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

To evaluate the dental and skeletal effects of chin cup using two different force magnitudes in the management of Class III malocclusion cases.

Fifty growing patients (26 males and 24 females) with skeletal Class III and mandibular prognathism were selected. The patients were divided into three groups. Patients in group 1 (n = 20) were treated with a chin cup and occlusal bite plane using 600 g of force per side. Patients in group 2 (n = 20) were subjected to the same treatment as in group 1 but using 300 g of force per side. In group 3 (n = 10) no treatment was performed. For all patients, lateral cephalograms were taken before treatment and after 1 year. Cephalograms were traced and analyzed. The collected data were analyzed statistically using one-way analysis of variance and the Tukey test.

In the treatment groups, the SNB angle and ramus height decreased significantly. The ANB angle, Wits appraisal, anterior facial height, mandibular plane angle, and retroclination of the mandibular incisors were significantly increased in comparison to the control group. Utilization of either force showed no significant differences, except that the reduction in the ramus height was significantly greater with the use of higher force.

The use of a chin cup improved the maxillomandibular base relationship in growing patients with Class III malocclusion but with little skeletal effect. The utilization of either force had the same effects, except that the higher force had a more pronounced effect in reduction of ramus height.