The Orthopedic Chin CapProf. Maher fouda

Prepared by Bilal A. Mohammed

Faculty of dentistry-Mansoura

university - Egypt

Background

A number of appliances are available for the treatment of Class III malocclusion. Among them, chin cup holds a premium position as a traditional appliance for the early orthopedic treatment of Class III malocclusion. However, a thorough and in-depth investigation of the literature reveals controversies and contradictions regarding both its appropriate use and its clinical effectiveness.

Clinical results achieved with the chin cup also constitute a matter of debate. Retardation or even sometimes restriction of mandibular growth is supported by some authors (Proffit 2000, Bishara 2001 and Chang HP 2005), while such effects are questioned by others (Mc Namara 2005,Sugauara 2005, Oppenheim 1944, Thilander 1965).

Since no standard protocol has been followed from various clinicians, it is evident that the effectiveness of the chin cup varies according to the exact and individualized way of use and it ranges substantially betweeninvestigators from minimal to great.

Chin cap

• The oldest of the orthopedic approaches to the treatment of Class III malocclusion.

• - much of the research conducted on Asian populations due to the higher incidences of Class III malocclusion in these groups.

- there are a wide variety of chin cup designs available commercially.

- in general these appliances can be divided into two types:- 1- The occipital-pull chin cup is used in instances of mandibular prognathism. 2- the vertical-pull chin cup is used in patients with steep mandibular plane angles and excessive lower anterior facial height.

occipital-pull chin cup - indicated for use in patients with mild to moderate

mandibular prognathism.- Success is greatest in those patients in the deciduous

and mixed dentition who can bring their incisors close to an edge to edge position when in centric relation.

- useful particularly in patients who begin treatment with a short lower anterior facial height, because this type of treatment can lead to an increase in this dimension.

Soft elastic appliance. The direction of force is determined by the position of the head cap

Soft elastic appliance. The direction of force is determined by the position of the head cap

Force Magnitude and Direction- Chin cups are divided into two types: the occipital-pull chin cup that is used for

patients with mandibular protrusion and the vertical-pull chin cup that is used in patients presenting with a steep mandibular plane angle and excessive anterior facial height.

- Most of the reported studies recommended an orthopedic force of 300-500 grams per side. Patients are instructed to wear the appliance for 14 hrs/day.

Proffit recommended a force of approximately 16 ounces (450 gram) per side through the head of the condyle or a somewhat lighter force below the condyle. Once it is accepted that mandibular rotation is the major treatment effect, lighter force oriented to produce greater rotation makes more sense. From this perspective, it is apparent that more Asian than Caucasian children can benefit from chin-cup treatment because of their generally shorter face height and greater prevalence of lower incisor protrusion, not because of a difference in the treatment response .

-Once the anterior crossbite was corrected, the patient was instructed to wear the chin cup at least 10 hours per day until slight Class II canine and molar relationships were established.

Direction of force- If the pull directed below the condyle, the force of the

appliance may lead to a downward and backward rotation of the mandible.

- If no opening of the mandibular plane angle is desired, the force should be directed through the condyle to help restrict mandibular growth.  

Hickam-type headgear. Used as anchorage for a hard chin cup. The direction of pull can be adjusted according to the placement of the elastics.

- If no increase in lower anterior facial height is desired, the vertical-pull chin cup can be used.

The use of a Hickham-type headcap combined with a hard chin cup allows for variable vectors of force to be produced on the lower jaw.The direction of pull can be adjusted according to the placement of the elastics.

A study by Schulz and co-workers that compared the vertical-pull chin cup combined with the bonded acrylic splint expander to the bonded expander used alone in high-angle patients indicated that a modest improvement can be obtained in the mandibular plane angle and in lower anterior facial height with the use of the vertical-pull chin cup.

- One of the easiest of the vertically directed chin cups to manipulate clinically is shown in the figure below.

- A spring mechanism is activated by pulling the tab inferiorly and attaching the tab to a hook on the hard chin cup.

The vertical-pull chin cup. A, Unitek design. A spring force design is used to create a vertical direction of pull.

- Another type of chin cup - produces a vertical direction of force. - incorporates a cloth headcap that curves around the crown of

the head. - secured posteriorly with two horizontal straps. - This particular design is useful in those patients in whom

anchorage in the cranial region is difficult to achieve.

B, Summit Orthodontics design. A cloth head cap curves around the crown of the head and is secured posteriorly with two horizontal straps. The force is produced by the stretch of the elastic material. In both of these examples, a hard chin cup is shown.

