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EGYPTIANDENTAL JOURNAL

Vol. 59, 2357:2366, July, 2013

THE EFFECT OF BURSTONE’S INTRUSIVE MECHANICS ON THE SMILE OF NON-GROWING FEMALES

ABSTRACT

A smile is considered a “gummy smile” if a significant amount of gingival tissue can be seen as a person smiles. Although a gummy smile is considered a normal variation of human anatomy, many people with gummy smiles are very self-conscious when smiling. The aim of the present study was to interpret the effect of Burstone’s intrusion mechanics on the smile of non-growing female patients. The sample in this study consisted of nine non-growing female patients with age range 18-25 years having deep bite and gummy smile, and treated with Burstone’s intrusive mechanics. The results were obtained after two months, and the deep bite and gummy smile were improved, in other wards the deep bite was reduced and the amount of gum tissue appearing on smiling was also reduced.it was concluded that Burstone’s mechanics are effective in treatment of gummy smile.

KEY WORDS: Gummy smile, Burstone’s intrusive technique, deep bite.

Suzan A. Marzouk*; Hisham A. Afifi* and Manal Y. Foda*

* Orthodontic Department, Faculty of Oral and Dental Medicine, Cairo University

INTRODUCTION

Life style, image and confidence are all in the smile. Appealing smile directly depends upon the relation existing between teeth and lips. Gummy smile can have a negative effect on the esthetics of a smile, so it should be treated by: Surgical contouring of the gum tissue or gingivectomy, same-day laser treatment, surgical lip repositioning, orthodontic treatment to move the teeth to more suitable position (intrusion, especially in deep bite cases), or combination of orthodontic treatment (intrusion) and surgical contouring (Durgekar and

Naik, 2010).

Deep bite is a term applied when there is excessive vertical overlap of the incisors. It can be treated by removable appliances or fixed mechanics as continuous arch bar wires with an accentuated curve of spee, Burstone segmented arch, utility arch or class II elastics as an extra-oral appliances (Foda, 1998).

The aim of the present study was to interpret the effect of Burstone’s intrusion mechanics on the smile of non-growing female patients.

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SUBJECTS AND METHODS

The sample in this study consisted of nine non growing female patients with age range 18-25 years. The criteria of selection were: Class II division 1 patients with minimal crowding, gummy smile, deep over bite, skeletal class I, absence of any gingival inflammation, no previous orthodontic, prosthodontic treatment, maxillofacial or plastic surgery, no significant medical history, no history of trauma, and permanent incisors, canines, premolars, first and second molars were fully erupted.

The following records were taken before and after complete successful bite opening for all the selected subjects: (1) Patient chart, (2) Study casts, (3) Extraoral radiographs (lateral cephalometric and panoramic radiographs), (4) Intraoral radiographs and (5) photographs.

Extraoral radiographs

A) Lateral cephalometric radiographs

Preoperative and postoperative lateral cephalometric radiographs were taken to interpret hard, dental and soft tissue changes.

1) Incisor changes:

a- Intrusion: (Root center-PP and Root center-MP)

b- Tipping: (U1/PP and L1/MP)

c- Position: (Is-NV and Ii-NV)

d- Length: (U1 and L1 Lengths)

2) First molar changes:

a- Extrusion: (Bifurcation-PP and Bifurcation-MP)

b- Tipping: (U6/PP and L6/MP)

c- Position: (U6-PTV and L6-PTV)

d- Length: (U6 and L6 lengths)

3) Changes in jaw relation: (SN/MP, ANB°, AB difference-NV, SNA°, A-NV, SNB°, B-NV and Y-axis angle).

4) Soft tissue changes

a. Lip length: [UL length (Sn-U Stm) and LL length (Si-L Stm)]

b. Lip competency (inter-labial gap): U Stm-L Stm

c. Lip position: [UL position (LS-EL) and LL position (Li-EL)]

d. Soft tissue profile: G` Sn Pg` angle

e. Lip thickness: [UL thickness (LS-IS) and LL thickness (Li-Ii)]

B) Panoramic radiographs: to evaluate the root and bone conditions.

