Effects of reciprocal mini-chin cup appliance used in early and late treatment period

-142- SUMMARY The aim of this study was to evaluate the dentofacial effects of reciprocal mini-chin cup appliance on cases having pubertal growth and development potential and on cases that have completed this period. In this research 27 cases with Angle class I or II malocclusion, with mandibular dentoalveolar retrusion and with optimal vertical facial dimension were included. Two application groups were constructed according to their growth and development potential, evaluated by the hand-wrist radiographs. A control group consisting of 14 cases was constructed to eliminate the growth and development effect for the first application group who has pubertal growth and development potential. At the beginning and at the end of the application/ control period, lateral cephalometric, hand-wrist and panoramic radiographs, photographs and orthodontic models were obtained from all of the groups. In the first application group there were 13 cases (mean age 12.28 years), in the second application group, 14 cases (mean age 17.55 years), in the control group, 14 cases (mean age 12.06 years). In both application groups reciprocal mini-chin cup was applied. Class I molar relationship was achieved with an average of 5.11 months in the first application group and 10. 57 months in the second application group. On lateral cephalometric tracings, 24 linear and 23 angular parameters to evaluate the effects of RMCC and 8 parameters to determine the ratio of skeletal and dental effects of reciprocal mini-chin cup were measured and evaluated statistically.-143 In both application groups no effect of RMCC was found on maxilla and the sagital position of mandible. In cases having growth and development potential, lower anterior facial height was increased more compared to young adults; mandibular plane angle increased and mandible developed mostly in the vertical dimension. Class I molar relationship, correction of overbite and overjet were achieved in both application groups, yet more correction of overjet was found in the first application group. In both application groups retrusion of upper incisors without extrusion, protrusion and proclination of lower incisors were determined. Distalization of upper molars, mesialization and extrusion of lower molars and also mesialization of mandibular dentoalveolar structure were observed in both groups. In the first application group, dentoalveolar and skeletal contributions in the correction of overjet were 95.47 %, 4.53 % respectively; in the second application group dentoalveolar contribution was 88.02 % and skeletal contribution was 11.98 %. In the first application group, dentoalveolar and skeletal contributions in the correction of molar relationship were 94.16 %, 5.84 % respectively; in the second application group dentoalveolar contribution was 86.65 % and skeletal contribution was 13.35 %.