Best patient for Chin cup therapy

Ko et al (2004)

1. Mild Skeletal III, ability to achieve edge to edge incisors

2. Short vertical facial height (.Chincup cause clockwise rotation of the mandible.

3. Proclined or upright LLS (Chincup cause lingual tipping of the lower incisors

(Thilander 1963)

4. Absence of severe facial and dental asymmetry.

5- The earlier the problem is addressed, the more successful treatment appears to be. 6- Multiple “stages” of active chin cup home wear are often required in order to be successful in the case of moderate prognathism. 7- The “corrected” patients need to be monitored at 4- to 6-month intervals until major growth has ceased.

8 -The best age is before canine and premolar erupt (CS2-CS3 maturity) this is the first growth spurt of mandible, the second one when 7 and 8 erupt CS4-CS6 (Bacceti, 2005).

-Patients with mandibular excess can usually be recognized in the primarydentition despite the fact that the mandible appears retrognathic in the early years

for most children . -There is evidence that treatment to reduce mandibular protrusion is more

successful when it is started in the primary or early mixed dentition. The treatment time varies from one year to as long as 4 years depending on the severity of the original malocclusion.

(Thilander 1963) and Peter W. Ngan 2014 Retardation of mandibular growth. Effective at reducing mandibular prognathism

before puberty but this is then lost with continual growth, Sugawara et al., 1990

Remodelling of the condyle and glenoid fossa

Backward rotation of the mandible

Closure of the gonial angle

Result in lingual tipping of LIS,

The effects of chincup therapy

whether the growth of the mandible can be retarded through wearing a chin cup? - Sakamoto and co-workers and Wendell and co-workers have noted decreases in mandibular growth during treatment. - Wendell and associates noted that the mandibular length increases in the treated group were only about two-thirds of those observed in the control group of mixed dentition individuals.

-Mitani and Fukazawa, however, noted no differences in mandibular length in Class III individuals who began treatment during the adolescent growth period in comparison with control values .

- Graber reported that, in a sample of young Class III patients, the predominantly horizontal mandibular growth pattern was redirected more vertically, indicating that the orthopedic chin cup can produce an increase in lower anterior facial height while correcting the anteroposterior malrelationship.- The idea of this appliance is that because the condyle is a growth site, the growth impeded by extra-oral force (Graber, 1977).

- Sugawara and Mitani noted that such treatment seldom alters the

inherited prognathic characteristics of skeletal Class III profiles over the

long term.

- Despite success in animal experiments, most human studies have found

little difference in mandibular dimensions between treated and untreated

subjects (Sugawara et al, 1990). -Chincup appliances greatly improve the skeletal profile in the short

term, such changes are however rarely maintained during the pubertal growth spurt.

In theory, extraoral force directed against the mandibular condyle would restrain growth at that location, but there is little or no evidence that this occurs in humans. What chin-cup therapy does accomplish is a change in the direction of mandibular growth, rotating the chin down and back, which makes it less prominent but increases anterior face height. The data seem to indicate a transitory restraint of growth that is likely to be overwhelmed by subsequent growth.

Contemporary Orthodontics, 5th Edition proffit

In essence, the treatment becomes a trade-off between decreasing the anteroposterior prominence of the chin and increasing face height. In addition, lingual tipping of the lower incisors occurs as a result of the pressure of the appliance on the lower lip and dentition, which often is undesirable.

Contemporary Orthodontics, 5th Edition proffit

Unfortunately, the majority of Caucasian children with excessive mandibular growth have normal or excessive face height, so that only small amounts of mandibular rotation are possible without producing a long-face deformity. Many of these children ultimately need surgery, and the chin-cup treatment is essentially transient camouflage. For that reason, it has limited application.

A typical response to chin-cup treatment. A, Pretreatment profile .B, Posttreatment profile. This treatment reduces mandibular protrusionprimarily by increasing anterior face height, very similar to the effect of Class IIIfunctional appliances.

For chin-cup treatment, a hard plastic cup fitted to a cast of the patient's chin or a soft cup made from an athletic helmet chinstrap can be used. The more the chin cup or strap migrates up toward the lower lip during appliance wear, the more lingual movement of the lower incisors will be produced, so soft cups produce more incisor uprighting than hard ones. The headcap that includes the spring mechanism can be the same one used for high-pull headgear.

Effects on Maxillary Growth Peter W. Ngan 2014

- Some studies have indicated that a chin cup appliance has no effect on the anteroposterior growth of the maxilla.

- Uner et al. showed that early correction of anterior crossbite with chin cup

appliance prevents retarded anteroposterior maxillary growth.

- Sugawara et al. compared the growth changes of patients after chin cup treatment with control subjects and reported that at age17, the midface is more deficient in patients of the control groups than in those of the treatment groups.

Orthodontic Treatment of Class III Malocclusion Editors Peter W. Ngan & Eugene W. Roberts 2014 Bentham Science Publishers Ltd.

