Three-dimensional evaluation of skeletal stability after surgery-first bimaxillary surgery for class III asymmetry in 70 consecutive patients

Skeletal stability after orthognathic surgery is essential for positive treatment outcome. This study evaluated the stability of osteotomy segments after surgery-first bimaxillary surgery for class III asymmetry. Seventy adults with class III asymmetry consecutively corrected through surgery-first Le Fort I and bilateral sagittal split osteotomies were investigated. Cone-beam computed tomography before treatment (T0), 1-week after surgery (T1), and after all treatment (T2, ≥1-year after surgery) was used to assess surgical movement (T0 to T1) and skeletal stability (T1 to T2) regarding the translation and rotation of the maxillary, mandibular distal, and proximal segments. At T1, the maxillary segment had moved forward and upward, turned to the deviated side, and rotated downward (all P < 0.01). The distal segment of mandible 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). The opposite proximal segment had moved upward and tilted to the deviated side (both P < 0.01). At T2, significant relapse occurred in the mandible. The distal segment moved forward and upward and rotated upward (all P < 0.001). The deviated proximal segment moved upward, tilted to the opposite side, and rotated upward (all P < 0.001). The opposite proximal segment moved upward and tilted to the deviated side (both P < 0.01). Clinically significant relapse of class III asymmetry was discovered on the mandibular distal and opposite proximal segments.