[Compensation of upper first molar in skeletal class Ⅲ patients treated with orthodontic-surgical treatment]

Objectives: To investigate the compensation of upper first molar in adult skeletal class Ⅲ patients. Methods: The sample consisted of 48 skeletal class Ⅲ patients with orthodontic-surgical treatment from February 2011 to January 2015 in Peking University School and Hospital of Stomatology. They were allocated into 2 groups based on extraction, 28 patients in extraction group and 22 patients in non-extraction group. Dental casts were taken before and after treatment, and all the casts were scanned with a computer-assisted three-dimensional (3D) scanning system. Acquired 3D data were analyzed by Rapidform 2006. The tip and torque of the upper first molar were measured and analyzed. Results: The tip and torque of the upper first molar in the skeletal class Ⅲ patients after treatment had no difference between extraction group and non-extraction group (P=0.150, P=0.144). The torque of upper first molar in extraction group [-3.32° (-5.10°, 1.16°)] before treatment was bigger than that in non-extraction group [-6.94° (-13.06°, -0.42°)] (P=0.005), and the inclination of upper first molar in extraction group was more obvious. Conclusions: In skeletal class Ⅲ patients, the upper first molar inclined buccally to compensate the discrepancy and extraction was usually necessary for decompensation.