Stability of Treatment- The stability of chin cup treatment remains unclear. - Several investigators reported stability in horizontal maxillary and mandibular

changes associated with chin cup treatment. - few studies reported a tendency to return to the original growth pattern after the

chin cup is discontinued. - Sugarwara and colleagues published a report on the long-term effects of chin cup

therapy on three groups of Japanese girls who started chin cup treatment at 7, 9, and 11 years. All 63 patients were followed with serial lateral headfilms taken at the ages of 7, 9, 11, 14, and 17 years.

- the skeletal profile was greatly improved during the initial stages of chin cup therapy, but these changes were not usually maintained.

Reverse chin cup therapy• Developed in Germany in 2012 by Rahman 2012 show similar result when the reverse chin cup therapy compared to face mask therapy involving 42 samples at age of 8-9 years.• Reverse chin cup therapy is able to produce forward movement of the maxilla in the growing child associated with lingual tipping of the lower incisors and labial tipping of the uppers.

• The point of application of protraction elastics from the upper removable appliances was similar for both groups. All patients received the same protraction force of 500 g per side with a 30 degree downwards pull.• The proposed advantages of the new reverse chin cup design were that it was smaller and less bulky than other protraction appliances, therefore encouraging children to wear it.

Evidance base

Systematic review and meta analysis

for growing patients presenting Class III malocclusion and/or open bite, could chin cup, as compared with no treatment at all, be beneficial for the improvement of their facial, skeletal and dentoalveolar characteristics in the

short and long term?????

Although the initial plan was to investigate the short and long-term effects of both the occipital and the vertical pull chin cup, due to the limited data provided from the included articles, only the short-term occipital pull chincup effects were finally examined. Consequently, where the term ‘chin cup’ is used thereafter, it is referred to the occipital pull chin cup, and where the term ‘clinical effects’ is used, it is limited to the short-term ones.

Soft tissue, model cast and perioral muscular electromyography data analyses were also not possible to be performed because no such data could be retrieved as appropriate for inclusion and analysis in the presentstudy. Thus, treatment effect comparisons between the experimental groups were considered just for skeletal and dentoalveolar alterations as measured on lateral cephalometric radiographs.

Effectiveness of chin cup treatmentThe common cephalometric variables retrieved from the seven included treated groups and possible to be examined in current MA were the following: (a) skeletal variables in the sagittal plane: SNA (°), SNB (°), ANB (°), Wits appraisal (mm) and Co-Gn (mm); (b) skeletal variables in the vertical plane: SN-ML (°), gonial angle (°), N-Me (mm), UFH (mm), LAFH (mm) and Co-Go (mm) and (c) dentoalveolar variables: overjet (mm) and overbite (mm).

The contribution of the original studies to the investigation of eachindividual cephalometric variable is presented in this Table.

Meta-analyses were performed for the variables SNA, SNB, ANB, Wits appraisal, SN-ML and gonial angle, where data from five or more treated groups derived from the included studies contributed in the analysis. For therest of the variables, namely Co-Gn, N-Me, UFH, LAFH, Co-Go, overjet and overbite, where data from four or less treated groups contributed in the analysis, exploratory analyses were performed.

With regard to the skeletal cephalometric changes in the sagittal plane, it was revealed that there was statistically significant reduction in the SNB angle of the patients treated with the chin cup in comparison to the untreated individuals (SDM = −1.97, CI = −3.09 to −0.84, P = 0.001),indicating a restriction effect on mandibular growth .

In addition, Class III malocclusion of treated patients was significantly improved since there was a statistically significant increase following chin cup use in comparison to untreated individuals to (a) the ANB angle (SDM = 2.48, CI = 1.36 to 3.61, P = 0.000) and (b) the Wits appraisal (SDM = 3.62, CI = 1.32 to 5.92, P = 0.002).However, for all these three variables, the observed data heterogeneity as well as the between-studies variance was high.

With regard to the skeletal cephalometric changes in the vertical plane, the results of the MA revealed that the SN-ML angle increased significantly whereas the gonial angle decreased significantly in the patients treated with the chin cup as compared with the untreated individuals (SDM = 1.17, CI = 0.48 to 1.86, P = 0.001 and SDM = −0.80, CI = −1.52 to −0.08, P = 0.030, respectively), indicating a tendency towards an increase of the vertical growth pattern and/ or posterior rotation of the mandible .

However, data heterogeneity of the included studies was moderate tohigh, and the between-studies variance was moderate.The tendency towards increase of the anterior face height is further supported by the statistically significant increase of the linear variable N-Me according to the exploratory analysis performed (SDM = 1.39, CI = 0.59 to 2.18, P = 0.001). Moderate data heterogeneity of the included studies and small between studies variance were also observed here.