Intraoral radiographs:

Preoperative and postoperative periapical radiographs were taken to assess changes in the root length and/or apical contour of the maxillary anterior teeth.

Photographs:

High quality digital images for each patient were taken before and after bite opening at smile and rest positions. The subjects were instructed to hold their heads in natural head position by looking straight to an imaginary mirror. The camera lens was subjected to be parallel to the apparent occlusal plane. Included in the capture area (frame) were two rulers with millimeter markings. The rulers were secured in a cross configuration so that if the subject accidentally rotated 1 ruler, the other could be used to analyze the frame. The reference ruler was used to calculate the magnification (or reduction) factor which was in turn used to calculate the real distance by dividing the obtained distance from the software ruler tool by the magnification (or reduction) ratio (Mittal et al., 2009). In photoshop software, the following data were measured and entered into Excel spread sheet (Microsoft).

THE EFFECT OF BURSTONE’S INTRUSIVE MECHANICS (2359)

- Upper lip length: distance from subnasale to stomion superius

- Upper lip thickness: vertical distance from the most superior point of the cupid’s bow to the most inferior portion of the tubercle of the upper lip.

- Interlabial gap: distance between upper and lower lips.

- Maxillary incisor display: distance from stomion superius to the maxillary incisor edge (incisor show). If the two central incisors are not in the same level, two measurements were taken and the average was used (figure 1).

Fig (1) Measurements of smile taken from photographs: 1= Lip length, 2= Lip thickness, 3= Interlabial gap, and 4= Incisor show

All data from photographs were collected tabulated and statistically analyzed using paired “t” test to evaluate changes in the smile components using Micostat7 for Windows statistical package (Microstat Co).

Methods

After careful examination, diagnosis and treatment planning; decision of extraction was mainly governed by the amount of crowding present. Extracted teeth were the first upper and lower premolars or first upper premolars only.

Zero base brackets of slot size 0.020 were placed in the upper and lower arches. Banding of

the upper first permanent molars with triple tube bands and double tube bands in the lower first permanent molars was performed. For anchorage, the transpalatal bar on the upper arch and the lingual arch on the lower arch were inserted.

Intrusion mechanics were applied as described by Burstone. Buccal stabilizing arches of size 0.018 X 0.025 inch stainless steel wires were placed at both sides posteriorly in the upper and lower arches in addition to anterior segment placed on the four incisors. An intrusive arch made of stainless steel wire of size 0.017 X 0.025 inch with 3 mm helix was placed mesial to the auxillary tube. When the arch was tied to the level of the incisors; an intrusive force was developed. It was tied by a ligature wire of size 0.01 inch to the stabilizing segment anteriorly. The intrusive arch was cinched back to avoid flaring of the anterior teeth.

The tension gauge instrument should be used to measure the amount of intrusive force located in the intrusive arch. A force of 100 gm was applied to the upper four incisors and a force of 75 gram was applied to the lower incisors (Foda, 1998).

Patients are recalled periodically every three weeks to confirm maintenance of oral hygiene measures and to assure the condition of the appliance and to reactivate the intrusive arch.

RESULTS

The following results were obtained from lateral cephalometric radiographs and photographs.

1) Lateral cephalometric radiographs

A- Incisor changes

Incisors were intruded and tipped labially. Because of this tipping, their position in relation to the Nasion vertical line was decreased or in other wards the incisors are more approached to the NV line. The length of the incisors measured from the tip of the tooth to the apex of the root was not changed for both the maxillary and the mandibular incisors, which means no root resorption occurred (figure 2).

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B- First molar changes

Molars were not extruded because of using the buccal stabilizing segments (0.018 x 0.025 st st wire) and the use of transpalatal arch on the upper teeth and the lingual arch on the lower teeth.

Molars were slightly tipped buccaly similar to the incisors, their length was not changed that means no root resorption occurred (figure 3).

Fig. (3) Molar changes in lateral cephalometric radiograph

C- Changes in jaw relation:

The atroposterior position of the maxilla (SNA) showed significant increase, this may be due to slight flaring of the upper incisors or may be related to presence of residual growth. While the antroposterior position of the mandible (SNB) recorded a statistically significant decrease because of the backward movement of point B.

