrees) 24.87 (3.13) 23.97 (2.98) 24.55 (2.87) 25.03 (3.32) 0.0611-NA (mm) 4.61 (2.77) 4.21 (2.48) 4.35 (2.91) 5.08 (2.49) 0.0591/PP (degrees) 114.98 (6.32) a 112.43 (6.99) a,b 113.37 (6.64) 116.53 (7.01) b 0.0031/NB (degrees) 23.55 (5.78) 22.53 (4.44) 21.54 (6.01) 21.30 (6.20) 0.0991-NB (mm) 3.21 (2.01) 3.02 (2.12) 3.01 (2.14) 2.96 (2.32) 0.171IMPA (degrees) 88.89 (6.13) a,b,c 86.03 (6.21) a 85.83 (6.35) b 85.12 (6.01) c 0.001SN/Ocl (degrees) 19.36 (6.74) 19.76 (6.87) a 16.02 (7.31) a 17.51 (8.39) 0.029SN/PP (degrees) 8.31 (3.23) 7.67 (3.10) 7.76 (3.05) 8.31 (3.28) 0.606SN/GoMe (degrees) 37.88 (4.64) 40.01 (4.89) 38.87 (5.05) 38.96 (5.53) 0.082FMA (degrees) 26.21 (5.14) 27.63 (5.97) 26.43 (4.66) 25.84 (5.26) 0.075ANS-Me (mm) 61.11 (5.60) a,b,c 64.60 (5.35) a,d 65.17 (4.98) b 65.89 (5.19) c,d <0.0001S-Ul (mm) -0.45 (2.98) a,b 0.25 (3.10) c 0.96 (3.17) a,d 1.98 (2.73) b,c,d 0.0003S-Ll (mm) 1.88 (3.92) a 0.32 (3.43) 0.45 (3.41) 0.68 (3.61) a 0.040

Means followed by the same letter are statistically different*ANOVA, significant values in bold.

mechanics resulted in the skeletal changes and pro-gressive dental compensations we were aiming for.Although most of the changes occurred in the firstthree months of treatment, sustained treatment isessential to correct the overjet and molar relationshipsand maintain the skeletal correction. Ideally, Class IIImalocclusions in young subjects should be overcor-rected and retained as facial growth can undo anyfavourable changes.14,16,18 Further studies arerequired to determine the amount of overcorrectionrequired, the length of retention, the effects of nor-mal facial growth and the contributions made by thevarious appliances. Moreover, the limitations in thepresent study, such as the small sample size and thelack of untreated control group should be mentioned.

Conclusions

Correction of a skeletal Class III malocclusion inyoung subjects with combined facemask therapy,maxillary expansion and intermaxillary mechanicsresulted from forward movement of the maxilla andincisor tipping. The most significant skeletal modifi-cations occurred in the first three months of treat-ment. The therapy improved the positions of the lipsand resulted in a more convex profile.


Professor Guilherme ThiesenAv. Madre Benvenuta1285 - Santa Mônica CEP: 88035-001Florianópolis – SCBrazilEmail: [email protected]

and [email protected]

References1. Kapust AJ, Sinclair PM, Turley PK. Cephalometric effects of

face mask/expansion therapy in Class III children: a com-parison of three age groups. Am J Orthod DentofacialOrthop 1998;113:204–12.

2. Kim J, Viana MA, Graber TM, Omerza FF, BeGole EA. Theeffectiveness of protraction face mask therapy: a meta-analysis.Am J Orthod Dentofacial Orthop 1999;115:675–85.

3. Ngan P, Wei SH, Hägg U, Yiu C, Merwin D, Stickel B.Effect of protraction headgear on Class III malocclusion.Quintessence Int 1992;23:197–207.

4. Guyer EC, Ellis EE, McNamara JA, Behrents RG.Components of Class III malocclusion in juveniles and ado-lescents. Angle Orthod 1986;56:7–30.

5. Battagel JM. The aetiological factors in Class III mal-occlusion. Eur J Orthod 1993;15:347–70.

6. Baccetti T, McGill JS, Franchi L, McNamra JA, Tollaro I.Skeletal effects of early treatment of Class III malocclusionwith maxillary expansion and face-mask therapy. Am JOrthod Dentofacial Orthop 1998;113:333–43.

7. Gallagher RW, Miranda F, Buschang PH. Maxillary protrac-tion: treatment and posttreatment effects. Am J OrthodDentofacial Orthop 1998;113:612–19.

8. Cha KS. Skeletal changes of maxillary protraction inpatients exhibiting skeletal Class III malocclusion: a com-parison of three skeletal maturation groups. Angle Orthod2003;73:26–35.

9. Nartallo-Turley PE, Turley PK. Cephalometric effects ofcombined palatal expansion and facemask therapy on ClassIII malocclusion. Angle Orthod 1998;68:217–24.

10. Ngan P, Yiu C, Hu A, Hägg U, Wei SH, Gunel E.Cephalometric and occlusal changes following maxillaryexpansion and protraction. Eur J Orthod 1998;20:237–54.

11. Ngan P, Hägg U, Yiu C, Wei SH. Treatment response andlong-term dentofacial adaptations to maxillary expansionand protraction. Semin Orthod 1997;3:255–64.

12. da Silva Filho OG, Magro AC, Capelozza Filho L. Earlytreatment of the Class III malocclusion with rapid maxillaryexpansion and maxillary protraction. Am J OrthodDentofacial Orthop 1998;113:196–203.

13. Sung SJ, Baik HS. Assessment of skeletal and dental changesby maxillary protraction. Am J Orthod Dentofacial Orthop1998;114:492–502.

14. Baccetti T, Franchi L, McNamara JR. Cephalometric vari-ables predicting the long-term success or failure of com-bined rapid maxillary expansion and facial mask therapy.Am J Orthod Dentofacial Orthop 2004;126:16–22.

15. Ghiz MA, Ngan P, Gunel E. Cephalometric variables to pre-dict future success of early orthopedic Class III treatment.Am J Orthod Dentofacial Orthop 2005;127:301–6.

16. Hägg U, Tse A, Bendeus M, Rabie AB. Long-term follow-upof early treatment with reverse headgear. Eur J Orthod 2003;25:95–102.

17. Wells AP, Sarver DM, Proffit WR. Long-term efficacy ofreverse pull headgear therapy. Angle Orthod 2006;76:915–22.

18. Westwood PV, McNamara JA, Baccetti T, Franchi L, SarverDM. Long-term effects of Class III treatment with rapidmaxillary expansion and facemask therapy followed by fixedappliances. Am. J Orthod Dentofacial Orthop 2003;123:306–20.

19. Holberg C, Mahaini L, Rudzki I. Analysis of sutural strainin maxillary protraction therapy. Angle Orthod 2007;77:586–94.

20. Staudt CB, Kiliaridis S. A nonradiographic approach todetect Class III skeletal discrepancies. Am J OrthodDentofacial Orthop 2009;136:52–9.

21. Baccetti T, Franchi L, McNamara JA Jr. The CervicalVertebral Maturation (CVM) method for the assessment ofoptimal treatment timing in dentofacial orthopaedics SeminOrthod 2005;11:119–29.

22. Bjork A. The face in profile. Svensk Tandi Tidskr 1947;40:Suppl.

23. Odergaard J. Growth of the mandible studied with the aid ofmetal implant. Am J Orthod 1970;57:145–57.

24. Riolo ML, Moyers RE, McNamara JA Jr, Hunter WS. Anatlas of craniofacial growth: cephalometric standards fromthe University School Growth Study, The University ofMichigan. Monograph No 2. Craniofacial Growth Series.Ann Arbor: Center for Human Growth and Development,The University of Michigan; 1974.

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25. Ferro A, Nucci LP, Ferro F, Gallo C. Long-term stability ofskeletal Class III patients treated with splints, Class III elas-tics, and chincup. Am J Orthod Dentofacial Orthop 2003;123:423–34.

26. Hong H, Ngan P, Han G, Qi LG, Wei SH. Use of onplantsas stable anchorage for facemask treatment: a case report.Angle Orthod 2005;75:453–60.

27. Kircelli BH, Pektas ZÖ, Uçkan S. Orthopedic protractionwith skeletal anchorage in a patient with maxillary hypo-plasia and hypodontia. Angle Orthod 2006;76:156–63.

28. Liou EJ, Tsai WC. A new protocol for maxillary protractionin cleft patients: repetitive weekly protocol of alternate rapidmaxillary expansions and constrictions. Cleft PalateCraniofac J 2005;42:121–7.

29. da Silva Filho OG, Osawa TO, Okada CH, Okada HY,Dahmen L. Anquilose intencional dos caninos decíduoscomo reforço de ancoragem para a tração reversa da maxila.Estudo cefalométrico prospectivo. Dental Press OrtodonOrtop Facial 2006;11:35–44.

30. Baik HS. Clinical results of maxillary protraction in Koreanchildren. Am J Orthod Dentofacial Orthop 1995;108:583–92.

31. Pangrazio-Kulbersh V, Berger J, Kersten G. Effects of pro-traction mechanics on the midface. Am J OrthodDentofacial Orthop 1998;114:484–91.

32. Saadia M, Torres E. Sagital changes after maxillary protrac-tion with expansion in Class III patients in the primary,mixed and late mixed dentitions: a longitudinal retrospec-tive study. Am J Orthod Dentofacial Orthop 2000;117:669–80.

33. Macdonald KE, Kapust AJ, Turley PK. Cephalometricchanges after the correction of Class III malocclusion withmaxillary expansion facemask therapy. Am J OrthodDentofacial Orthop 1999;116:13–24.

34. Chung C, Font B. Skeletal and dental changes in the sagit-tal, vertical, and transverse dimensions after rapid palatalexpansion. Am J Orthod Dentofacial Orthop 2004;126:569–75.