As far as the dentoalveolar changes are concerned, the results of the exploratory analysis revealed that there was a statistically significant increase of overjet in the patients treated with the chin cup in comparison to the untreated individuals (SDM = 2.62, CI = 1.06 to 4.19, P = 0.001), indicating an improvement of the antero-posterior relations of the maxillary and mandibular incisors. Yet, data heterogeneity observed in the included studies, as well as the between studies variance, was high.

For the rest of the variables, namely SNA, Co-Gn, UFH, LAFH, Co-Go and overbite, no statistically significant differences were derived .

Finally, due to the limited data provided from the included articles, no long-term effects following the use of the occipital chin cup, as well as no short- and long-term effects of the vertical pull chin cup, could be investigated.

ConclusionsAlthough the aim of this investigation was to assess the short- and long-term effects of both the occipital and the vertical pull chin cup, due to the lack of appropriate data of the included articles, only the short-term occipital pull chin cup effects were possible to be assessed. In addition, soft tissue, model cast and perioral muscular electromyography data analyses were also not possible to be performed for the same reasons.

Thus, according to the results of this investigation, it can be concluded that following the use of occipital pull chin cup for the short-term management of growing patients with Class III malocclusion before pubertal spurt, an overall significant improvement of the skeletal and dentoalveolar relationships takes place in comparison to untreated individuals. In detail, data elaboration leaded to the following conclusions: - The skeletal Class III sagittal relationships of the maxilla and mandible are improved.

-The skeletal Class III vertical relationships are also affected towards an increase of the vertical growth pattern, an increase of the anterior face height, and/ or posterior rotation of the mandible.

- The antero-posterior relations of the maxillary and mandibular incisors, as indicated by the increase of overjet, are improved.

Nevertheless, the limited number of included studies, the high heterogeneity observed in most of the variables and the linear manner of many of them suggest some precaution in the interpretation of these conclusions. It seems that there is not enough evidence-based data to make definitiverecommendations about the chin cup treatment.More high-quality evidence-based clinical trials with proper design, sample size, appliance use and measurements nare needed in the future in order to reach more reliable results concerning the chin cup treatment of Class III malocclusion in the short and the long term.

Studies and case reports

A comparison of chincap and maxillary protractionappliances in the treatment of skeletal Class III malocclusions

Material and methods Lateral ccphalomctric radiographs o f 168 previously treated skeletal Class III malocclusion patients wrre traced an d digitized. They were evaluated with the JOE program (Rocky Mountain Orthodontics JO E Version S.O'Denver. USA ). This program makes considerations about the malocclusion type and its origin by analysis of several ccphalomctric parameters. Sagittal considerations made by this program are based on facial depth (NPg/frankfort horizontal), maxillarydepth (NA/Frankfort horizontal) and corpus length (Xi-Pg). After the evaluation o f the 168 cases, the considerations in the program showed that only 24 cases had a skeletal Class III malocclusion with a combination of maxillary retrusion and mandibular protrusion. Others were either maxillary retrusion or mandibularprotrusion cases.

When the treatment types of the 24 skeletal Class III cases with a combination o f maxillary retrusion and mandibular protrusion were investigated.it was found that 12 subjects were treated with chincap appliances and 12 with a maxillary protraction appliance.The first group o f 12 patients (six girls and six boys) with a mean age o f 11.03 years were treated with a chincap an d mandibular occlusal bite plate.

'Ihe chincap applied a total force of 600g. The patients were instructed to wear the appliance for at least 14-16 hours a day.The second group comprised 12 children (seven girts and five boys) with a mean age 10.72 years Maxillary protraction therapy was applied in this group. They were

treated by using Dclairc type orthopaedic faccnusk and a removableintra-oral appliance with an anterior point application.

The total force applied was 600 g and the patients were instructed to wear the appliance for approximately 16 hours a day. When a normal dental relationship was obtained with a 2-3 mm overjet. lateral ccphalometric radiographs were taken in both groups The treatment time was 10.0 months for the chincap group and 11.7 months foe the maxillary protraction group.

ResultsThe statistical comparison of the pre – treatment values be tween the groups sho we dsignificant differences in upper incisor/N A relations ( degree -mm )

C hine cap groupSNB and facial axis showe dsignificant d ecreases in the chin cap group . There was astatistically significant increase in this group in Co –A, ramus height , ANB , lower face height and anterior and posterior face heights . Evaluation of dental relationships during chincap therapy showed Significant increases in upper incisor -NA (mm ) and over jet Angular and dimensional parameters For lower incisor -NB and molar relationship showed a significant decrease in this group. Soft tissue analysis demonstrated a significant increase in upper lip length an d a significant decrease in nasolabial length.

