Three-Dimensional Evaluation of Skeletal Stability after Surgery-First Bimaxillary Surgery for Class III Asymmetry in 70 Consecutive Patients

Abstract

Abstract Background This study (1) evaluated the stability of the maxillary and mandibular proximal and distal segments after surgery-first bimaxillary surgery for class III asymmetry and (2) determined whether the stability of a given mandibular segment was related to the movement of any segment during surgery or postsurgical stability of any other segment. Methods Seventy adults with class III asymmetry consecutively corrected through surgery-first Le Fort I osteotomy and bilateral sagittal split osteotomy were investigated. Cone-beam computed tomography imaging performed before treatment (T0), 1-week after surgery (T1), and after all treatment (T2, ≥1-year after the surgery) was used to assess skeletal movement during surgery (T0 to T1) and postsurgical skeletal stability (relapse, T1 to T2) regarding the translation and rotation of the maxillary, mandibular distal, and proximal segments. Stepwise regression was performed to evaluate the relationship between the stability of a given mandibular segment and the movement of any segment during surgery or postsurgical stability of any other segment. Results At T1, the distal segment had moved forward and upward and rotated upward (all p < 0.001). The deviated proximal segment had moved upward, tilted to the opposite side, and rotated upward (all p < 0.001) and the opposite proximal segment had moved upward (p < 0.001) and tilted to the deviated side (p < 0.01). Sagittal relapse of the distal segment was mainly related to the sagittal instability of the deviated proximal segment (p = 0.001) and pitch rotation during surgery of the opposite proximal segment (p < 0.01). The roll relapse of the opposite proximal segment was mainly related to the vertical movement during surgery of the deviated proximal segment (p < 0.001) and transverse instability of the distal segment (p < 0.01). Conclusions Clinically significant relapse of class III asymmetry was discovered on the mandibular distal and opposite proximal segments and was mainly related to the movement of the deviated proximal segment during and after surgery.