Is There a Difference in Stability After Intraoral Vertical Ramus Osteotomy Between Vertically High-Angle and Normal-Angle Patients?

Abstract

Few studies have evaluated the relapse pattern of intraoral vertical ramus osteotomy (IVRO) for the correction of mandibular prognathism with a high angle. The aim of this study was to measure the association between vertical facial types (high and normal mandibular plane angle) and relapse after IVRO for the management of mandibular prognathism. The retrospective cohort study sample (skeletal Class III patients) was divided into 2 groups according to the angle of the sella-nasion plane relative to the mandibular plane (SN-MP) at the initial examination. Lateral cephalograms were analyzed for the predictor (facial type) and outcome (cephalometric changes over time) variables before surgery, 7days after surgery, and 12months after surgery. The 2 groups were matched for sample size (n= 20 in each). Data were analyzed using repeated-measures analysis of variance with Bonferroni correction. The normal-angle group (group N, SN-MP from 27° to 37°) and high-angle group (group H, SN-MP >37°) were not significantly different in terms of gender and age at the initial examination. Seven days after surgery, the mandibles in group H moved 2.5mm more superiorly than those in group N(P=.013); consequently, the amount of overbite correction in group H was approximately 2mm greater than that in group N (P= .002). Nevertheless, 12months after surgery, there was no statistically significant difference in relapse of the maxilla and mandible between the 2 groups. In the 2 groups, the mandible moved approximately 0.7mm superiorly during retention. These findings suggest that IVRO is a clinically acceptable and stable treatment modality for mandibular prognathism with a high angle.