Face mask groupS-N length. SNA. C o -A. SMGoGn. Ramus height. Co-Gn. ANB. lower face height, and anterior and posterior face heights showed a significant increase at the en d o f the orthopaedic face mask therapy. Significant decreases were observed in SNB. facial depth, facial axis, and maxllo-mandibular differential. The inter-incisalangle significantly decreased. There was a significant increase in overjet. and significant decreases in overbite and molar relationship in the maxillary protraction group. Evaluation of the soft tissues demonstrated a significant increase in upper lip length.

Comparison o f chincap and face mask therapy The SNA angle increased significantly more in the maxillary protraction group compared with the chincap group. Angular and dimensionalparameters for lower incisor-NB showed significant differences between the groups. There was a significantly greater increase in the molar relationship in the maxillary protraction group than in the chincap group. While the nasolabial angle significantly decreased in the chincap group, there was a non-significant increase in the maxillary protraction group and the difference between the groups was statistically significant.

Chin cup treatment for class III maloclussions: little evidence to assess impact on temporomandibular

joint

Posted byDerek Richards

MethodsSearches were conducted in Medline/PubMed, Embase, the Cochrane Oral Health Group’s Trials Register, CENTRAL, ClinicalTrials.gov, the National Research Register, and Pro-Quest Dissertation Abstracts and Thesis database. Prospective and retrospective studies, including randomized clinical trials(RCTs), controlled clinical trials, and other observational studies were considered in this review. Studies with or without auxiliaries, such as lingual arches or other intraoral mechanotherapies that had outcomes including morphological adaptations of the TMJ, changes of the condylar configuration, dysfunctions caused by the chin-cup therapy, and incidence and types of TMD were included. Study selection, data abstraction a quality assessment was carried out independently by two reviewers.

Results• 12 studies were included• 8 were prospective, 4 retrospective. There were no RCTs.• One of the prospective studies was considered to be at low risk of bias.• 5 studies considered chin-cup influence on craniofacial structures and condylar shape• 7 studies considered chin-cup influence on TMD• A qualitative summary of the studies was presented. This suggests that:-

o chin-cup therapy affects the condylar growth pattern, even though two studies reported no significance changes in disc position and arthrosis configurationo chin-cup therapy constitutes no risk factor for TMD.

ConclusionsThe authors concludedBased on the available evidence, chin-cup therapy for Class III orthodontic anomaly seems to induce craniofacial adaptations. Nevertheless, there are insufficient or low-quality data in the orthodontic literature to allow the formulation of clear statements regarding the influence of chin-cup treatment on the temporomandibular joint.

Chin Cup Therapy: An Effective Tool for the Correction of Class III Malocclusion in Mixed and

Late Deciduous DentitionsThe Journal of Indian Orthodontic Society,

October-December 2010;44(4):109-114

In Class III malocclusion, it is the treatment objective to restrain all possible horizontal mandibular growth, or at least redirect it into a more vertical vector as the maxilla continues to grow downward and forward. Since Class III faces tend to become more prognathic, and cause unfavorable muscle and tooth adjustments, it is good interceptive dentofacial orthopedics to place appliances early where there is Class III malocclusion.

Therapy should eliminate the malrelationship in any event. Many pseudo Class III cases have a tendency to become full blown Class III later on during the growth period unless treated.

The ideal patient for chin cup or functional appliance treatment of excessive mandibular growth has:

1 .A mild skeletal problem with the ability to bring the incisors end-to-end or nearly so

2 .Short vertical face height3 .Normally positioned or protrusive, but not retrusive lower incisors.

What chin cup therapy does accomplish is lingual tipping of the lower incisors as a result of the pressure of the appliance on the lower lip and dentition and a change in the direction of mandibular growth, rotating the chin down and back. Children who have increased lower anterior face height and are treated with chin cups may end up with skeletal open bites after treatment. Chin cups are divided into two types:

1 .The occipital-pull chin cup, more frequently used in cases of mandibular prognathism and,

2 .Vertical-pull chin cup that is used in cases of steep mandibular plane angle and excessive anterior facial height, the so-called “backward rotator” patient with openbite.

The time duration of chin cup wear depends on the age when the appliance is placed and the magnitude of the malocclusion as well as the amount and direction of growth at the time.

After the correction of a pre-existing anterior crossbite has been accomplished, the patient wears the appliance during the night only as a retention appliance.

CASE REPORTSCase 1

A female patient aged 7 years reported to the Department of Orthodontics and Dentofacial Orthopedics with a chief complaint of forwardly placed lower front teeth.

On examination, she was brachyfacial, had a concave profile, an everted lower lip with a deep mentolabial sulcus.

Intraorally, she had a mesial step terminal plane on right and left side. The overjet was 1 mm and overbite was also 1 mm with a posterior crossbite on right side.

