Exploring long-term changes and influencing factors of the upper airway in patients with a skeletal Class II relationship after mandibular advancement with maxillary setback surgery: A comprehensive 2-year follow-up investigation.

INTRODUCTION: The objective of this study was to investigate the 2-year postoperative change and influencing factors of the upper airway after mandibular advancement with maxillary setback surgery for patients with a skeletal Class II relationship.

METHODS: Fifty-seven participants who underwent mandibular advancement with maxillary setback surgery were enrolled consecutively. Cone-beam computed tomography was performed preoperatively, 3 months postoperatively (T1), and 2 years (T2) postoperatively. All parameters were measured using Dolphin Imaging software (Dolphin Imaging and Management Solutions, Chatsworth, Calif).

RESULTS: The total volume (V), minimum cross-sectional area (CSAmin ), and glossopharynx increased significantly in both the short-term (V, 13.33%; CSAmin , 33.03%; glossopharynx, 26.73%) and long-term (V, 10.19%; CSAmin , 23.18%; glossopharynx, 18.27%) after the surgery. Mandibular advancement, mandibular width increase, preoperative CSAmin , and body mass index (BMI) significantly affected 2-year postoperative V increases. Mandibular advancement and BMI significantly affected 2-year postoperative glossopharynx increases. Backward movement of point PNS may lead to a reduction of the nasopharynx; however, downward movement of point PNS, upward movement of point A, and increased maxillary width may compensate for this effect by increasing the likelihood of the nasopharynx opening. Furthermore, mandibular body length at T1 is positively associated with relapse rate ([T2 - T1] / T1) of V and CSAmin .

CONCLUSIONS: Mandibular advancement amount, mandibular width increase, preoperative CSAmin , and BMI are the 4 factors for long-term V changes. Patients with a longer mandibular body length might have a lower relapse rate.