# Three-dimensional volumetric changes in TMJ space following mandibular advancement surgery in skeletal Class II patients: a CBCT analysis

## TL;DR

This study used 3D imaging to show how jaw surgery changes the space in the temporomandibular joint in patients with a specific jaw condition.

## Contribution

The study provides new 3D volumetric data on TMJ space changes after mandibular advancement surgery in skeletal Class II patients.

## Key findings

- Anterior joint space increased after surgery but slightly decreased after 12 months.
- Posterior and medial joint spaces decreased significantly after surgery.
- Volumetric changes were maintained 12 months post-surgery with some relapse.

## Abstract

The aim of the present study was to assess three-dimensional volumetric changes in the temporomandibular joint (TMJ) space after mandibular advancement surgery in skeletal Class II cases with retrognathic mandibles. The null hypothesis for this study posited that there would be no statistical changes after orthognathic surgery.

A retrospective study was conducted on 30 cone-beam computed tomographic (CBCT) records of skeletal Class II patients with retrognathic mandibles who were treated with bilateral sagittal split osteotomy (BSSO) for mandibular advancement of 6-8 mm. Volumetric assessments of joint space were performed pre-operative (T0), one-week post-operative (T1), and 12-month post-operatively (T2).

The mean anterior joint space exhibited an increase from 612.37 mm3 at T0 to 876.67 mm3 at T1, followed by a slight reduction to 862.4 mm3 at T2. Conversely, the posterior joint space diminished from 861 mm3 at T0 to 736.27 mm3 at T1 and further to 653.07 mm3 at T2. The medial joint space experienced an increase from 525.83 mm3 at T0 to 850.93 mm3 at T1, before declining to 596.77 mm3 at T2. The lateral joint space showed a decrease from 951 mm3 at T0 to 762 mm3 at T1, subsequently rising to 918.7 mm3 at T2. Strong positive correlation coefficients (approaching 1) were observed in the majority of the T1 and T2 comparisons (p < 0.05).

Significant volumetric changes were observed in the TMJ space after mandibular advancement surgery for retrognathism. The changes were maintained even 12 months after surgery, with a slight relapse.