Cephalometric analysis showed a Class III skeletal tendency, a horizontal growth pattern, a decreased lower anterior facial height and proclined upper and lower incisors.

The patient was treated with a chin cup therapy with a slow maxillary expansion (SME) screw to correct right side posterior crossbite along with Z spring to procline the left central incisor for the correction of anterior crossbite.

After 11 months of treatment, forward growth of maxilla was observed with restricted growth of mandible and a normal interarch relationship with increased lower anterior facial height obtained. We have a follow-up of almost 2 years post-treatment.

Post-treatment extraoral (case 1)

Presently, the patient is wearing chin cup only at night time for retention. Fixed mechnotherapy will be initiated after eruption of all permanent teeth, if required.

Case 2A male patient aged 10 years reported to the Department of Orthodontics and Dentofacial Orthopedics with a chief complaint of forwardly placed lower front teeth.

On examination, he was found mesofacial, had a concave profile, an everted lower lip with a deep mentolabial sulcus.

Intraorally, he had a mesial step terminal plane on right and left side. The overjet was 1 mm and overbite was 2 mm with mildly crowded lower anterior teeth

Cephalometric analysis showed a Class III skeletal tendency, a horizontal growth pattern, a decreased lower anterior facial height and proclinated upper and lower incisors. The patient was treated with a chin cup therapy.

After 13 months of treatment, forward growth of maxilla was observed with restricted growth of mandible and a normal interarch relationship with increased lower anterior facial height obtained.

for retention the patient worn the chin cup only at night time. Fixed mechnotherapy will be initiated after eruption of all permanent teeth.

The question concerning the ability to alter the mandibular growth pattern with a chin cup should be regarded in the light of all the variables that may influence growth. Previous studies on the effects of the chin cup force on growing human mandibles have reported various results. There have been a number of clinical studies that have evaluated the treatment effects produced by chin cup therapy.1-4

These studies have shown treatment effects that are somewhat distinct from those discussed earlier regarding the orthopedic facial mask and the FR-3 of Frankel.

One of the substantive concerns, particularly in the treatment of the patient with mandibular prognathism, is whether the growth of the mandible can be retarded during treatment.

Wendell2 et al (1985) have noted decrease in mandibular growth during treatment. Wendell2 et al when examining a group of Class III patients treated in the mixed dentition noted that mandibular length increased for the treated group were only 60to 68% of the control group. Mitani and Fukazawa3 (1976) noted no differences in mandibular length in Class III patients who began treatment during the adolescent growth period. These findings support the observations of Sakamoto1 (1981) andSugawara4 et al (1990) who advocate the use of the occipitalpull chin cup as early as is practical. Whether the ultimate length of the mandible can be influenced by chin cup therapy still remains unclear.

The Effects of Chin Cup Therapy on the Mandible: A Longitudinal Study

Peter D. WendellUniversity of Connecticut School of Dental Medicine,

Farmington, Conn , 1983

Am. j. Orthod.Februry 1984

This study was conducted to evaluate the effects of chin cup therapy on the mandible and its dentition in skeletal Class III patients. The patients selected for this study were Japanese females treated only with the extraoral chin cup appliance. Both the control and treatment samples were obtained from Japanese universities, where these longitudinal data were gathered. Lateral cephalometric radiographs were taken on the average every 6 months for the treatment group and every year for the control group.

Ten treated patients and seven control subjects were studied. The durationof chin cup therapy was variable but averaged 3 years 1 month. The cephalograms were digitized on an electronic screen, and a cephalometric analysis was recorded from a computer program. A Cartesian coordinatesystem was used to enable measurement relative to given x and y reference lines. Subsequent cephalograms for a patient were superimposed, using detailed cranial base structures. The cephalometric measurements were plotted against the patient’s chronologic age in order to obtain a rate-of-change value from a regression line.

The rate-of-change values were then compared with the control group to yield comparison of changes in mandibular growth rate, direction, and pattern in the treatment group. Active and posttreatment effects were evaluated: (1) All measurements for the rate of change of absolute mandibular length (ramal length, body length, and total mandibular length) were reduced by 60% to 68% from the control rate of growth during therapy. These parameters continued to show a decrease of 55% to 61% following active treatment. (2) The mandible exhibited less downward displacement.relative to cranial base, during treatment.

(3 )The mandibular plane angle and the gonial angle closed with growth in the Class III control sample but were variable in the treatment group. (4) The skeletal profile was improved with treatment. (5) Dental changes indicated that an orthopedic correction occurred so that the dentition exhibited a more normal migratory displacement into a favorable Class I occlusion. This study indicates that the chin cup may be a viable mode of treatment for preadolescent and adolescent mandibular prognathism patients.