The difference between the antroposterior position of the maxilla and the mandible (ANB) showed a statistically significant increase as a result of change in SNA and SNB angles.

Slight autorotation of the mandibular plane angle (SN/MP) was recorded and this resulted from backward movement of gonion, in addition to downward movement of gnathion secondary to autorotation of the mandible after bite opening (figure 4).

Fig. (4) Jaw relation changes in lateral cephalometric radiograph

D- Soft tissue changes

There were statistically significant changes in all parameters. Lip length and lip thickness were increased, while the interlabial gap was decreased (figure 5).

Fig. (2) Incisor changes in lateral cephalometric radiographs

Fig (5) Soft tissue changes in lateral cephalometric radiograph

THE EFFECT OF BURSTONE’S INTRUSIVE MECHANICS (2361)

2) Photographs (digital images)

A significant increase in the lip length and lip thickness was observed, while there was a statistically significant decrease in interlabial gap and maxillary incisor display (incisor show).

These findings resulted in decrease in the amount of gum tissue appearing so leading to more attractive smile (figure 6).

DISCUSSION

The smile is the most recognizable signal in the world. Smiles are such an important part of communication that we see them far more clearly than any other expression. Just as a nice smile can act as a powerful communication tool and unpleasant one can have an equally powerful negative impact (as gummy smile). That is why patients seek orthodontic treatment (Durgekar and Naik, 2010).

So this study was intended and planned to examine the effects of segmented arch mechano-therapy (segmented Burstone intrusive arch) on the correction of anterior deep bite and its effect on the patient’s smile. Bite opening procedures were usually instituted early in the treatment, both to maximize

patient’s cooperation and to allow antroposterior tooth movements that might otherwise be hindered by the deep bite (Foda, 1998).

The study was carried out on female subjects with an age range of 18-25, to assure the presence of least amount of growth. In addition, females have high attendance percentage at the orthodontics department clinic seeking orthodontic treatment. The majority of cases were treated with extraction of either upper or lower first bicuspids or upper bicuspid only. A limited number of patients were treated without extraction. It was found that extraction of teeth had a statistically significant effect in bite opening.

By segmented Burstone technique, it was possible to develop a precise and predictable force system between the anterior and posterior segments enabling pure intrusion of the anterior teeth. Intrusion of the four anterior teeth was accomplished first, followed by canine intrusion. Avoidance of the en-masse intrusion of the six anterior teeth as one unit was implemented to prevent the eruption and the rotation of the buccal segments. This was in accordance with the data from the literature as in Dermaut and Vander-Buleke (1986).

Fig. (6) Pre-operative and post-oper-ative extraoral photographs showing reduced gummy smile

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During intrusion of anterior teeth, optimal magnitudes of forces were used to minimize root resorption and decrease side effects on reactive units. It has been documented that the use of heavier forces did not increase the rate of intrusion.

The amount of intrusive forces applied were 25 gm and 15 gm per tooth for the upper and lower incisors respectively, and this was adjusted by tension gauge as recommended by Burstone (1977) and Costopoulos and Nanda (1996) who applied an intrusive force of only 15 gm for the upper incisors to avoid root resorption. After two months of successful intrusion, the patients’ smile was examined and its components were measured as previously discussed in the materials and methods, by comparing the preoperative and postoperative photographs and lateral cephalometric radiographs.

In this research the results depended mainly on the records taken from lateral cephalometric radiographs and photographs. A little attention was given to the study casts, intraoral periapical radiographs and panoramic radiographs.

1) Lateral cephalometric radiographs

A- Incisor changes

There was a significant intrusion of the upper and lower incisors, and this finding was confirmed by Burstone (1977 & 2001), Molnar et al. (1995), Dermant and Vander-Bulcke (1986) and Diedrich (1990).

Park (1989) experienced the efficiency and superiority of the segmented arch. Julia et al. (2005) concluded that incisor intrusion was achievable in both arches, but true intrusion as the sole treatment option was questionable in non-growing patients. Amit et al. (2011) agreed with the treatment of deep bite with intrusion.

Labial tipping of the upper and lower incisors was observed in spite of cinching back of the arch.

This finding, although rare, was confirmed by Steenbergen et al. (2005 and 2006).