35. Wertz RA. Skeletal and dental changes accompanying rapidmidpalatal suture opening. Am J Orthod 1970;58:41–66.

Introduction

For more than 40 years researchers have been work-ing to improve the bonding of orthodontic bracketsto teeth. Recent developments have been the intro-duction of self-etching primers (SEP), originallyintended for use in operative dentistry, to success-fully bond orthodontic brackets.1–3 These primerscause less aggressive decalcification and less enamelloss than traditional phosphoric acid etchants, are lessaffected by humidity, prevent contamination withsaliva and are quick to apply.3,4 It has also beenreported that although these primers result in short enamel tags, brackets bonded after enamel

conditioning with SEPs have adequate shear bondstrengths and, in many instances, less adhesiveremains on the teeth after debonding.5 As a rule theyare combined with a light-cured adhesive whichenables brackets to be ‘tacked’ immediately in position.6

To our knowledge, Transbond Plus SEP (TPSEP) isthe only SEP that does not significantly affect theshear bond strength (SBS) of orthodontic brackets.5In light of the great diversity in ultrastructure, fillercontent, microhardness and chemical composition ofdifferent orthodontic adhesives,7 and the possibilitythat TPSEP may not behave favourably with all


Bond strengths of different orthodontic adhesivesafter enamel conditioning with the same self-etching primer

Rogelio J. Scougall-Vilchis,* Chrisel Zárate-Díaz,† Shusuke Kusakabe+ and KohjiYamamoto+

Department of Orthodontics, School of Dentistry, Autonomous University State of Mexico,* Private Practice, Toluca City, Mexico† and theDivision of Oral Functional Sciences and Rehabilitation, School of Dentistry, Asahi University, Japan+

Aim: To determine the shear bond strengths (SBS) of stainless steel brackets bonded with seven light-cured orthodontic adhesivesafter the enamel was conditioned with the same self-etching primer.Methods: A total of 140 extracted human molars were randomly divided into seven groups (N = 20). In all the groups, theenamel was conditioned with Transbond Plus SEP (TPSEP). Stainless steel brackets were bonded with the following orthodonticadhesives: Group I, Transbond XT; Group II, Blugloo; Group III, BeautyOrtho Bond; Group IV, Enlight; Group V, Light Bond;Group VI, Transbond CC; Group VII, Xeno Ortho. The teeth were stored in distilled water at 37 °C for 24 hours and debonded with a universal testing machine. The modified adhesive remnant index (ARI) was also recorded.Results: There were no significant differences in the SBS values among the groups: I (18.0 ± 7.4 MPa); II (18.3 ± 5.1 MPa);III (14.8 ± 4.3 MPa); IV (18.3 ± 7.0 MPa); V (16.4 ± 4.3 MPa); VI (20.3 ± 5.3 MPa); VII (15.9 ± 6.4 MPa), but significantdifferences in ARI were found.Conclusions: The seven orthodontic adhesives evaluated in this study can be successfully used for bonding stainless steel brackets when the enamel is conditioned with TPSEP, however, the differences among some groups might influence the clinicalbond strengths. In addition, the amount of residual adhesive remaining on the teeth after debonding differed among the adhesives. Further studies are required to better understand the differences in SBS and ARI.(Aust Orthod J 2010; 26: 84–89)

Received for publication: December 2008 Accepted: February 2010

Rogelio J. Scougall-Vilchis: [email protected] Zárate-Díaz: [email protected] Kusakabe: [email protected] Yamamoto: [email protected]

BOND STRENGTHS OF DIFFERENT ADHESIVES WITH THE SAME SEP


adhesives, we decided to determine the bondstrengths of seven readily available light-cured ortho-dontic adhesives on the SBS of stainless steel bracketsafter the enamel was conditioned with TPSEP.


One hundred and forty extracted human molars werecollected and stored in a solution of 0.2 per cent(wt/vol) thymol to prevent bacterial growth, untilrequired. The criteria for tooth selection included:molars with intact enamel surfaces, no white spotlesions and no history of orthodontic treatment orchemical treatment for bleaching.8 The teeth wererinsed with water and cleaned with a fluoride-freepaste (Pressage, Shofu Incorporated, Kyoto, Japan)and rubber prophylactic cups (Merssage, ShofuIncorporated, Kyoto, Japan) in a slow-speed hand-piece. The teeth were then washed with water for 30seconds and air-dried.

One hundred and forty stainless steel 0.018 inch,standard edgewise, upper incisor brackets (TomyInternational, Tokyo, Japan) were used. The averagesurface area of the bases of 10 randomly selectedbrackets was 13.58 mm2.

The teeth were randomly divided into seven groups(N = 20 per group). The buccal surface of each toothwas conditioned with TPSEP (3M Unitek,Monrovia, CA, USA) following the manufacturer’sinstructions.5 The TPSEP was rubbed on the enamelsurface for 5 seconds then gently dried with compressed air for a few seconds.

The brackets were bonded with different light-cureorthodontic adhesives (Table I). Immediately afterthe brackets were placed, they were light-cured

(BlueLex, Yoshida Dental, Tokyo, Japan) for a total of 20 seconds (10 seconds on the mesial edge of the bracket and 10 seconds on the distal edge). Allprocedures were performed by the same researcher.

SBS testAfter bonding, a short length of 0.017 x 0.025 inchstainless steel wire was ligated into each bracket slotto reduce deformation of the bracket during debond-ing. The teeth were embedded in acrylic resin andmounted in the universal testing machine (EZGraph, Shimazdu, Kyoto, Japan) with the labial surfaces parallel to the debonding force.

An occluso-gingival load was applied to each bracket,producing a shear force at the bracket – tooth inter-face. This was accomplished with the flattened end ofa steel rod attached to the crosshead of the universaltesting machine. The SBS was measured at acrosshead speed of 0.5 mm/min and the load appliedat fracture was recorded in newtons (N) and convert-ed to megapascals (MPa) by dividing the load by themean area of the bracket bases (13.58 mm2).Following debonding, the teeth were stored in distilled water at 37 °C for 24 hours.9

Modified adhesive remnant indexThe enamel surface of each molar was inspected atx10 magnification and the amount of residual adhes-ive remaining on the surface of the tooth scored withthe modified ARI: 1, all composite remained on thetooth; 2, more than 90 per cent of the compositeremained on the tooth; 3, between 10 and 90 per centof the composite remained on the tooth; 4, less than10 per cent of the composite remained on the tooth;5, no composite remained on the tooth.10

Table I. Orthodontic adhesives used in this study.

Group Orthodontic Manufactureradhesive

I Transbond XT 3M Unitek, Monrovia, CA, USAII Blugloo Ormco Corp., Glendora, CA, USAIII BeautyOrtho Bond Shofu Inc., Kyoto, JapanIV Enlight Ormco Corp., Glendora, CA, USAV Light Bond Reliance Orthodontic Products,

Itasca, IL, USAVI Transbond CC 3M Unitek, Monrovia, CA, USAVII Xeno Ortho Dentsply-Sankin K.K., Tochigi,

Japan

Table II. Comparisons of the shear bond strengths of the adhesives.

Group N Mean (MPa) SD Range

I Transbond XT 20 18.0 7.4 8.3 - 34.9II Blugloo 20 18.3 5.1 11.3 - 30.5III BeautyOrtho Bond 20 14.8 4.3 7.8 - 21.0IV Enlight 20 18.3 7.0 7.6 - 30.5V Light Bond 20 16.4 4.3 5.4 - 31.0VI Transbond CC 20 20.3 5.3 9.0 - 26.7VII Xeno Ortho 20 15.9 6.4 5.8 - 27.1

ANOVA, p > 0.05

SCOUGALL-VILCHIS ET AL


Statistical analysisThe SBS data were compared with a one-wayANOVA and post-hoc Scheffe tests. The significancein both tests was predetermined at p < 0.05. The distributions of ARI scores were compared with a chi-squared test.

Results

The SBS values and the descriptive statistics are pre-sented in Table II. The mean SBS in all the groupsexceeded 14.8 MPa and there were no statistically significant differences between the groups (ANOVA: p > 0.05). Groups I (Mean: 18.0 ± 7.4 MPa), II(Mean: 18.3 ± 5.1 MPa), and IV (Mean:18.3 ± 7.0MPa) had comparable mean values of SBS followedby Groups V (Mean: 16.4 ± 4.3 MPa) and VII(Mean: 15.9 ± 6.4 MPa). Group VI (Mean: 20.3 ±5.3 MPa) had the highest mean value and Group III(Mean: 14.8 ± 4.3 MPa) the lowest mean SBS.

The ARI scores are given in Table III. The distribu-tions of adhesive remnants in the groups were signif-icantly different (p = 0.0001). The smallest amountsof adhesive remnant were found in Group I with amean ARI score of 3. This group also had the highestnumber of teeth with a score of 5 and no teeth withscores of 1 or 2. Groups II, IV, V and VI showedcomparable ARI scores, with mean scores of 3. Morethan 90 per cent of the composite remained on thebuccal surfaces (ARI: 2) of between 10 and 15 percent of the teeth in these groups, but no tooth had anARI score of 1. The teeth in Group VII followed byGroup III had the highest amount of adhesive left onthe tooth after debonding: 40 per cent and 10 per

cent, respectively. In these groups there were no teethwith scores of 4 or 5.

Discussion

The SBS values for all TPSEP – composite combina-tions exceeded the range of values (6–8 MPa) con-sidered by some researchers to be a suitable SBS forroutine clinical use.11,12 Stainless steel brackets can besuccessfully bonded with any of the seven adhesiveswe investigated after the enamel is conditioned with TPSEP. However, we found different patterns of adhesive fracture during debonding that may influence the choice of adhesive.

In orthodontic practice, a reliable bond between thebrackets and enamel is essential,13 but as the appli-ances are temporary, methods that avoid damage tothe enamel during bonding and following debondingare desirable.14,15 Self-etching primers for enamelconditioning avoid the decalcification characteristicof phosphoric acid-based agents.16 They provide a‘gentler’ etch pattern, which has been illustrated inseveral SEM studies.4,8,17 We selected TPSEP forenamel conditioning because it is frequently used inorthodontics,18 and brackets bonded to teeth condi-tioned with TPSEP had significantly higher SBSsthan those bonded after the application of otherSEPs.5,19 When different SEPs were used with thesame composite resin we found TPSEP – resin wasthe only combination that did not affect the bondstrength significantly compared to the control group etched with 37 per cent phosphoric acid for 15 seconds.19 When TPSEP was applied for only 3seconds and the brackets debonded after 24 hours,

Table III. Distributions and percentages of adhesive remaining on the teeth after debonding.

Modified ARI scoresCount (Per cent)

Group N 1 2 3 4 5

I Transbond XT 20 0 (0) 0 (0) 10 (50) 5 (25) 5 (25)II Blugloo 20 0 (0) 3 (15) 9 (45) 6 (30) 2 (10)III BeautyOrtho Bond 20 2 (10) 9 (45) 9 (45) 0 (0) 0 (0)IV Enlight 20 0 (0) 2 (10) 8 (40) 7 (35) 3 (15)V Light Bond 20 0 (0) 2 (10) 8 (40) 8 (40) 2 (10)VI Transbond CC 20 0 (0) 4 (20) 11 (55) 5 (25) 0 (0)VII Xeno Ortho 20 8 (40) 7 (35) 5 (25) 0 (0) 0 (0)

χ2 = 81.82; df = 24, p = 0.0001



the orthodontic brackets presented higher SBS valuesthan those in which the enamel had been etched with37 per cent phosphoric acid.9 Furthermore, TPSEPhas also been shown to provide higher 6-month sur-vival rates than brackets bonded after a conventionalacid etch.20 Moreover, it has been shown to provide asuitable bond strength even if it is contaminated withsaliva.21 A recent study reported that activatedTPSEP stored for up to 15 days did not significantlyaffect the SBS of orthodontic brackets.18

The direct bonding of molar tubes is now a commonprocedure in orthodontic practice. In spite of the factthat the buccal surfaces of human molars have com-plex and variable shapes, the seven adhesives we eval-uated yielded higher SBSs than considered adequateto accomplish treatment.11,12 Although we foundthere were no significant differences between theTPSEP – adhesive combinations, thermal stresses cansignificantly reduce the bond strength of TPSEP anda longer study may have disclosed differences betweenthe groups.22 The SBS was variable in Groups I, IV,and VII: findings that are consistent with a previousstudy in which the enamel was conditioned withTPSEP and the brackets were bonded withTransbond XT.5 Groups I (Transbond XT), II(Blugloo), and IV (Enlight) had approximately thesame mean SBS values. A larger mean difference(slightly >5 MPa) was found between Groups VI(Transbond CC: 20.3 MPa) and III (BeautyOrthoBond: 14.8 MPa). An interesting finding was thehigher SBS value in Group VI (Transbond CC) whencompared with Group I (Transbond XT). AsTransbond CC is a fluoride-releasing adhesive, weexpected a lower SBS value than that obtained withTransbond XT, but there was no significant differencebetween the two resins. The concentration of fluoridein Transbond CC did not appear to influence thebond strength of the resin under the conditions inour study.