Chin Cap Force to a Growing MandibleLone-term clinical reports

The cases reported in this study were three Japanese females who had undergone several years o f chin cap treatment.The sample includes different types of prognathic skeletal patterns in terms of the relative size or position o f maxilla and mandible.A chin cap was applied to the mandible with a force o f 500-600gm at the chin during the treatment period. The applied force was directed toward the condylar head o f the mandible

within a small range of variation. The design o f the chin cap is shown in Fig. 1.

The type of chin cap appliance used by the patients in this study. The cup was pulled up by on rubber elastic on each side, with ends attached on different straps. Average force level at the chin rangedfrom 500-600gm.

Measurements used in this study. The long axis of the condyle is drawn through the midpoints of the widest and narrowest parts o f the head and neck.The condyle point, Cd, is located by the intersection of the longaxis with the condyle surface. Linear measurements are made between the established points. The gonial angle is centered on Go and measured to the tangent lines.

The investigation is based on serial lateral cephalometric radiographs taken at three-month intervals, along with semiannual records o f standing height and wristhand radiographs. Each subject maintained time tables in which every hour of chin cap use was recorded.Two o f these cases were treated with a chin cap as an adjunct to an intraoral appliance for several years, and one was treated solely with a chin cap. Since two cases were treated orthodontically along with a chin cap, the changes in the face may include treatment effects other than those produced by the chin cap therapy. However, the study was based on the area where orthodontic therapy is thought to be least effective.

The cephalometric points, planes and diagram for angular and linear measurements employed in this study are shown below. These include overall mandibular length (Cd-Pog), mandibular body length (Go-Pog), mandibular ramus length (Cd-Go), and the gonial angle. Measurements were made every six months. The individual growth data for each point was then combined on a graph to describe the semiannual incremental changes.

Case reporta female, with X first records taken at eight years and four months o f age. The lateral cephalometric diagram shows an evident depression o f the middle face as well as a remarkable protrusion o f the chin when compared with the normal pattern for this age. It also indicated a procumbent mandibular plane and some upward and forward rotation o f the mandible. Mandibular movements to all functional positions were felt to be smooth and normal, but a forward positioning of the mandible was noted during occlusion.From the rest to occlusal position, the central incisors showed a premature contact. The mandible then shifted forward to gain buccal occlusion. Airway was clear and showed no pathological breathingproblem.

Case 1 (age 8yr 4mo), cephalometric diagram. Broken line outlinesaverage female face at age 7yr 7mo ± 18mo. Superimposition is onNasion, oriented on Frankfort horizontal. Black indicates patientoutside the average outline, shading indicates patient inside theaverage outline.

Dental occlusion shows crossbite o f the incisors, deep overbite and noticeable underjet. This patient was treated with a chin cap and intraoral appliance. The figure below shows the occlusion on the final record taken at the age o f 17 years and 4 months. The cephalometric diagram shows the size and position o f the mandible to be fairly well balanced, yet the middle face is still retarded in relation to the normal pattern.

Superimposition o f the radiographs on the anterior cranial base structures during wear o f a chin cap shows a dramatic change in mandibular position.This change occurred through correction of the functional forward positioning o f the mandible. After the change o f the position, forward growth o f the chin was more inhibited, and the chin was displaced downward. Superimposition after discontinuation o f the chin cap shows almost no skeletal change. The changes accomplished during chin cap wear seemed to be retained well.

Superimposition o f the mandible on the mandibular plane at menton shows peculiar change during the active chin cap period, with growth at thecondyle as well as the posterior border of the ramus, and a decrease in the gonialangle.

Chin cup effects using two different force magnitudes in the management of Class III

malocclusionsYasser L. Abdelnabya; Essam A. Nassarb

Fifty growing patients were selected for this study (26 boys and 24 girls). They were selected according to the following criteria: skeletal Class III pattern (ANB angle , 1 degree) and protrusive mandible (SNB angle . 80 degrees). All patients had anterior crossbite.Hand-wrist radiographs were obtained for each patient to assess skeletal maturation.All patients had not passed the peak of pubertal growth spurt, as shown by the epiphysis of the middle phalanx of the third finger having capped its diaphysis. The patients were randomly divided into three groups. Group 1 consisted of 20 patients (10 boys and 10 girls), group 2 consisted of 20 patients (11 girls and 9 boys), and group 3 consisted of 10 patients (5 boys and 5 girls).The mean ages at the start of treatment were 9.6, 10.1, and 9.2 years for groups 1, 2, and 3, respectively.

Patients in groups 1 and 2 were treated with an occipital pull chin cup (Dentaurum, Ispringen, Germany) and an acrylic occlusal bite plane with athickness that just freed the occlusion anteriorly. The chin cup used was soft not acrylic. The force magnitude exerted by the chin cup was 600 g perside in group 1 and 300 g per side in group 2. A force gauge (Somfy tec, France) was utilized to determine the applied force. The patients were instructed to wear the appliances for 14 hours each day. In group 3, thepatients did not receive any orthodontic or orthopedic treatment during the study period.

