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Skeletal Stability and Occlusal Plane Changes in Class III Orthognathic Surgery: Comparison of Clockwise and
Reza Tabrizi1, Samin Ghaffari1, Shervin Shafiei1
1School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Oral and Maxillofacial Department, Hospital Clinic de Barcelona, Barcelona, Spain; Department of Oral and Maxillofacial Surgery, Massachusetts General Hospital, and Harvard School of Dental Medicine, Boston, MA, USA.
Occlusal plane rotation in Class III deformity surgery impacts rotational relapse but not linear skeletal relapse. While significant, the absolute magnitude of differences was clinically minor, suggesting careful planning is key.
Area of Science:
- Orthodontics and Maxillofacial Surgery
- