Positional changes in the mandibular proximal segment after intraoral vertical ramus osteotomy: Surgery-first approach versus conventional approach

Abstract

Objective To compare postoperative positional changes in the mandibular proximal segment between the conventional orthognathic surgery (CS) and the surgery-first approach (SF) using intraoral vertical ramus osteotomy (IVRO) in patients with Class III malocclusion. Methods Thirty-eight patients with skeletal Class III malocclusion who underwent bimaxillary surgery were divided into two groups according to the use of preoperative orthodontic treatment CS group (n = 18) and SF group (n = 20). Skeletal changes in both groups were measured using computed tomography before (T0), 2 days after (T1), and 1 year after (T2) the surgery. Three-dimensional (3D) angular changes in the mandibular proximal segment, condylar position, and maxillomandibular landmarks were assessed. Results The mean amounts of mandibular setback and maxillary posterior impaction were similar in both groups. At T2, the posterior portion of the mandible moved upward in both groups. In the SF group, the anterior portion of the mandible moved upward by a mean distance of 0.9 ± 1.0 mm, which was statistically significant ( p < 0.001). There were significant between-group differences in occlusal changes ( p < 0.001) as well as in overjet and overbite. However, there were no significant between-group differences in proximal segment variables. Conclusions Despite postoperative occlusal changes, positional changes in the mandibular proximal segment and the position of the condyles were similar between CS and SF, which suggested that SF using IVRO achieved satisfactory postoperative stability. If active physiotherapy is conducted, the proximal segment can be adapted in the physiological position regardless of the occlusal changes.

Three-Dimensional Changes in the Mandibular Proximal Segment After Using a Surgery-First Approach in Patients With Class III Malocclusion and Facial Asymmetry

“…5 ). Our results are in line with the findings of a previous study by Jung et al, 21 who used lateral cephalometric analysis to compare the changes in the proximal segment of the mandible in patients treated with SFA and CA. They showed similar positional changes between the 2 groups.…”

“…In addition, several previous studies have been performed to analyze the amount and direction of condylar displacement. 12,[17][18][19][20][21] Although efforts have been made to control the position of the proximal segment to ensure surgical stability, 15,22 these previous studies mostly assessed the condylar positional changes in two-dimensional (2D) radiographs such as lateral cephalograms and 2D reformatted images derived from the computed tomography (CT). Soverina et al, 9 in their systematic review, reported that because all articles described stability using a penultimate time point of "after surgery" and not "after debonding," orthodontic movements and consequent mandibular movements could have influenced cepha-lometric measurements.…”

Incidence and management of condylar resorption after orthognathic surgery: An overview

“…1 Condylar resorption (CR) is an uncommon but well-known clinical condition that can occur after surgical repositioning of the jaws. 2 , 3 It represents the advanced stage of condylar remodeling, irreversibly affecting the temporomandibular joint (TMJ). 3 - 5 As a result of mechanical load, the adaptive mechanisms that normally allow to balance bone resorption and bone formation on the condylar surface are completely lost, resulting in morphological alterations of the condylar structure.…”

“… 6 Referring to orthognathic surgery, all osteotomies can lead to CR, which can occur in both mono-maxillary and bi-maxillary surgery. 2 , 12 Bilateral sagittal split osteotomy (BSSO) and/or Le Fort I osteotomy can modify the mechanical forces on the condylar surface, resulting in CR. 12 …”

“…6 Referring to orthognathic surgery, all osteotomies can lead to CR, which can occur in both monomaxillary and bi-maxillary surgery. 2,12 Bilateral sagittal split osteotomy (BSSO) and/or Le Fort I osteotomy can modify the mechanical forces on the condylar surface, resulting in CR. 12 Several studies have focused on condylar alterations after orthognathic surgery, and some systematic reviews (SRs) aimed to determine the most crucial risk factors for CR.…”