Force distribution of the temporomandibular joint and temporal bone surface subjected to the head-chincup force

Management of Developing Skeletal Class III Malocclusion in a Prepubertal Girl with Prognathic Mandible in Late Mixed Dentition

Treatment of skeletal Class III patients at younger age is highly unpredictable. The patient may respond well to the treatment or may show excessive mandibular growth during growth spurt which may require orthognathic surgery later on. If not treated at earlier stages of life, the condition may worsen with time. This case report will present the comprehensive orthodontic management of a 9-year-old prepubertal girl in late mixed dentition with prognathic mandible. Chin cup therapy was started and continued for 3 years. After chin cup therapy, maxillary and mandibular dentition were bonded with standard edgewise appliance. After leveling and alignment, Class III elastics were started. Fixed orthodontic treatment was completed in 3 years. At the end, good Class I molar and canine relationship with normal overjet and overbite were achieved. The total treatment time of orthopedic and orthodontic correction was 6 years, 2 months. The patient revealed the same Class I molar and canine relationship after 6 years of treatment. Redirection of mandibular growth pattern from hyperdivergent to normodivergent advocates the use of chin cup as a viable treatment regimen for the management of prognathic mandible in prepubertal patients.

Clinical effectiveness of chin cup treatment for the management of Class III malocclusion in pre-pubertal patients: a systematic review and meta-analysis

Background

Chin cup is regarded as the oldest orthodontic appliance for the management of Class III malocclusion. To assess its clinical effectiveness in pre-pubertal patients, a meta-analysis on specific cephalometric values is attempted.

Methods

Detailed electronic and hand searches with no restrictions were performed up to July 2014. Only randomized controlled trials (RCTs) and cohort studies, i.e. prospective controlled trials (pCCTs) and (retrospective) observational studies (OS), were included. Analyses were performed by calculating the standard difference in means and the corresponding 95% confidence intervals, using the random effects model. Data heterogeneity and risk of bias assessment of the included studies were also performed. Study selection, data extraction and risk of bias assessment were performed twice. The level of significance was set at P ≤ 0.05 for all tests, except for heterogeneity (P ≤ 0.1).

Results

Seven treated groups from five studies (no RCTs, four pCCTs, one OS) were eligible for inclusion, assessing only the short-term occipital pull chin cup effects. In total, 120 treated patients (mean age: 8.5 to 11 years) compared with 64 untreated individuals (mean age: 7.3 to 9.89 years) were assessed by means of 13 cephalometric variables. The overall quality of these studies was low to medium. In comparison to untreated individuals, the SNB and gonial angles decreased significantly following chin cup use, whereas ANB, Wits appraisal, SN-ML, N-Me and overjet increased. For the rest of the variables, no statistically significant differences were detected.

Conclusions

Although the occipital chin cup affects significantly a number of skeletal and dentoalveolar cephalometric variables, indicating an overall positive effect for the treatment of Class III malocclusion, data heterogeneity and between-studies variance impose precaution in the interpretation of the results.

Electronic supplementary material

The online version of this article (doi:10.1186/s40510-014-0062-9) contains supplementary material, which is available to authorized users.

Craniofacial features of patients with Class III abnormalities: growth-related changes and effects of short-term and long-term chincup therapy

The craniofacial features of patients with Class III abnormalities, including growth-related changes and effects of short-term and long-term chincup therapy, were studied. Twenty female subjects were treated with chincups and an orthopedic force of 500 g for 31 months (short-term treatment group). Another 36 female patients were treated with chincups and a force of 250 to 300 g for 86 months (long-term treatment group). All subjects treated with chincups had lateral cephalograms taken before treatment (T0), after treatment (T1), and at retention (T2). Cross-sectional lateral films of 562 skeletal Class III girls were selected from the records of 1265 Class III patients at a public hospital and private clinics as controls. The controls were selected to approximately match the ANB angle, Wits appraisal, and chronological age of the treated groups. Short-term treatment resulted in a slight improvement in ANB angle and Wits appraisal, while long-term treatment resulted in a significant improvement in ANB angle and Wits appraisal. Such treatment also resulted in a significant inhibition of the growth of the ramus (2.2 mm) and body length (3.6 mm) of the mandible, a backward rotation of the mandible, and a reduction (8.2 degrees ) of the gonial angle. However, there was no alteration of any parameter of the maxilla and the cranial base, except the length of S-N and N-S-Ar in the long-term treatment group. Subjects who completed the long-term treatment protocol retained the changes by wearing the appliance during sleep, with a force of 200 g applied to the center of the chin.

Craniofacial adaptations induced by chincup therapy in Class III patients

The purpose of the present study is to examine the effects of an orthopedic force produced by chincup treatment in patients with Class III malocclusion. Anteroposterior maxillary and mandibular changes were examined as were changes in the vertical dimension. Further, the possibility of posterior displacement of temporomandibular joints in treated Class III subjects was evaluated. Serial lateral headfilms of 22 young females (average age, 9 years), who had received chincup therapy were compared with those of 20 skeletal Class III subjects of similar age who received no treatment during the interval studied. A computerized x-y coordinate program was applied to analyze the cephalometric landmarks and measurements. The treated group showed improvement of the skeletal Class III pattern associated with a slight increase (0.8 degrees per year) in SNA and a slight decrease (-0.7 degrees per year) in SNB and also a decreased gonial angle. The distance from the condyle to the chin (Co-Gn or effective mandibular length) increased significantly less in the treated group in comparison with controls. Increases in lower anterior facial height were not different between the treated and untreated groups. In addition, the cranial base angles N-S-Ba and N-S-Ar showed no statistical difference between groups, but these angles tended to increase with time in both groups. Basion and Articulare showed almost the same amount of backward and downward movement in both groups. The results of this study indicate that the primary effect of chincup therapy was in producing a reduction in mandibular growth increments during the period studied. Maxillary growth was not affected during treatment. Further, the results of this study fail to support the hypothesis that chincup appliance significantly induces the posterior displacement of the glenoid fossa.