Effects of the reciprocal mini-chin cup appliance

The aim of this prospective study was to evaluate the dentofacial effects of the reciprocal mini-chin cup (RMCC) appliance in subjects with pubertal growth and development potential (group 1) and in subjects that had completed this period (group 2). Eighteen patients (13 females, five males) with an Angle Class II division 1 and nine patients (six females, three males) with a Class II division 2 malocclusion, with mandibular dentoalveolar retrusion and optimal vertical facial dimension were included. A control group consisting of 14 subjects (nine females, five males) with pubertal growth and development potential was constructed for comparison with group 1. In both treatment groups a RMCC was used. A Class I molar relationship was achieved in an average period of 5.11 months in group 1 and 10.57 months in group 2. From lateral cephalometric tracings, beside the angular and linear parameters, eight parameters that determined the ratio of the skeletal and dental effects of RMCC were measured and statistically evaluated. A paired comparison t-test was used to assess the differences in each group and a Student's t text to evaluate the differences between the groups. In both groups, no effect of RMCC was found on either the maxilla and/or the sagittal position of the mandible. In group 1, lower anterior face height was increased more compared with group 2; the mandibular plane angle increased and the mandible developed mostly in the vertical dimension. While a Class I molar relationship and correction of the overbite and overjet were achieved in both groups, a greater correction of overjet was found in group 1. Retrusion of the upper incisors without extrusion, protrusion, or proclination of the lower incisors, distalization of the upper molars, mesialization and extrusion of the lower molars and mesialization of the mandibular dentoalveolar structures were observed in both groups. Contributions to the correction of overjet and molar relationship were mostly dentoalveolar in both groups.