Effect of proximal segment osteotomy level on mandibular angle changes after intraoral vertical ramus osteotomy: a three-dimensional CBCT study.

This retrospective study aimed to analyze changes in the mandibular angle, based on the ostectomy level of the proximal segment following intraoral vertical ramus osteotomy (IVRO) for mandibular setback in 40 patients with mandibular prognathism, using three-dimensional reconstruction images obtained from cone-beam computed tomography. The ostectomy level of the proximal segment was categorized into two groups based on the distance from the gonion to the ostectomy site: within 5 mm and over 5 mm. A statistically significant increase in the mandibular angle was observed in both hard and soft tissues following IVRO, along with a decrease in both the horizontal and vertical distances from the earlobe to the soft-tissue gonial angle. However, the mandibular angle did not vary significantly with ostectomy level. The gonion moved posteriorly and superiorly in both groups, with no significant differences between the groups, based on the ostectomy level of the proximal segment. These results suggest that while IVRO significantly enhances the aesthetics of the mandibular angle, a 5 mm difference in ostectomy level does not lead to remarkable morphological changes in this region. These findings are clinically relevant for surgical planning, particularly in aesthetic improvements to the lower third of the face.