As ceramic brackets have higher bond strengths thanstainless steel brackets, an adhesive with a low SBS,such as BeautyOrtho Bond or Xeno Ortho, may bepreferable to adhesives with high bond strengths.20,23

The bond strengths of stainless steel and ceramicbrackets can be raised by treating the bracket padwith a silicone product and altered by using a differ-ent etchant or by applying a caries-protective resinafter etching.25–27 Light Bond demonstrated slightlyhigher SBS than Transbond XT when the enamel was

etched with phosphoric acid,26 and Blugloo pre-sented lower shear peel bond strength than Trans-bond XT.27 Light Bond had a significantly higherSBS than both Transbond XT and Blugloo after acaries protective sealant was applied.27 With the com-binations of TPSEP and resins we used, proceduresthat increase the SBS appear to be unnecessary as thebond strength values exceeded those considered to beappropriate for most clinical procedures, but theremay be some advantages if the site of failure occurs atthe resin – enamel interface.

Although frequently used, the ARI is a problematicparameter and the results should be regarded cautiously. It has been demonstrated that the amountof adhesive remaining on the tooth tends to be largerwhen a high SBS value is obtained.5,28 However, ourfindings are slightly contradictory as significantlymore adhesive was found in the groups with low SBSvalues (Groups VII and III). In these groups, bracketfailure frequently occurred at the bracket – adhesiveinterface. Pretreatment that enhances the visibility ofthe resin flash or the bond strength at the resin –bracket interface might reduce the amount of adhesive left on the tooth after debonding and/or theamount of time spent removing resin remnants.24 Acolouring agent in the resin flash has been tried.29

With improvements in the physical and mechanicalproperties of composite resins, removing the adhesiveremnants after debonding has become a clinical problem. Resin remnants may discolour over timeand retain plaque.30 Tooth cleaning is easier and fasterand iatrogenic damage during cleaning is less likely tooccur when brackets fail at the enamel – resin inter-face.5,10,31 However, bond failure at the bracket –adhesive interface or within the adhesive is consideredto be safer than failure at the enamel – adhesive inter-face because enamel fracture can occur if failureoccurs at the latter site.10

Apart from enamel fracture or gouges from injudi-cious use of hand instruments or burs, the enamel lostduring orthodontic procedures is insignificant interms of the total thickness of the enamel.32

Nevertheless, enamel loss at the time of bracketremoval depends largely on the orthodontic materialsused, the method of debonding, the tactile ability ofthe clinician and the instruments used.20,32 Leastenamel loss occurs when TPSEP is used and theenamel cleaned with a slow-speed tungsten carbidebur.28

Conclusions

Under the conditions of this in-vitro study, the following conclusions were drawn:

1. The seven orthodontic adhesives and TPSEP hadSBS values that exceeded the range of values (6–8MPa) considered by some researchers to be suitablefor routine clinical use.

2. Stainless steel brackets can be successfully bondedwith any of these adhesive pastes when the enamel isconditioned with TPSEP.

3. Less adhesive was found on the teeth whenTransbond XT, Blugloo, Enlight, Light Bond andTransbond CC were used.

4. Further in vivo and in-vitro studies are necessary todetermine the effects of time on the shear bondingstrengths and sites of fracture of the resin – TPSEPcombinations we studied.


Professor Rogelio J. Scougall-Vilchis Department of OrthodonticsSchool of DentistryAutonomous University State of MexicoFrancisco Carbajal Bahena #241Col. Morelos, Z.C. 50120Toluca CityMéxicoTel: (+52) 722-280-91-13Email: [email protected]

References1. Bishara SE, VonWald L, Laffoon JF, Warren JJ. Effect of a

self-etch primer/adhesive on the shear bond strength oforthodontic brackets. Am J Orthod Dentofacial Orthop2001;119:621–4.

2. Tecco S, Traini T, Caputi S, Festa F, de Luca V, D’Attilio M.A new one-step dental flowable composite for orthodonticuse: an in vitro bond strength study. Angle Orthod 2005;75:672–7.

3. Bishara SE, Otsby AW, Ajlouni R, Laffoon J, Warren JJ. Anew premixed self-etch adhesive for bonding orthodonticbrackets. Angle Orthod 2008;78:1101–14.

4. Fjeld M, Øgaard B. Scanning electron microscopic evalua-tion of enamel surfaces exposed to 3 orthodontic bondingsystems. Am J Orthod Dentofacial Orthop 2006;130:575–81.

5. Scougall-Vilchis RJ, Yamamoto S, Kitai N, Yamamoto K.Shear bond strength of orthodontic brackets bonded withdifferent self-etching adhesives. Am J Orthod DentofacialOrthop 2009;136:425–30.

6. Oesterle LJ, Newman SM, Shellhart WC. Comparative bondstrength of brackets cured using a pulsed xenon curing lightwith 2 different light-guide sizes. Am J Orthod DentofacialOrthop 2002;122:242–50.

7. Scougall-Vilchis RJ, Hotta Y, Yamamoto K. Examination ofsix orthodontic adhesives with electron microscopy, hard-ness tester and energy dispersive x-ray micro analyzer. AngleOrthod 2008;78:655–61.

8. Bishara SE, Soliman M, Laffoon J, Warren JJ. Effect ofantimicrobial monomer-containing adhesive on shear bondstrength of orthodontic brackets. Angle Orthod 2005;75:397–9.

9. Türk T, Elekdag-Türk S, Isci D. Effects of self-etchingprimer on shear bond strength of orthodontic brackets atdifferent debond times. Angle Orthod 2007;77:108–12.

10. Bishara SE, Ostby AW, Ajlouni R, Laffoon JF, Warren JJ.Early shear bond strength of a one-step self-adhesive onorthodontic brackets. Angle Orthod 2006;76:689–93.

11. Ogaard B, Bishara SE, Duschner H. Enamel effects duringbonding-debonding and treatment with fixed appliances. In:Graber TM, Eliades T, Athanasiou AE, eds. Risk manage-ment in orthodontics: experts guide to malpractice. CarolStream, Ill: Quintessence Publishing Co Inc, 2004;19–46.

12. Powers JM, Messersmith ML. Enamel etching and bondstrength. In: Brantley WA, Eliades T, eds. Orthodonticmaterials: scientific and clinical aspects. Stuttgart, Germany:Thieme, 2001;105–22.

13. Kim MJ, Lim BS, Chang WG, Lee YK, Rhee SH, Yang HC.Phosphoric acid incorporated with acidulated phosphate fluoride gel etchant effects on bracket bonding. AngleOrthod 2005;75:678–84.

14. Pasquale A, Weinstein M, Borislow AJ, Braitman LE. In-vivoprospective comparison of bond failure rates of 2 self-etch-ing primer/adhesive systems. Am J Orthod DentofacialOrthop 2007;132:671–4.

15. Arhun N, Arman A, Cehreli SB, Arikan S, Karabulut E,Gülsahi K. Microleakage beneath ceramic and metal brack-ets bonded with a conventional and an antibacterial adhesivesystem. Angle Orthod 2006;76:1028–34.

16. Attar N, Taner TU, Tülümen E, Korkmaz Y. Shear bondstrength of orthodontic brackets bonded using conventionalvs one and two step self-etching/adhesive systems. AngleOrthod 2007;77:518–23.

17. Cal-Neto JP, Miguel JA. Scanning electron microscopy eval-uation of the bonding mechanism of a self-etching primeron enamel. Angle Orthod 2006;76:132–6.

18. Pithon MM, de Oliveira Ruellas AC, Sant’Anna EF, deOliveira MV, Alves Bernardes LA. Shear bond strength ofbrackets bonded to enamel with a self-etching primer:effects of increasing storage time after activation. AngleOrthod 2009;79:133–7.

19. Scougall-Vilchis RJ, Ohashi S, Yamamoto K. Effects of self-etching primers on shear bond strength of orthodonticbrackets. Am J Orthod Dentofacial Orthop 2009;135:424.e1–.e7.

20. dos Santos JE, Quioca J, Loguercio AD, Reis A. Six-monthbracket survival with a self-etch adhesive. Angle Orthod2006;76:863–8.

21. Dunn WJ. Shear bond strength of an amorphous calcium-phosphate–containing orthodontic resin cement. Am JOrthod Dentofacial Orthop 2007;131:243–7.

22. Elekdag-Turk S, Turk T, Isci D, Ozkalayci N. Thermocyclingeffects on shear bond strength of a self-etching primer.Angle Orthod 2008;78:351–6.

23. Uysal T, Ulker M, Ramoglu SI, Ertas H. Microleakage undermetallic and ceramic brackets bonded with orthodontic self-etching primer systems. Angle Orthod 2008;78:1089–94.

24. Atsü SS, Gelgör IE, Sahin V. Effects of silica coating andsilane surface conditioning on the bond strength of metal

SCOUGALL-VILCHIS ET AL




and ceramic brackets to enamel. Angle Orthod 2006;76:857–62.

25. Yamamoto A, Yoshida T, Tsubota K, Takamizawa T,Kurokawa H, Miyazaki M. Orthodontic bracket bonding:enamel bond strength vs time. Am J Orthod DentofacialOrthop 2006;130:435.e1–6.

26. Vicente A, Bravo LA, Romero M, Ortíz AJ, Canteras M.Effects of 3 adhesion promoters on the shear bond strengthof orthodontic brackets: an in-vitro study. Am J OrthodDentofacial Orthop 2006;129:390–5.

27. Lowder PD, Foley T, Banting DW. Bond strength of 4orthodontic adhesives used with a caries-protective resinsealant. Am J Orthod Dentofacial Orthop 2008;134:291–5.

28. Hosein I, Sherriff M, Ireland AJ. Enamel loss during bond-ing, debonding, and cleanup with use of a self-etchingprimer. Am J Orthod Dentofacial Orthop 2004;126:717–24.

29. Armstrong D, Shen G, Petocz P, Darendeliler MA. Excessadhesive flash upon bracket placement: a typodont studycomparing APC plus and transbond XT. Angle Orthod2007;77:1101–8.

