Long-term three-dimensional condylar remodeling during presurgical orthodontics and after orthognathic surgery of mandibular retrognathia with high mandibular plane angle

Objectives Patients with high mandibular plane facial morphology are the most dominant facial type who experience TMJ abnormalities with resultant condylar resorption, affecting the orthodontic and orthognathic treatment outcomes. The study aimed to quantitatively assess the three-dimensional condylar remodeling during the presurgical orthodontics and after orthognathic surgery of the retrognathic mandible with a high mandibular plane angle. The study also investigated the correlation between the resultant remodeling based on the hypothesis that condylar resorption following orthognathic surgery is a part of a progressive presurgical resorption process. Materials and methods The study included adults with mandibular retrognathism and high mandibular plane angle who have computed tomography scans (CT) obtained before any treatment (T0), after completion of presurgical treatment before surgery (T1), and at long-term follow-up after surgery (T2). DICOM of CT scan was gathered and processed using ITK-SNAP and 3D Slicer software. The interval between T0 and T1 was represented as a presurgical phase, while between T1 and T2 was defined as a postsurgical phase (T1-T2). Results Twenty-five patients (50 condyles) were included with a mean age of 23 ± 3.2 years. The mean of the follow-up during the presurgical phase was 19.8 ± 7.1 months and 15.5 ± 5.5 months during the postsurgical phase. The condylar volume during the presurgical phase (T0-T1) was relatively stable (− 3.3 ± 37.2mm 3 ). However, during the postsurgical phase (T1-T2), the volume was significantly reduced − 113.8 ± 98.3mm 3 ( P < 0.001). Localized condylar surface resorption during the postsurgical phase was significantly higher than during the presurgical phase ( P < 0.05). No correlation was found between the localized condylar surface remodeling during the presurgical and postsurgical phases. However, a negative statistically significant correlation existed between the overall condylar volume changes during the presurgical and postsurgical phases ( r = 0.502, P < 0.001). Conclusion Significant condylar resorption following orthognathic surgery of the retrognathic mandible with a high mandibular plane angle might occur regardless of the presurgical status of the condyle. Clinical relevance The study provided an evidence to be discussed with the patients and considered throughout the treatment of mandibular retrognathia with high mandibular plane angle.