Positions of the incisors were changed as they were tipped labially , in contrary to these findings Bhavna et al. (1995) found that the segmented arch was useful in controlling tooth movement antroposteriorly and vertically.

There was no change in lengths of the incisors observed radiographically (which means no root resorption occurred). This was confirmed by Graber and Swain (1985). Dermaut and Munck (1986) found no correlation between the amount of root resorption and duration of intrusion. Also, the study of Goerigk et al. (1992) and Weiland et al. (1996) minimized the apical root resorption by using calculable force system. Costopoulos and Nanda (1996) revealed that intrusion with low forces caused only negligible amount of apical root resorption. On the other hand Melsen et al. (1989) observed root resorption in maxillary incisors when deep overbite corrected about 3.5 mm.

B- Molar changes

From the results of this clinical research, we can see that no extrusion of the posterior teeth occurred when anterior deep bite was corrected by the segmented Burstone arch, this was confirmed by Weiland et al. (1992). On the contrary, Marcotte (1990) corrected the deep bite with intrusion of the anterior teeth, extrusion of the posterior teeth or combination.

Meyer et al. (1991) results did not agree with our results as he registered extrusion of the posterior teeth and he suggested applying the intrusive force between the centers of resistance of the central and lateral incisors, he also reduced the intrusive force below 0.20 Newton per side to avoid extrusion of the posterior teeth.

Burstone (2001) suggested treatment of deep overbite by extrusion of the posterior teeth in

THE EFFECT OF BURSTONE’S INTRUSIVE MECHANICS (2363)

patients who were still actively growing with short vertical facial dimension.

Beatriz (2011) corrected deep bite by posterior teeth extrusion, anterior teeth intrusion and/or incisor labialization.

Buccal tipping of the posterior teeth was observed in spite of the use of buccal stabilizing segments (0.018 x 0.025 st st wire) and trans-palatal arch. No change in the molar length was observed which means that no root resorption occurred.

C- Changes in jaw relations

Slight autorotation of the mandibular plane angle SN/MP was recorded, which was related to the backward rotation of the gonion and the downward movement of the gnathion secondary to autorotation of the mandible after bite opening.

There was a significant increase in SNA angle which may be due to slight flaring of the upper incisors or may be related to the presence of residual growth.

The SNB angle was decreased because of the backward movement of point B, secondary to bite opening. The ANB angle was increased as the result of change in SNA and SNB angles.

D- Changes in soft tissue

From our soft tissue results we can see that the lip length, lip thickness were increased, and the interlabial gap was decreased (that means lips became more competent). All these changes will produce more esthetic smile and reduce the gummy smile, as most authors reported that there are several etiologies for “gummy smile” including lip length, thickness and activity as confirmed by William (1999).

Peck and Peck (1995) assured that gummy smile was not necessarily objectionable esthetically and diminish with age, in other words as the person ages the smile gets narrower vertically and wider transversely as confirmed by Shyam et al. (2009).

Overbite correction especially maxillary incisor intrusion would lead to flattening of the smile arc that consequently reduces the smile attractiveness as confirmed by Lindauer et al. (2005).

2) Photographs (digital image)

Facial (frontal and profile) colored photographs as well as intraoral shots of different views of dental arches in occlusion were taken before and after bite opening. The results obtained from photographs showed significant increase in lip length and lip thickness, while there was a significant decrease in incisor show and interlabial gap.

All of these results improve the smile and the facial attractiveness.

CONCLUSION

1) Burstone’s intrusive mechanics succeeded in achievement of satisfactory overbite correction in class II division 1 and improvement of gummy smile.

2) No significant root resorption in the incisors or even in the posterior teeth was observed, however caution must be exercised in treating patients who may be “high risk” to root shortening.

3) Significant changes in most of the antroposterior skeletal measurements.

4) Slight autorotation of the mandibular plane angle (SN/MP) was recorded as a result of bite opening.

5) Digital images showed significant increase in lip length and lip thickness with a significant decrease in interlabial gap and incisor show.

6) Regular monitoring by radiographic examination is an important issue for the effects of the intrusive force especially on the maxillary incisors which are considered the most susceptible teeth to root resorption.

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