30. Kim SS, Park WK, Son WS, Ahn HS, Ro JH, Kim YD.Enamel surface evaluation after removal of orthodonticcomposite remnants by intraoral sandblasting: a 3-dimen-sional surface profilometry study. Am J Orthod DentofacialOrthop 2007;132:71–6.

31. Al Shamsi A, Cunningham JL, Lamey PJ, Lynch E. Shearbond strength and residual adhesive after orthodontic brack-et debonding. Angle Orthod 2006;76:694–9.

32. Al Shamsi AH, Cunningham JL, Lamey PJ, Lynch E. Three-dimensional measurement of residual adhesive and enamelloss on teeth after debonding of orthodontic brackets: an in-vitro study. Am J Orthod Dentofacial Orthop 2007;131:301.e9–15.

IntroductionSuccessful management of a tooth with the root frac-tured below the crest of the alveolar bone requires thecooperation of professionals with different knowledgeand skills. The options for treatment include: removalof the fractured root and placement of either arestoration, implant or prosthesis;1–5 periodontalreconstruction, ranging from a simple gingivectomyto surgical exposure of the fracture line;2,6–8 ortho-dontic extrusion with or without periodontal surgery.2,6–8 The principal aim of orthodontic extru-sion is to restore the relationship between the rootfragment, the crest of the alveolar bone and the gin-gival tissues.9,10 The final choice of therapy dependson the level and angle of the fracture line and thelength of the apical root fragment.11

When the fracture occurs in the middle third of theroot, the prognosis is unfavourable because theextruded and restored root fragment is unable toresist normal functional loads.12 On the other hand,if the fracture level is more-or-less horizontal andclose to the alveolar crest and providing the tooth hasnot been displaced, periodontal surgery is usually the

most appropriate form of treatment. If, however, thefracture line is more apically placed and periodontaltreatment will lead to loss of alveolar bone and anunsightly appearance,9,13 a practicable option is toextrude the apical root fragment. New bone isdeposited behind the extruded root fragment and theroot fragment – alveolar bone – gingival tissue rela-tionships are restored.12–14 Often periodontal surgeryis required after extrusion to recontour the gingivaltissues.9,13

The aim of this report is to describe the multi-disciplinary management of a fractured upper lateralincisor requiring extrusion, periodontal surgery andrestoration.

Case report

A 30 year-old male was referred to the postgraduateclinic at the Dental School, Araçatuba, São PauloState University, following a blow to the upper left lateral incisor. The patient complained of painand the tooth, which had been restored with a por-celain post-crown, was very mobile. The gingivaewere inflamed and there appeared to be a fistula


Multidisciplinary treatment of a fractured root: a case report

Osmar Aparecido Cuoghi,* Álvaro Francisco Bosco,† Marcos Rogério de Mendonça,*

Pedro Marcelo Tondelli* and Yésselin Margot Miranda-Zamalloa*

Departments of Pediatric and Community Dentistry* and Surgery and Integrated Clinic,† Dental School of Araçatuba, São Paulo StateUniversity, Araçatuba, Brazil.

Aim: To describe the orthodontic, periodontal and prosthetic management of a case with a 3 mm root fracture below the crestof the alveolar bone.Methods: The root was extruded and periodontal surgery carried out to improve aesthetics and dental function.Conclusion: A multidisciplinary approach to the management of dental root fractures is necessary for successful treatment.(Aust Orthod J 2010; 26: 90–94)

Received for publication: October 2009Accepted: January 2010

Osmar Aparecido Cuoghi: [email protected]Álvaro Francisco Bosco: [email protected] Rogério de Mendonça: [email protected] Marcelo Tondelli: [email protected]ésselin Margot Miranda-Zamalloa: [email protected]

MULTIDISCIPLINARY TREATMENT OF A FRACTURED ROOT


about 3-4 mm above the labial gingival margin. Anintra-oral radiograph confirmed that the root andalveolar bone had been fractured about 3 mm belowthe alveolar crest and the coronal fragment displacedmesio-occlusally (Figure 1).

The treatment objectives were to remove the coronalfragment, extrude the apical fragment until the frac-ture level was about 3 mm beyond the alveolar crest,fabricate a new post-crown and, if necessary, carry out a gingivoplasty to recontour the gingival tissues.We estimated approximately 6 mm of extrusion was required for the fracture line to reach the desiredposition.

The coronal fragment was removed under localanaesthesia, and a short length of 0.7 mm stainlesssteel wire with a small ‘J’ hook in the coronal end wascemented in the root canal with composite resin. Asecond length of 0.7 mm stainless steel wire with apalatal loop and an acrylic crown was bonded withcomposite resin (Concise, Unitek 3M, Monrovia,CA, USA) to the adjacent teeth. This temporaryreplacement maintained space for the future crownand served as anchorage to extrude the apical frag-ment. Dental floss was tied between the loop in thehorizontal wire and the ‘J’ hook. The loop was care-fully sited to ensure that extrusion occurred along thelong axis of the apical fragment. After one month the

floss tie was replaced with a one-eighth inch elastic:this was renewed weekly.

Over the following fortnight, the distance betweenthe hook and loop reduced, and the short elastic wasreplaced with elastic chain. After six weeks, the apicalfragment had extruded approximately 3 mm and thegingival tissues appeared to be healthy (Figure 2). Theroot fragment was now fixed by passing a wire liga-ture between the hook and the horizontal section ofwire.

After three months retention, an additional perio-dontal procedure was undertaken to restore theheight of the alveolar bone and to recontour the gin-gival tissues. A partial thickness labial flap and a fullthickness palatal flap were raised and a small osteo-tomy carried out to recontour the crestal bone. Bothflaps were then repositioned apically and sutured inplace (Figure 3). The patient was prescribed analgesics(Acetaminophen 750 mg, Johnson and Johnson, SãoPaulo, Brazil) and a daily 0.12 per cent chlorhexidinemouthrinse. The sutures were removed after sevendays and healing occurred without any complications(Figure 3). The ‘J’ hook was removed and the rootcanal prepared for the final post-crown (Figures 4 and5). Clinical and radiographic examination indicatedthat all aesthetic and functional objectives had beenmet and that new bone had been deposited in thesocket and on the alveolar crest (Figure 4).

Discussion

Teeth fractured at the level of the marginal gingivaeor below the crest of the alveolar bone are usually

Figure 2. The root fragment, ‘J’ hook and temporary wire bar after six weeksextrusion. The temporary crown has been removed.

Figure 1. The fractured tooth, showing the fracture 3 mm below the alveolarcrest and the displaced crown.

treated with periodontal surgery and/or orthodonticextrusion of the apical root fragment. The intentionis to restore the gingival sulcus to approximately 1 mm and the distance between the bottom of thesulcus and the alveolar crest to about 2 mm. Thus, 3 mm is considered to be the minimum distancebetween the top of the alveolar crest and the gingivalmargin. In the case we have presented the fractureoccurred approximately 3 mm below the crest of thealveolar bone necessitating 6 mm of extrusion.

Removing crestal bone without extruding the rootcan compromise both the aesthetics (the crown mustbe larger) and the crown-root ratio.15 If, on the otherhand, the apical fragment is extruded orthodontically

the root will be shorter, but the dimensions of thecrown will be unchanged and the aesthetics andcrown-root ratio maintained. Whatever therapeuticprocedure is adopted, at the end of rehabilitation thecrown-root ratio should be approximately 1:1.

How does one decide if extrusion of an apical rootfragment is the best course of action? Ideally, only oneor two teeth should be involved and the fractureshould be in the coronal third of the root.12 To deter-mine the suitability of the present case for extrusionwe divided the overall length of the tooth on a longcone periapical radiograph into eight equal parts. Fiveparts corresponded to the root length and three partsto the crown length. This indicated to us that we

CUOGHI ET AL


(a) (b)

Figure 3. (a) The root fragment immediately after periodontal surgery. (b) Two weeks later.

(a) (b)

Figure 4. Periapical radiographs. (a) At the start of extrusion and eight weeks later. (b) After periodontal surgery and the final post-crown.

MULTIDISCIPLINARY TREATMENT OF A FRACTURED ROOT


could extrude the root 3 to 4 mm and still have aminimum crown-root ratio of 1:1. The crown wasoriginally three-eighths of the length of the intacttooth: after extrusion it was three-sevenths of therestored tooth (Figure 6).

Upper central incisors have a mean crown length of 12 mm and a mean root length of 16 mm. Upperlateral incisors, on the other hand, have a mean crown length of 9 mm and a mean root length of 15 mm.16 Considering the crown-root ratios of theseteeth, the central and lateral incisors can be extruded4 and 6 mm, respectively. The upper central incisorsare more likely to be fractured, but upper lateral incisors have a more favourable crown-root ratio forextrusion.

Following approximately 3 mm extrusion we retainedthe tooth for three months to allow bone to bedeposited behind the extruded tooth and reducerelapse (Figure 4). We then recontoured the bone toposition the root face 3 mm above the alveolar crest.Although the root was shorter the new crown-rootratio was 3:4 and aesthetics were not compromised(Figures 5 and 6).

More bone may be deposited during slow extrusionthan during rapid extrusion. Providing extrusion doesnot exceed 2 mm per month, deposition of new boneproceeds at a satisfactory rate. It has been reportedthat high forces and a faster rate of extrusion, approx-imately 1 mm per week, were accompanied byreduced migration of the supporting tissues, less newbone cervically and ankylosis.17–19

The periodontal fibres, in particular the marginal andapical fibres, may be ‘stretched’ during extrusion and

remained stretched for some months.20 If a supra-crestal fibrotomy is carried out shortly after extrusionsome additional extrusion will occur, but it may beaccompanied by less new cervical bone, gingival reces-sion and loss of periodontal attachment.14,17,21–23

Low magnitude forces in the region of 15 to 30 cNextrude a tooth slowly and promote bone and perio-dontal ligament remodelling. Progress should bemonitored clinically and radiographically. The initialforce applied to the root fragment should be used asa reference value and adjusted according to the rootmorphology and speed of extrusion.

The case we have described demonstrates that with amultidisciplinary approach to treatment, fracturesbelow the crest of the marginal bone can be treatedsuccessfully. The lateral incisor was extruded withmaterials available in many dental practices. Despitethe simplicity of the method, unwanted tipping, rotation or even contact of the extruding tooth withadjacent roots may result if the force is applied without regard to the centre of resistance of the rootfragment.


Prof. Adj. Osmar Aparecido CuoghiDisciplina de Ortodontia - Faculdade deOdontologia de Araçatuba – UNESPRua José Bonifácio 1193CEP 16015-050Araçatuba, SP BrazilTel: (+55 18) 3636 3236 Email: [email protected]

Figure 5. The final restoration.

Figure 6. Initial or pretreatment crown-root ratio 3:5 (a) and after the rehabilitation 3:4 (b). The crown–root lengths were measured on periapicalradiographs.

