Three-Dimensional Analysis of Transverse Width of Hard Tissue and Soft Tissue After Mandibular Setback Surgery Using Intraoral Vertical Ramus Osteotomy: A Retrospective Study

Abstract

Some clinicians are concerned that if an intraoral vertical ramus osteotomy (IVRO) is used to position the mandible posteriorly, the proximal segments should be positioned laterally to the distal segment, which could increase the transverse mandibular width, leading to esthetically unfavorable results. This study investigated short- and long-term postoperative transverse mandibular width changes in the soft and hard tissue after IVRO for mandibular prognathism. The study comprised 44 patients who were treated with mandibular setback surgery using an IVRO. They were categorized into either the facial symmetry group or facial asymmetry group based on their preoperative levels of chin top deviation. Three-dimensional cone-beam computed tomography images were obtained at the preoperative, 1-month postoperative, and 12-month postoperative stages, designated as T1, T2, and T3, respectively. We set hard tissue width 1 (HW1) and hard tissue width 2 (HW2) as the sum of the distance at the bilateral ends of the angle and ramus, respectively, and set soft tissue width 1 (SW1) and soft tissue width 2 (SW2) as the sum of the distance at the bilateral ends of the soft tissue angle and ramus, respectively. Compared with the value at T1, the HW1 value increased by 8.16% (P<.05) and HW2 increased by 4.39% (P>.05) at T2; HW1 increased by 4.35% (P<.05) and HW2 increased by 2.95% (P>.05) at T3. Compared with the value at T1, the SW1 value increased by 2.49% and SW2 increased by 2.50% at T2; however, SW1 decreased by 0.85% and SW2 increased by 0.37% at T3. The soft tissue variations between T1 and T2, as well as between T2 and T3, were statistically significant. However, no significant difference was found between T1 and T3 (P>.05). No difference between the facially symmetrical and asymmetrical groups was found over time for soft and hard tissues (P>.05). Notably, IVRO does not seem to impact the transverse facial profile and enables reliable prediction of the esthetic results of surgery.