# A prospective cohort study on effects of mandibular setback with or without maxillary advancement for skeletal class III malocclusion on sleep-related respiratory parameters

## TL;DR

This study found that orthognathic surgery for skeletal class III malocclusion did not significantly change sleep-related breathing parameters in patients.

## Contribution

The study provides new evidence on the effects of mandibular setback and bimaxillary surgery on sleep-related respiratory outcomes.

## Key findings

- No significant changes in sleep-related respiratory parameters were observed after surgery.
- Pre-operative Epworth Sleepiness Scale scores correlated with changes in respiratory event index and blood oxygen levels.
- Patients with a significant decrease in respiratory event index had higher pre-operative values.

## Abstract

This study aimed to investigate changes in sleep-related respiratory parameters before and after orthognathic surgery in patients with skeletal class III malocclusion.

Adults with skeletal class III malocclusion and treated with isolated mandibular setback or bimaxillary surgery (maxillary advancement and mandibular setback) were recruited. Sleep-related respiratory parameters were obtained with type III sleep study. Epworth Sleepiness Scale (ESS) was also recorded. The pre- and post-operative (6 months) data were compared. Correlations between these changes and pre-operative characteristics were analyzed. Subjects were categorized into three groups based on changes in the respiratory event index (REI) and 3% oxygen desaturation index: Δ ≤ -2.5, -2.5 < Δ < 2.5, and Δ ≥ 2.5. Amounts of surgical movement and pre-surgical parameters were compared among the 3 groups.

Thirty patients with an average age of 25.4 ± 5.0 years were recruited. Eleven patients underwent isolated mandibular setbacks while nineteen received bimaxillary surgery. Pre- and post-operative sleep-related respiratory parameters were not significantly different in the total samples, and when analyzed separately according to surgical procedures. Pre-operative ESS were correlated with the changes in REI (p = 0.01), average blood oxygen levels (p = 0.01), and snoring percentage (p = 0.04). Additionally, this study found that patients with a significant decrease in REI (ΔREI ≤ -2.5) after surgery had significantly higher pre-operative REI (6.2 events/hour) compared to those with minor REI changes (2.6 events/hour).

There was no significant change in sleep-related respiratory parameters following mandibular setbacks with or without maxillary advancement in this study.

This study was retrospectively registered and approved on February 11, 2025, under registration number TCTR20250211002.