ABSTRACT
Chin cup is a orthopedic appliance for treating growing skeletally C1 III patients. The amount of chin forward movement in addition to morphologic changes in bony structure. Determines the final profile of treated patients. The aim of this study was to evaluate the amount of morphologic changes of symphysis after chin cup therapy in skeletally C1 III patients. In this clinical trial, twenty eight cephalometries before and after chin cup therapy of 14 skeletally C1 III patients were analyzed. Landmarks introduced by Ricketts were determined to evaluate the symphysis individually were evaluated and analyzed. Data were analyzed by paired t and pearson tests with P<0.05 as the level of significance. The results showed that the height of symphysis increased after treatment [P=0.02], but its depth decreased [P=0.04]. The sysmphysis turned down and back. These findings suggest that in C1 III malocclusions with a prognathic mandible, chin cup therapy creates changes in the horizontal dimention of symphysis morphology, which improves the C1 III profile. If the patient isn't a vertical grower, vertical changes of symphysis would be desired. In addition, changes in the vertical dimension of the mandible [body and ramus] could be observed as a backward and downward rotation