Patients with Class II skeletal malocclusion and high occlusal plane angle are more susceptible to TMJ osteoarthritis. The objectives of this study were to evaluate condylar positional changes and remodeling after bimaxillary surgical advancement and to assess the outcomes of articular disc repositioning, using longitudinal 3D volume voxel-wise superimpositions one year following surgery.
Twenty-seven patients treated with maxillo-mandibular advancement had CBCTs taken before surgery (T1), immediately following surgery (T2) and at one-year follow-up (T3). Ten patients had no TMJ abnormality and received maxillo-mandibular advancement only (MMA). Seventeen patients had diagnosis of articular disc displacement before surgery and received maxillo-mandibular advancement with TMJ disc repositioning simultaneously (MMA_disc_rep).
Result: Presurgery and postsurgery 3D virtual models were registered on the surface of the cranial base. The location, direction and magnitude of changes in the condyles between superimposed models was displayed and quantified by graphical overlay and 3D color-coded surface distance maps. Immediately after surgery, all MMA patients had condylar displacements >1.5mm in either posterior, superior or medio-lateral direction, while MMA_disc_rep patients presented more marked anterior, inferior and medio-lateral condylar displacements. At 1-year post-surgery, patients in the MMA group showed >1.5mm bone resorption of the condylar superior surface in 15% of the cases, anterior (25%), posterior (10%), medial (25%) and/or lateral poles (25%). MMA_disc_rep patients had >1.5mm condylar bone resorption at superior (29.4%), anterior (8.8%), posterior (20.6%), medial (23.5%) and/or lateral (38.2%) surfaces and bone apposition at superior (26.4%), anterior (23.4%), posterior (29.4%), medial (5.9%) and/or lateral (38.2%) surfaces.
Conclusion: Post-surgical adaptations tended to compensate displacements with surgery in both groups. One year after surgery, mild condylar resorptive changes (post-surgical condylar adaptations) were observed in both groups, although articular disc repositioning facilitated bone overgrow in localized condylar regions.