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

PURPOSE: This study aimed to investigate changes in sleep-related respiratory parameters before and after orthognathic surgery in patients with skeletal class III malocclusion. METHODS: 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: Delta </= -2.5, -2.5 < Delta < 2.5, and Delta >/= 2.5. Amounts of surgical movement and pre-surgical parameters were compared among the 3 groups. RESULTS: 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 (DeltaREI </= -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). CONCLUSION: There was no significant change in sleep-related respiratory parameters following mandibular setbacks with or without maxillary advancement in this study. TRAIL REGISTERED: This study was retrospectively registered and approved on February 11, 2025, under registration number TCTR20250211002.