Lateral cephalogram films were taken for all patients at two stages: before the start of treatment and after 1 year. All films were traced by one investigator. Measurements obtained were corrected for standard magnification. The cephalometric films were retraced and the method error was determined with Dalhberg’s formula; the error was less than 1 mm and 1 degree.

Clinically the anterior crossbite was corrected in all patients in the two treatment groups (Figures 1and 2).In general, there were significant differencesin the changes in cephalometric measurements between the two treatment groups and the control group regarding mandibular position (SNB angle), the maxillomandibular relationship (ANB angle and Wits appraisal), ramus height (Ar-Go), vertical measurements (N-Me and SN-MP angle), and inclination of the mandibular incisors (1-MP). In the treatment groups, the SNB angle, ramus height, and mandibular incisor inclinations were significantly decreased in comparison to the control group. The ANB angle, Wits appraisal, SN-MP angle, and anterior facial height were significantlyincreased in the two treatment groups.

RESULTS

Figure 1. Pre and posttreatment intraoral photographs of patient utilized chin cup with 600 grams of force per side.

Figure 2. Pre and posttreatment intraoral photographs of patient utilized chin cup with 300 grams of force per side.

Regarding the differences in the changes in cephalometric measurements between the two treatment groups utilizing either force magnitude (600 vs 300 g per side), no significant differences were found except in ramus height (Ar-Go). The reduction in ramus height was more pronounced with the utilization of 600 g of force per side than the use of 300 g of forceper side.

Chin cup therapy for mandibular prognathism

lee W. Graber, D.D.S., M.S., MS.Am. .J. O&hod. July 1977 volume 72 no.1

Thirty patients with skeletal Class III malocclusion under treatmentwith the chin cup appliance, averaging 6 years of age at the start oftreatment, were followed longitudinally for a 3-year period. This treatmentsample was compared cephalometrically with an analogous untreated Class III sample.The following significant craniofacial alterations were noted in the samplethat underwent orthopedic chin cup therapy:

1 .A retardation of vertical ramus growth.2 .A retardation of vertical development in the posterior aspect of the

mandibular body.3 .A retardation

3 .A retardation of vertical development in the posterior maxilla.4 .A closure of the gonial angle.

5 .A distal rotation of the mandibular complex.6 .A decreased amount of anteroposterior anterior cranial base growth.

7 .A redirection of the predominantly horizontal mandibular growthpattern to a more vertical direction.

8 .A reduction of the maxillomandibu1a.r malrelationship towardnormative values.

9 .A production of an Angle Class I dental relationship following theestablishment of normal maxillomandibular relations.

10 .A lack of detectable localized effect on the symphyseal region orincisor position as a direct result of chin cup placement and pressure.

11 .Development of soft-tissue profile changes in harmony with underlyingskeletal changes.While all of the listed

gain increased importance when considered together. With orthopedic chincup therapy, there is a change in craniofacial pattern leading to the observed resolution of the Angle skeletal Class III malocclusion. This study thus provides strong support for the use of the orthopedic-force chin cup appliance in the clinical management of young patients with skeletal mandibular prognathism.

Major contributions to correction of the Class III skeletal malocclusion. 1, The mandiblerotated posteriorly, placing the ramus in a more vertical orientation to the cranialbase; 2, the gonial angle was decreased, re-establishing the mandibular plane by overcoming changes introduced by posterior mandibular rotation; 3, vertical condylar growth was restricted; 4, the maxilla rotated slightly in a “clockwise” direction.

Evidence-Based OrthodonticsEdited by

Greg J. Huang, DMD, MSD, MPHStephen Richmond, BDS, DOrth RCS, MScD,

FDSRCS, PhD, FHEAKatherine W.L. Vig, BDS, MS, DOrth RCS, FDSRCS

A John Wiley & Sons, Inc., PublicationThis edition fi rst published 2011 © 2011 by Blackwell Publishing, Ltd.

A chin cup was initially thought to reduce the growth of a prognathic mandible.Although animal studies indicated the possibility of altering condylar growth (Petrovic, Stutzmann & Oudet 1975 ; Copray, Jansen & Duterloo 1985 ; Vardimon et al. 1994 ), clinical research reveals initial changes within the skeleton that were rarely maintained during pubertal growth (Sugawara & Mitani 1993 ). The separate effect of the chin cup versus maxillary protraction is not known and would be difficult to determine. The chin cup may have an additive influence, maximizing the effect of the protraction, and/or mandibular rotation.