Comparable Skeletal and Dental Movements Achieved Using Conventional and Surgery-First Techniques in Class III Patients

Abstract

The surgery-first (SF) approach to orthognathic surgery has been proposed as a more efficient method to correct the dentofacial deformity. This study aimed to evaluate if the magnitude of skeletal and dental changes achieved in Class III patients treated with either conventional orthognathic surgery (COS) or SF techniques differ. A retrospective cohort study of Class III orthognathic surgery patients between January 2006 and May 2020 with available pre- and post-treatment lateral cephalograms was conducted at an academic institution. The primary predictor variable was surgery technique: COS or SF. Assessed outcome variables included cephalometric skeletal parameters: SNA, SNB, ANB, Wits Appraisal, Sn-GoGn, and FMA; and dental parameters: U1-SN, U1-NA (°), U1-NA (mm), L1-NB (°), L1-NB (mm), and overjet. Within-group posttreatment parameters were analyzed with paired t tests. Pretreatment, posttreatment, and between-group parameter changes were analyzed by 2-sided 2-sample independent t tests. Potential covariates, including gender, surgical procedure, previous conventional treatment, extractions (excluding 3rd molars), crowding, and midline discrepancy, were analyzed using Fisher exact tests. Thirty-nine subjects were included in this study: 1) 21 COS (age: 20.9±8.7years) and 2) 18 SF (age: 19.6±5.0years). Cohorts were comparable (P>.05) for all analyzed covariates. COS showed statistically significant increases in L1-GoGn (3.31±6.23°; P=.024), overjet (4.26±3.99mm; P<.001), ANB (3.5±2.79°; P<.001), SNA (3.5±1.85°; P<.001), and Wits Appraisal (3.78±4.97mm; P=.002). SF showed statistically significant increases in L1-GoGn (4.19±4.85°; P=.002), L1-NB (3.08±4.13°; P=.006), L1-NB (0.79±1.35mm; P=.023), overjet (5.82±2.96mm; P<.001), ANB (5.51±3°; P<.001), SNA (4.13±2.38°; P<.001), and Wits Appraisal (5.92±3.42mm; P<.001) and statistically significant decreases in U1-NA (-3.69±7.35°; P=.048) and SNB (-1.38±2.14°; P=.014). There were no statistically significant differences in skeletal or dental parameters between groups when adjusted for pretreatment levels of that parameter. The mean treatment duration was 38months (standard deviation=12.7) in COS and 17.6months (standard deviation=5.2) in SF. The results show that skeletal and dental changes between groups were not statistically different, despite an average 20-month difference in treatment duration. This suggests that either technique can be used to achieve comparable degrees of skeletal and dental movement in Class III patients.