CUOGHI ET AL


References1. Turley PK, Crawford LB, Carrington KW. Traumatically

intruded teeth. Angle Orthod 1987;57:234–44.2. Olsburgh S, Jacoby T, Krejci I. Crown fracture in the per-

manent dentition: pulpal and restorative considerations.Dent Traumatol 2002;18:103–15.

3. Trushkowsky RD. Aesthetic, biologic and restorative consid-erations in coronal segment reattachment for fracturedtooth: a clinical report. J Prosthet Dent 1998;79:115–19.

4. Leroy RL, Asp JK, Raes FM, Martens LC, De Boever JA. Amultidisciplinary treatment approach to a complicated max-illary dental trauma: a case report. Endod Dent Traumatol2000;16:138–42.

5. Meiers JC, Freilich MA. Chairside prefabricated fiber-rein-forced resin composite fixed partial dentures. QuintessenceInt 2001;32:99–104.

6. Andreasen JO, Andreasen FM, Andersson L. Textbook andcolor atlas of traumatic injuries to the teeth, ed 4. Oxford :Blackwell Munksgaard, 2007: p 897.

7. Poi WR, Cardoso LC, Castro JC, Cintra LT, Gulinelli JL,Lazari JA. Multidisciplinary treatment approach for crownfracture and crown-root fracture: a case report. DentTraumatol 2007;23:51–5.

8. Villat C, Machtou P, Naulin-Ifi C. Multidisciplinaryapproach to the immediate aesthetic repair and long-termtreatment of an oblique crown-root fracture. DentTraumatol 2004;20:56–60.

9. Padbury A Jr, Eber R, Wang HL. Interactions between thegingiva and the margin of restorations. J Clin Periodontol2003;30:379–85.

10. Gargiulo AW, Wentz F, Orban B. Dimensions and relationsof the dentogingival junction in humans. J Periodontol1961;32:261–7.

11. Turgut MD, Gönül N, Altay N. Multiple complicatedcrown-root fractured of a permanent incisor. DentTraumatol 2004;20:288–92.

12. Bach N, Baylard JF, Voyer R. Orthodontic extrusion: perio-dontal considerations and applications. J Can Dent Assoc2004;70:775–80.

13. Ingber JS, Rose LF, Coslet JG. The biologic width – a con-cept in periodontics and restorative dentistry. AlphaOmegan 1977;70:62–5.

14. Berglundh T, Marinello CP, Lindhe J, Thilander B,Liljenberg B. Periodontal tissue reactions to orthodonticextrusion. An experimental study in the dog. J ClinPeriodontol 1991;18:330–6.

15. Ingber JS. Forced eruption: Part II. A method of treatingnonrestorable teeth – Periodontal and restorative consider-ations. J Periodontol 1976;47:203–16.

16. Sicher H, Du Brul EL. Anatomia Bucal. ed 8. São Paulo: Ed.Artes Médicas. 1991. p 511.

17. Sabri R. Crown lengthening by orthodontic extrusion.Principles and technics. J Periodontol 1989;8:197–204.

18. Minsk L. Orthodontic tooth extrusion as an adjunct of peri-odontal therapy. Compend Contin Educ Dent 2000;21:768–70,72,74.

19. Malmgren O, Malmgren B and Goldson L. Orthodonticmanagement of the traumatized dentition, In Andreasen JO,Andreasen FM, Andersson L. Textbook and Color Atlas ofTraumatic Injuries to the Teeth, 4th edn. Oxford: BlackwellMunksgaard, 2007, 669–715.

20. Reitan K. Principles of retention and avoidance of post-treatment relapse. Am J Orthod 1969;55:776–90.

21. Bondemark L, Kurol J, Hallonsten A, Andreasen JO.Attractive magnets for orthodontic extrusion of crown-rootfractured teeth. Am J Orthod Dentofacial Orthop 1997;112:187–93.

22. Pontoriero R, Celenza F Jr, Ricci G, Carnevale G. Rapidextrusion with fiber resection: a combined orthodontic-peri-odontic treatment modality. Int J Periodontics RestorativeDent 1987;7:30–43.

23. Lovdahl PE. Periodontal management and root extrusion oftraumatized teeth. Dent Clin North Am 1995;39:169–79.


Editorial

Dr Brian Lee thinks so. In a carefully executed studyDr Lee calculated the associations between the lengthsand areas of the roots of the permanent teeth andfound some remarkably high values. He reports thecorrelations were improved when the product oflength and width were used, and describes how to usehis data and to obtain optimal rates of tooth move-ment. This extensive study provides a wealth of datafor the clinician.

Decalcification around orthodontic attachments canbe distressing for patients and clinicians. According toDrs Uysal, Amasyali, Koyuturk, Ozcan and Sagdic,amorphous calcium phosphate-containing compositesreplace the mineral lost due to decalcification and maylessen the risk of decalcification in patients with poororal hygiene.

The cytotoxicities of separating elastics were investi-gated by Drs Pithon, Santos, Martins, Romanos andAraujo using neutral red over periods up to 168 hours.Both latex and non-latex separating elastics wereinvestigated and clinicians will be pleased to learnboth types were considered to be biocompatible.

In this latest study, Drs Miles and Weyant comparethe efficiencies of self-ligating and conventional por-celain brackets and report that the self-ligating brackets were quicker to ‘untie’ and ‘tie’ than con-ventional brackets and there were no significant dif-ferences in the alignment or discomfort experiencedby the subjects.

In a study of Brazilian subjects, Drs Motta, Souza,Bolognese, Guerra and Mucha report older Braziliansshow less of their upper incisors and more of theirlower incisors than young Brazilians. Some wouldargue that this is a good reason for the current concernabout maintaining lower incisor alignment.

Drs Kilic, Catal and Oktay provide norms for theMcNamara analysis for Turkish adolescents. Theyfound some small gender differences, but concludethat it may be possible to use the same norms for boysand girls.

In an electron microscopic study, Drs Bhalla, Good,McDonald, Sherriff and Cash confirm that the slot

sizes of six self-ligating brackets were larger than thestated dimension: in some cases by quite largeamounts. They caution that differences between slotwidths and archwire sizes may lead to significant lossof torque with some prescriptions.

Drs Dause, Cobourne and McDonald investigated thesensitivity and specificity of the Royal London SpacePlanning and Korkhaus analyses. They report bothanalyses were clinically sensitive, but the RoyalLondon Space Planning Analysis lacked specificity.Readers who are not familiar with these analyses willfind their article interesting and informative.

In an interesting study of indirectly applied cyclicloading and unloading to the inter-premaxillarysuture, Drs Uysal, Olmez, Amasyali, Karslioglu,Yoldas and Gunhan report that new bone was deposited in the expanded suture. They used twoloading cycles and report that the greatest percentageof new bone was found in the group subjected to thehigher loading cycle. Further studies will investigateadditional loading cycles and whether it is loading orunloading that is important for the formation of newbone.

In an EMG study of muscle activity in the upper lip,Dr Nihat Kilic confirmed that lip activity did notappear to determine the positions of the incisors. In aprospective clinical trial, Drs Pandis, Polychrono-poulou, Sifakakis, Makou and Eliades examine theeffects of levelling the curve of Spee on the mandib-ular incisors and arch widths. They report that about4 degrees of lower incisor proclination accompanied 1 mm of levelling with a straight-wire appliance.

Drs Ang and Dreyer compared the dental changesproduced by two advancement appliances used bypatients with obstructive sleep apnoea. Users of these appliances will be pleased to note that bothappliances had similar, mild effects on the dentitionand occlusion.

I was unaware that ozone water is used widely to dis-infect water systems until I read this article by DrsPithon and Santos. They report that ozone water didnot affect the bond strengths of the adhesives they

Can an optimal force be estimated?

used; a finding of interest to orthodontists andrestorative dentists using these materials.

When the skeletal changes in young Class III patientstreated with combined facemask and intermaxillarytraction were examined, Drs Thiesen, Fontes,Zastrow and May found that the most significantchanges occurred in the first three months of treatment.

The bond strengths of a number of different adhes-ives were not adversely affected when the same self-etching primer was used, according to Drs Scougall-Vilchis, Zarate-Diaz, Kusakabe and Yamamoto.

The final article in this issue is a case report by DrsCuoghi, Bosco, Mendonca, Tondelli and Miranda-Zamalloa of an incisor with a fractured root. Thetooth was extruded orthodontically and restored, following periodontal surgery. The authors point outthe advantages of a multidisciplinary approach totreatment of these challenging cases.

Michael Harkness

EDITORIAL



Current Therapy in Orthodontics

Authors: Ravindra Nanda and SunilKapilaPublisher: Mosby Elsevier(shop.elsevier.com.au)Price: AUD $236.00ISBN: 978 0323054607

This book has been prepared in honour of the signifi-cant contributions that Dr Ram Nanda has made toorthodontics throughout his 50 years in education. Itis seen as a collection of contemporary papers onnumerous relevant topics in orthodontics by a groupof professional colleagues who are seen as leaders intheir fields, and to a large extent, have shared theirprofessional development.

This book does not aim to outline the routine aspectsof diagnosis and treatment planning as seen in mosttextbooks in orthodontics, but focuses on some specific issues which make it compelling reading forthe experienced practitioner and graduate student.Unlike many textbooks in orthodontics, every chapterhas a unique focus with material that is generally contemporary in nature, leaving very little for thereader to gloss over.

The book is divided into four parts, based on issues in orthodontic diagnosis and treatment, clinical management of sagittal and vertical discrepancies,management of adult and complex cases and in Part 4,a glimpse into the future as to where the professionstands in embracing molecular techniques.

Part 1 introduces the reader to issues related to quali-ty of life and compliance. The outcome of contem-porary orthodontic treatment frequently includesissues relating to quality of life. In fact, many reviewsof publicly funded healthcare delivery systems nowrequire this to be considered in evaluating treatmentoutcome. These two chapters are thoughtfully pre-

pared and comprehensively referenced. Chapter 3demonstrates a method of cephalometric analysis,which challenges the orthodontist to simultaneouslyincorporate developmental status into the dynamics ofcraniofacial growth. Chapter 4 demonstrates how acomprehensive assessment of occlusal contact relationships may assist if developing treatment need, the outcome of treatment and how this mayrelate to orthodontic stability. Chapter 5 is an excel-lent chapter, which outlines the state of the art inthree-dimensional imaging to evaluate treatment out-comes. This provides an exciting view of what the clinician may anticipate in the future. Chapter 6 is acomprehensive outline of issues related to bonding ofappliances with a contemporary strategy to handlingwhite spot lesions. Chapters 7 and 8 provide a concisesummary of two excellent clinicians’ focuses in recentyears: Dr Sondhi on bracket placement and designand Dr Zachrisson on aesthetics and biomechanics.These chapters are excellent complements to theirpublications and lecture material.

Part 2 introduces the sagittal and vertical theme withChapter 9 presented by William Clark. This is anexcellent summary of Dr Clark’s twin block appliance,applying some of the significant research findings tohis own personal work. Chapters 10 and 11 present acomprehensive outline of the effectiveness of non-compliance Class II correctors. In Chapter 11, DrBowman comprehensively outlines how treatmentchoices may be based on the treatment objectives,moreover how appliance effects may be enhanced byincorporation of temporary anchorage devices.Chapter 12 gives a brief summary of maxillary deficiency in the transverse and antero-posteriorplanes. In Chapter 13 strategies to enhance protrac-tion, including supplemental temporary anchoragedevices and alternate expansion and contractionregimes to disarticulate the maxilla, are discussed.Chapter 14 is a brief overview of the physiology ofmastication and respiration and how this may relate tothe aetiology of open bites.

Chapters 15 and 16 outline biomechanical strategieswhich may be considered to address open bites and

Book reviews

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deep bites, based on differential diagnosis and devel-oping specific individualised goals.

Part 3 begins with a brief chapter demonstratingtreatment of patients with periodontal complications.It is followed by Chapter 18, which describes athought-provoking strategy to maintain midlinediastema closure with creative positioning of theteeth. Chapter 19 outlines complex goal-orientedbiomechanics to manage some challenging clinicalsituations in adults. Chapter 20 discusses the subjectof sleep apnoea and the role of the orthodontist inboth non-surgical and surgical management of thisproblem, as orthodontists increasingly receive referrals for this serious condition. Chapter 21 focuses on the management of the worn dentitionand provides an overview of interdisciplinary plan-ning to achieve optimal results. Chapters 22 to 24focus on temporary anchorage appliances, their indi-cations, placement and biomechanical application.These excellent chapters will facilitate the com-prehension of how these adjuncts may be used effec-tively. The objective of decreasing treatment time isthe focus of many clinicians’ research; distraction ofthe canine was introduced nearly a decade ago andnumerous physical, chemical and surgical strategieshave been suggested. Chapter 25 outlines the technique,which on the surface appears quite challenging, but ithas provoked further developments in this field.

Part 4 begins with chapters that are well-written andeasy to comprehend on the biological mechanisms intooth movement. Comprehension of these pathwayshas opened the door to understanding how cliniciansmay improve treatment effectiveness without unde-sirable consequences such as root resorption. A finalchapter outlines the future of tissue engineering; asclinicians become more enthusiastic of the impactthat these procedures will have on contemporarymedicine.

Drs Ravindra Nanda and Kapila should be congratu-lated on establishing such a collaborative effort toproduce a state of the art book. In summary, thisbook is clinically focussed with extensive illustrationswith particular emphasis on biomechanics, as youwould expect from Drs Nanda and Kapila. This bookupdates many new exciting developments in ortho-dontics. It should grace the personal libraries of allgraduate students and practising orthodontists.

Mithran Goonewardene

Self-Ligation in Orthodontics

Authors: Theodore Eliades and NikolaosPandisPublisher: Wiley-Blackwell, 2009(www.wiley.com)Price: AUD $170.00ISBN: 9781405181907

Clinical orthodontics has been inundated with dis-cussion, promotion, hype and controversy about self-ligating brackets for the past 10 years or so.Extraordinary claims have been made that a little clipor slide instead of a piece of wire or elastomeric ringcan reduce the need for surgery, extractions, expan-sion devices etc. Other claims of faster treatment, lessdiscomfort, better hygiene, less root resorption makethese brackets seem highly desirable. If these claimsare true, the much higher price paid for them wouldbe worth it.

Orthodontists with a healthy skepticism about claimsmade for more expensive products than they cur-rently use are right to want high quality evidence tosupport the various claims. Even if all the claimsmade are not substantiated, perhaps there are somereal advantages in using the brackets that would maketheir use beneficial. Here is a text book that may provide the answers to those considering using self-ligating brackets, or seeking to know how to use themmore efficiently.

The authors’ preface notes the hype around thebrackets, with the industry organising conferencesand pushing an agenda. This has resulted in ‘state-ments and claims which contradict fundamentalprinciples of mechanics and craniofacial biology,actually doing an injustice to a bright idea for a newappliance’. The stated aim of this book is to ‘compre-hensively review self-ligation and summarise the evi-dence available in the literature’. There are indeedmany references right up to publication date quotedat the end of each chapter.

There are also many chapters of background textswritten by eminent scholars. These cover bracketmaterial properties, essentials of clinical researchdesign, molecular response of periodontal ligament


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and bone to loading, root resorption, and attachmentof oral microbiota to dental surfaces. These back-ground chapters are quite detailed and relate to dentistry and oral biology in general, not specificallyto self-ligating brackets. These chapters occupy aboutone third of the book and can act as a refresher orupdate on the basic topics. However, to get fullunderstanding, some of the chapters would requiresignificant extra study by any clinicians who havebeen out of dental school a few years.

The book starts with a review of the development andevolution of light force and self-ligating orthodontics.There is a listing of the various brackets available atthe time of publication, and a brief review of some ofthe features of the most well-known brackets. Thereis some discussion of the active and passive bracketconcept. A more comprehensive description andcomparison of the features of the main brackets onthe market would give the reader a better under-standing and ability to evaluate which bracket mightsuit his or her practice.

The short chapter on the biomechanics of self-ligation describes some of the authors’ laboratorystudies the forces generated on regular and differentself-ligating brackets. Some predictable differencesare found between the various brackets in forcesapplied in different planes of space. For instance, passive self-ligating brackets with a rigid closingmechanism deliver higher forces to the tooth inbucco-lingual and rotational movements than dobrackets with active spring clips or elastomeric ties.There is discussion about the loss of stiffness that has been reported in the spring clips of the activebrackets, In-Ovation R, but not Speed. The authorssay that ‘the performance and aging of the nickel-titanium clips significantly depend on the alloy com-position and the associated phase transformations’. Infact, the clip on the In-Ovation bracket is cobalt-chrome and only the Speed is nickel-titanium.

The final chapter on treatment mechanics with self-ligating brackets is where the reader would be lookingfor tips and ideas for using the advantages of self-ligating brackets to improve treatment progress andoutcomes. Instead, the chapter is a brief and basicprimer on orthodontic diagnosis, treatment planning,mechanics and retention, with only a couple of pointsabout doing things differently with self-ligatingbrackets. There is no discussion of the better rota-tional control we see when using sliding mechanics,

different anchorage setups that can be used due tolower forces required in retraction, or the use of specially designed archwires to complement theaction of the spring clips.

In short, if you are looking for a book that gives acomprehensive overview of the features and possibili-ties of the different self-ligating brackets, along withthe most efficient ways to use them, you will need tolook elsewhere.

Paul Schneider

Minor Tooth Movement with Microimplantsfor Prosthetic Treatment

Author: Hyo-Sang ParkPublisher: Dentos Australia Pty LtdEmail: [email protected]: AUD $200.00ISBN: 978 89 956605 4 6

This hard covered book is published by Dentos CoLtd., manufacturers of the micro-implants used bythe author. The book is well laid-out with high quality photographs and illustrations in all sections.The original text was presumably written in Koreanand has been translated into English. This has theeffect of confronting the reader with occasional, oftendistracting, errors of expression.

The book is divided into seven chapters. The first chapter describes the surgical procedure recom-mended by Dr Park. It is a detailed description oftechnique, also discussing the pros and cons of self-tapping and self-drilling micro-implants. The anatomical considerations in the selection ofimplant sites are described and a brief section oncomplications is included.

The second chapter is on molar uprighting. Theextrusive side effects of molar uprighting are dis-cussed, along with options for micro-implant place-ment to control the vertical effects. The concept ofindirect anchorage, where the implant is attached toanchor teeth that are then used to place load on thetarget tooth or teeth, is introduced in this section. Aninteresting innovation described is the use of two

BOOK REVIEWS


adjacent micro-implants to increase stability. Severalcases are presented to illustrate the techniques discussed.

The next chapter, the largest, is on molar intrusion.Several case reports are used to describe methods forintruding various teeth and combinations of teeth.These include maintaining the vertical position ofteeth after the loss of opposing teeth, and intrusion ofone and two maxillary molars. The use of a combina-tion of buccal and palatal micro-implants is shown,along with a strategy to control the transverse sideeffects of intrusion. The intrusion of mandibularmolars is briefly described, including the difficultyexperienced because of the inability to placemandibular lingual micro-implants.

The fourth chapter describes the protraction ofmolars; the mandibular and maxillary molars dis-cussed separately. Micro-implant placement optionsare described with clinical examples. In some casesindirect anchorage was used. For direct protraction anorthodontic bracket was attached to adjacent micro-implants with a sectional archwire.

The next section describes forced eruption. Twointeresting cases are described: one using twin micro-implants with an orthodontic bracket and archwire toextrude a fractured maxillary canine, and the other toextrude a fractured upper central incisor. Both casesare described and illustrated with radiographs andphotographs. A palatally impacted canine case is adequately managed, using the same technique.

A short penultimate chapter discusses the redistri-bution of space for dental prostheses.

The final chapter discusses the ‘nuts and bolts’ ofmicro-implants including such topics as success rates,complications, force levels, osseointegration and solu-tions when initial stability is not obtained. This book,while being the opinion of a single author, has valuebecause of Dr Park’s extensive experience with theseadjuncts. Each section has a reasonable number ofreferences, mostly from recent publications. The illustrations are of a very high quality, making thedescription of techniques easy to understand.

While the title of the book suggests a focus on pros-thetic treatment, it can be considered a usefulresource for all orthodontists using micro-implantsfor any purpose.

Joe Geenty

Dental Practice: Get in the Game

Editor: Michael Okuji Publisher: Quintessence Books 2010(www.quintpub.com)Price: USD $48.00ISBN: 978 0 86715 492 4

Dr Okuji has edited a book which attempts to fill awell-known gap in dental undergraduate education –understanding the business environment and settingup or buying a practice and getting that first job. AndI would have to say this is an excellent publication forthat purpose.

Like many textbooks with chapters by different con-tributors, this book is very good in parts. There are 10chapters that cover everything from ‘Choosing a Path’through to business plans and valuation methods,with some useful appendices. The chapters that workless well, particularly for Australian dentists, includethe ones on dental practice regulations, managed careand insuring your practice. This is predominantlybecause of the large differences in legislation andbusiness regulations.

A few other chapters work less well also, but for dif-ferent reasons. The chapter on communications is notlong enough to develop adequately – with only onereference to Dr Coveys' celebrated ‘Seven habits ofhighly effective people’. But I imagine that only somuch can be presented in a single book covering sucha large area of interest. More references would havehelped the reader explore these areas. Chapter 7, onunderstanding basic finances is perhaps the opposite,with many pages devoted to this and the introductionof some complex concepts from corporate financesuch as net present value, which while important,might be a stumbling block for young dentists. There is a necessarily long section on taxation forUSA residents.

However, the other chapters more than make up forthese small deficiencies. Chapter 1 is an excellentstructured guide for the young dentist on how todecide which way to go. It has many break-out boxesof anecdotes and advice and these alone would beworthwhile for young general or specialist dentists.


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The chapters on finding a job, purchasing a practiceand starting a new practice are excellent.

Dr Okuji has edited and written a very good referencebook for younger dentists to read about their practicefuture. I hope that such a book is used in the under-graduate curriculum here and the USA.

Brad Wright

Introduction of Innovative OrthodonticConcepts Using Microimplant Anchorage

Author: Haruyuki HayashiPublisher: Dentos Australia Pty LtdEmail: [email protected]: AUD $75.00ISBN: 978 89 956605 2 2

This 75-page booklet has been translated into English(except for the bibliography!), but it is easy-to-readand well-illustrated, making for a short read also.

The introduction is dated August 2006 and indicatesthat Dr Hayashi has been involved in micro-implantanchorage for more than 15 years. The aim of thepublication is to address possible uses of micro-implant anchorage for minor tooth movements tofacilitate oral rehabilitation without involving full-bracketed orthodontic appliances. It is primarilydirected at the general practitioner or restorative spe-cialist, but certainly offers some innovative andthought provoking ideas as suggested by the title.There are apparently further publications by theauthor addressing more complex and specific issues,either planned or in print.

Technical issues of placement and minimising andovercoming problems are dealt with at the end of thetext, also offering some handy tips. However, in whatis a rapidly growing and evolving area of clinical practice there are possibly some superseded con-cepts, most notably the suggested timing of loadingin relation to placement.

Overall, this booklet is a worthwhile stimulus fordevising relatively simple solutions for problems toaid oral restoration, but it may not offer much that istruly new to the orthodontist who has taken an inter-est in the use and application of micro-implants(miniscrews, TADS) over recent years.

Steven Langford


Impaction and retention of second molars:diagnosis, treatment and outcome. A retrospective follow-up study

C. Magnusson and H. Kjellberg

Failure of tooth eruption or tooth impaction is a com-mon problem affecting 20 per cent of the population.While the incidence of second molar impaction is low,knowledge regarding the aetiology is largely based oncase reports and a few clinical studies. The treatmentof these teeth often requires a multidisciplinaryapproach and interdisciplinary discussion in decidingthe best treatment plan. The authors aimed todescribe the outcome of treatment in patients experi-encing second molar impaction and to report the out-come of no treatment.The retrospective, longitudinal follow-up study iden-tified after exclusion, 87 patients (42 males, 45females) with a mean age of 15 years and with 166impacted second molars. One hundred and eight ofthe second molars were treated, of which 79 were fol-lowed over periods ranging from 1 to 5 years. Theimpacted molars were diagnosed from CT scans,panoramic or periapical radiographs. Study casts andphotographs were used to assess other parametersrelated to the occlusion. The outcome of treatmentand the outcome of no treatment was assessed, withtreatment designated a failure if the impacted secondmolar did not erupt 12 months after surgical inter-vention. If a second molar was extracted, success wasdefined by the acceptable eruption and position of thethird molar.Of the diagnosed impacted second molars, 80 per centwere either orthodontically or surgically treated and,of those, less than half erupted into a proper position.Of the 20 per cent which remained untreated, slightlyfewer than half erupted favourably. The most success-ful form of treatment was the surgical exposure of theimpacted molar and the least successful treatmentused the third molar to replace the second molar

following its extraction. The authors concluded thatno matter what the treatment, success could not beassured, but surgical exposure offered the best option.Unfortunately, the severity of the impactions was notdetailed and so a solid and reliable conclusionbecomes more difficult. The clinical experience of thereviewer indicates that the more vertical theimpaction, the more likelihood of success, and themore horizontal the second molar impaction, themore problematic the management. The article wouldhave been improved by an indication of the severity of the impaction and its relationship with treatmentoutcome.

Angle Orthodontist 2009; 79: 422-427

Exposure of unerupted palatal canines: asurvey of current practice in the United Kingdom and experience of a gingival-sparing procedure

H.R. Spencer, R. Ramsey, S. Ponduri and P.A. Brennan

There is argument regarding the best surgical pro-cedure for the exposure of palatally impacted canines.Surgical exposure may either be open or closeddepending on diagnostic needs, but there has beenreported surgical variation among operators. In orderto determine the current practice in the UK, a ques-tionnaire was sent to consultant oral and maxillofacialsurgeons. The questionnaire described pictorially, fourdifferent exposure procedures and respondents wereasked to indicate which surgical procedure they usedand preferred.The four procedures were:1. A full thickness palatal mucoperiosteal flap withexcision of a wedge of tissue over the uneruptedcanine to the gingival margin of the flap, prior to itsreplacement.2. A full thickness flap as before, but with only a window of tissue removed over the unerupted canine.

Recentpublications

Abstracts of recently published papers reviewed by the Assistant Editor, Craig Dreyer


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3. A gingival-sparing approach involving the removalof tissue over the crown of the unerupted canine andthe application of a periodontal dressing.4. A full thickness palatal gingival margin flap and thebonding of an orthodontic attachment with goldchain affixed. The flap is subsequently replaced with-out the excision of any soft tissue (closed exposure).The respondents had an opportunity to annotatetheir preferred procedure if the above four were notpractised. There were 343 replies to 565 question-naires and, as expected, there was extreme variationamong the surgeons. Two-thirds of the respondentsonly performed one procedure, either 1 (wedge excis-ion) or 4 (closed exposure). Half of the respondentsincluded procedure 4 as one of the techniquesemployed. Seventy-one per cent included the openprocedure as a preferred technique. Only 9 per centof respondents avoided the gingival margin of theadjacent teeth during the canine exposure. Neverthe-less, the authors recommended procedure 3 as the tis-sue-sparing technique of choice. The premise of thetechnique was that the canine would erupt sponta-neously after the removal of the overlying tissues. Thetechnique was quick and minimally invasive but itwas noted, with concern, that the technique was usedby so few.

British Journal of Oral and Maxillofacial Surgery 2009: doi: 10.1016/j.boms.2009.08.032

Diagnostic predictability of digital versusconventional panoramic radiographs in thepresurgical evaluation of impactedmandibular third molars

E. Ferrús-Torres, J. Gargallo-Albiol, L. Berini-Aytés and C. Gay-Escoda

To date, panoramic radiographs are the most widelyused radiological diagnostic technique in dentistry.There are several limitations with this two-dimen-sional approach to diagnosis, which often necessitatesthe use of complementary films. With improvementsand the advent of digital radiology, conventionalpanoramic radiology is being replaced, but questionsremain regarding the diagnostic quality of digitalimages. The authors designed a prospective study tocompare the diagnostic predictability of conventionalpanoramic radiographs with digital radiographs inthe presurgical assessment of impacted third molars.The study assessed 287 patients (125 males, 162

females) with 390 impacted third molars referred forsurgical removal. The molars were in submucosalpositions, either partially or totally impacted in bone.Root formation had been completed, there was noassociated pathology and patients with uncontrolledsystemic disease or local infection were excluded.The position, morphology and surgical techniquewere recorded on 84 molars assessed by digitalpanoramic radiographs and 306 molars assessed byconventional panoramic radiography. Four assessorsof varying experience compared the presurgical datawith the surgical findings and established diagnosticprecision. There were statistically significant benefitsand precision in using the digital radiographs forpresurgical evaluation of the third molars. The conventional panoramic film distorted the positionand morphology of the molar, which affected thepresurgical strategy of the less experienced surgeons. Surgeon experience had a profound influence ondiagnostic planning. It was concluded that digitalpanoramic radiography offered significantly greater diagnostic advantages over conventional radiography.

International Journal of Oral Maxillofacial Surgery 2009; 38:1184–1187

A review of the diagnosis and managementof impacted maxillary canines

M.M. Bedoya and J.H. Park

This article is a literature review which deals with theclinical and radiographic diagnosis of impacted max-illary canines. In addition, the authors searched theliterature to determine the types of interceptive treat-ment (surgical and orthodontic) used to prevent ortreat canine impaction. The literature was gatheredfrom clinical and radiographic studies as well as casereports, and only studies pertaining to the prevalence,aetiology and diagnosis of impacted canines wereselected. Included were the most recently publishedarticles, which described the orthodontic and surgicaltechniques of management.The review covers in overview, the incidence, possibleaetiology and sequelae of canine impaction as well asthe clinical and radiographic diagnostic proceduresinvolved in management. Interceptive treatment isexplored and limited to deciduous canine extractionwhile the orthodontic and surgical management isdescribed more comprehensively. However, there is

RECENT PUBLICATIONS


little about the significant treatment difficulties thatmay arise and this, given that the review has beenwritten for general practitioners, is hardly surprising.The authors conclude that impacted canines are acommon occurrence that is best managed by earlydetection and timely interception. The commontreatment of surgical exposure and orthodontic eleva-tion to guide the canine into place is an over-simpli-fication of management and denies the problems anddifficulties that often arise.

Journal of the American Dental Association 2009; 140: 1485-1493

Wisdom teeth: mankind’s future third vice-teeth?

D-H. Zou, J. Zhao, W-H. Ding, L-G. Xia, X-Q. Jang andY-L. Huang

The science of tissue engineering has proven to beuseful for dental tissue and whole-tooth regenerationstrategies. The recent identification of postnatal dentalstem cell populations suggests that bioengineeringapproaches may be used to regenerate a variety ofdental tissues and even entire teeth, provided that anappropriate seed cell is identified. Autologous toothgerm cells are multipotent stem cells that have thecapability of differentiating into ameloblasts, odonto-blasts, cementoblasts and alveolar bone providingalmost any tooth tissue. The authors identified thatthird molars might be extracted for a variety of reasons and provide a strategy for the replacement ofpermanent teeth in later life by the prior harvesting ofthird molar stem cells. The concept involves the salvaging of germ cells from a young patient whose third molars are in the early stages of develop-ment. The extracted tooth germ is cryopreserved inliquid nitrogen and an electronic database of materialestablished and maintained. In later life at a time oftooth loss, the patient’s tooth germ cells may belocated and multipotentiality identified, to produce atooth with specific characteristics to the tooth requir-ing replacement. The addition of growth factors andscaffold materials would guide the formation of thenew tooth as it is seeded in an intra-arch space.The authors reveal how successful innovations indentistry may be guided by advances in basic researchand close partnerships between researchers and clini-cians. This article heralds a dental future that is notthat far distant provided philosophical and ethicalconsiderations can be overcome.

Medical Hypotheses 2010; 74: 52-55

Orthodontic management of a patient withimpacted and transposed mandibularcanines

R.C. Almeida, F.A.R. Carvalho, M.O.A. Almeida and J. Jr Capelli

Ectopically erupting and impacted canines may befound in transposition with neighbouring teeth. Theauthors of this article provide a case report ofimpaction of both mandibular canines with theiradjacent lateral incisors. The patient was a 10 year-old female with good facial proportions and a Class Ibimaxillary protruded malocclusion. Radiographi-cally, both lower permanent canines were impactedbetween the central and lateral incisors and the lowerright second premolar was extremely hypoplastic andunerupted. The treatment aims were to improve thepatient’s dental appearance by creating space for theunerupted canines. This initially occurred by theplacement of coil springs bilaterally between the incisors using fixed appliances supported by a lingualarch. Even though there was some space distal to thelateral incisors, it became apparent that additionalspace would be required. This was created by theextraction of the lower left lateral incisor which leftthe patient, at deband, with Class I buccal segments,a ‘normal’ overbite and overjet and dental midlinesthat did not coincide. The upper arch was simplyaligned. The authors achieved a satisfactory result andindicated that transpositions often should not be corrected from a cost-benefit viewpoint.

Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology andEndodontics

2009;08:e26-e32

Assessment of the associated symptoms,pathologies, positions and angulations ofbilateral occurring mandibular third molars:is there any similarity?

Z.Z. Akarslan and C. Kocabay

As the most common dental impaction, an in-completely erupted third molar often gives rise tosymptoms and pathologies, including pericoronitis,pain, swelling, distal caries, bone loss and many others. The eruption status, position and angulationof the tooth reportedly have an impact on thesesymptoms. The aim of the article was to evaluate andestablish possible similarities between associatedsymptoms, pathologies, position and angulationtypes on bilaterally occurring mandibular thirdmolars in young adult patients.


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Clinical and radiographic examinations were per-formed on 342 patients (167 females, 175 males)aged between 20-25 years (Mean: 22.2, SD: 1.8).Eruption status, mucosal and bony coverage type,presence of pain, pericoronitis, suppuration, ulcer-ation, caries, bone loss, root resorption, cyst ortumour formation was investigated and recorded.Patients having one completely or partially eruptedmandibular third molar were classified as Group 1while patients with bilaterally impacted mandibularthird molars were placed in Group 2.No significant difference was found between thesymptoms and pathologies related to the mandibularright and left third molars among both groups andgenders. In addition, no significant difference wasfound between the right and left mandibular molarsin the assessment of mucosal coverage type, bonycoverage type and position in either group. However,gender had an influence on bony coverage type and

ramus distance of both molars in Group 2. This wasascribed to a difference in the size and anatomy of themandible in females. In the total sample, symmetrywas present for horizontal or distoangular, and ver-tical or distoangular angulations in Group 1 andGroup 2. Gender was also found to have an influenceon angulation symmetry. The authors concluded thatsimilarity was evident between the symptoms andpathologies related to bilaterally impacted thirdmolars; however, symmetry in position and angula-tion differed according to eruption status, angulationtype and gender. It was concluded that this infor-mation provided assistance to surgeons in their evaluation of third molars for extraction.

World Journal of Orthodontics 2009; 10:345-349


Interproximal diamond stripsOrtho Technology’s newrange of perforated inter-proximal diamond strips aredesigned for interproximalstripping, shaping and con-touring. According to the

manufacturer, the perforated strips are more flexible than solidstrips and provide better visibility and control. The strips arecolour-coded and available in two widths, narrow and wide. For more information on the range of interproximal strips, diamond burs and diamond discs, contact Ortho TechnologyPty Limited.Freecall: 1800 678 407Website: www.orthotechnology.com

InVu aesthetic brackets with Readi-Base pre-applied adhesiveInVu aesthetic brackets by TPOrthodontics have colour-match-ing technology that enables thebrackets to blend with individualteeth, and a pre-applied adhesivefor easy application. The latter isclaimed to reduce chair-time andprevent brackets from drifting during placement. According to the manufacturer, the brackets are robust, have excellent aesthetics, low friction and debond easily.For further information contact TP OrthodonticsTel: 1800 643 055Email: [email protected]

topsCephMate digitising softwareThis software allows the userto quickly place cephalometriclandmarks, trace, analyse,measure and perform STOand VTO simulations in a single window. Key featuresinclude the ability to adjustlandmarks without re-digitising

and realistic, live soft tissue morphing. CephMate works withany X-ray imaging software or digital camera.For further information contact topsOrthoEmail: [email protected]: www.topsOrtho.com

topsOrtho practice management softwaretopsOrtho is a Mac OS X prac-tice management programmedesigned by a practising ortho-dontist. The programme includesall necessary software: practicemanagement, imaging, wordprocessing, backup software and a SQL database. Just oneserver at a main office also serves satellite offices, with noimpact on speed.For further information contact topsOrthoEmail: [email protected]: www.topsOrtho.com

Damon Clear Bracket Ormco’s new Damon Clear bracketsare polycrystalline alumina brackets.They are impervious to staining anddiscolouration, combine the low-friction properties of passive self-lig-ation technology and have goodaesthetics, according to the manu-

facturer. They provide full rotation control and the Spin-Tek slidefacilitates fast, comfortable wire changes and adjustments.For further information contact Ormco Pty LimitedTel: 1800 023 603 or your Ormco Territory Manager

Clear Debonding Tool The New Damon Clear Debond-ing Tool from Ormco enablesquick, pain-free debonding of theDamon Clear bracket, ac-cordingto the manufacturer. The wedgeof the instrument is positioned onthe occlusal side of the bracketand the instrument jaws placedbehind the gingival and occlusaltie wings. When the instrumenthandle is squeezed, the wedgeengages the crown and thebracket peeled from the tooth.For further information contact Ormco Pty LimitedTel: 1800 023 603 or your Ormco Territory Manager

New products

New products are presented as a service to our readers, andin no way imply endorsement by the Australian OrthodonticJournal.

Australian Orthodontic Journal Volume 26 No.1 May 2010 107

2010June 15-1986th Congress of the European Orthodontic Society, St.Bernardin Adriatic Resort and Convention Centre, Portoroz,Slovenia.Website: www.eos.2010.siEmail: [email protected]

June 30 – July 3New Zealand Association of Orthodontists’ Biennial Conference,Hotel Grand Chancellor, Christchurch, New Zealand.Website: www.conference.co.nz

July 1-34th Bali Orthodontic Conference and Exhibition, The AyodyaResort, Nusa Dua, Bali.Website: www.boce5.ikorti-iao.orgEmail: [email protected]

July 8-11European Society of Lingual Orthodontics Congress, QueenElizabeth II Conference Centre, Westminster, London.Website: www.eslo-congress.com

August 2-3Association of Philippine Orthodontists’ 7th Biennial NationalOrthodontic Congress, Hotel InterContinental Manila, MakatiCity, The Philippines.Website: www.apo.com.ph

August 18-21XIII International Orthodontic Congress of the Chilean OrthodonticSociety, Centro de Eventos Casa Piedra, Santiago, Chile.Website: www.sociedadortodonciachile.orgEmail: [email protected]

September 18-21British Orthodontic Society Conference, Brighton, United Kingdom.Website: www.bos.org.uk

September 20-22South African Society of Orthodontists Conference, NewlandsConference Centre, Cape Town, South Africa.Website: www.saso.co.za

September 23-2562nd Annual Scientific Session of the Canadian Association ofOrthodontists, Whistler, British Columbia, Canada.Website: www.cao-aco.org

November 25-27Societa Italiana di Ortodonzia’s 22nd International Congress,Florence, Italy.Website: www.sido.it

December 11-12Taiwan Association of Orthodontists’ 2nd World and 9th AsianImplant Orthodontic Conference, Taipei International CenventionCenter, Taipei, Taiwan.Website: www.wioc2010.org.twEmail: [email protected]

December 17-19Indian Orthodontic Society’s 34th Indian Orthodontic Conference,Mangalore, India.Website: www.iosweb.netEmail: [email protected]

2011March 4-6Australian Society of Orthodontists’ Foundation for Research andEducation Meeting, Melbourne, Australia.Website: www.aso.org.au

June 19-2387th Congress of the European Orthodontic Society, Istanbul,Turkey.Website: www.eso2011.com

2012February 11-1423rd Australian Orthodontic Congress, Perth, Western Australia,Australia.Website: aso2012perth.com

November 23-268th Asian Pacific Orthodontic Society and the 8th Asian PacificOrthodontic Conference, New Delhi, India.Website: www.iosweb.net

Orthodontic calendar

For a list of meetings and links to websites of national and international orthodontic societies, visit the World Federation of Orthodontics, www.wfo.orgFor inclusion in the Australian Orthodontic Journal please contact: Dr Tony Collett Tel: (+61 3) 9756 0519Email: [email protected]


Australian Society of OrthodontistsSecretariatPO Box 576, Crows Nest, NSW 1585

ASO Federal Council

PresidentMike Razza: [email protected]

Vice PresidentSteven Langford: [email protected]

SecretaryCarl Sim: [email protected]

TreasurerCrofton Daniels: [email protected]

Secretary-ElectAndrew Toms: [email protected]

Treasurer-ElectSimon Freezer: [email protected]

CouncillorsPeter Lewis: [email protected] Hannan: [email protected] Collett: [email protected]

Presidents and Secretaries of ASO State BranchesNew South WalesPresident: Stephen Duncan: [email protected]: Stephen Moate:[email protected]

VictoriaPresident: Tracey Shell: [email protected]: Kylie Moseling: [email protected]

QueenslandPresident: Grant Hamilton-Ritchie: [email protected]: Claylia Ward: [email protected]

South AustraliaPresident: Jonathan Ashworth: [email protected]: Darren Di Iulio:[email protected]

Western AustraliaPresident: Fiona Hall: [email protected]: Kevin Murphy: [email protected]

ASO Committees 2010-2012Appeal CommitteeChairman: Craig [email protected]

Archival CommitteeArchivist: Grant [email protected]

Australasian Orthodontic BoardChairman: Stephen [email protected]

Journal CommitteeEditor: Michael [email protected]

Awards CommitteeChairman: David [email protected]

Cleft Lip and Palate Reference CommitteeChairman: Kit [email protected]

Communications and Information CommitteeChairman: Stephen [email protected]

23rd Congress Organising Committee (2012)Chairman: Howard [email protected]

24th Congress Organising Committee (2014)Chairman: Marie [email protected]

Constitution CommitteeChairman: John [email protected]

Education/Membership Advisory CommitteeChairman: Mithran [email protected]

Foundation for Research and EducationChairman: John [email protected]

Orthodontic Services CommitteeChairman: Tony [email protected]

Give a Smile CommitteeChairman: T. [email protected]

Communications and Information committeeChairman: Ronda [email protected]

Recent Graduates CommitteeChairman: Matthew [email protected]

Chairmen/Heads of Academic DepartmentsUniversity of AdelaideProfessor Wayne [email protected]

University of MelbourneTBA

University of QueenslandDr Shazia [email protected]

University of SydneyProfessor M. Ali [email protected]

University of Western AustraliaAssociate Professor M. [email protected]

Allied AssociationsAustralian Dental AssociationFederal Secretariat: Executive Director, Neil Hewsonwww.ada.org.au

World Federation of OrthodontistsPresident: Athanasios E. Athanasiouwww.wfo.org

New Zealand Association of OrthodontistsPresident: P. [email protected]

Directory

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Revista Australiana de Ortodoncia (1)

Documents

Transcript of Revista Australiana de Ortodoncia (1)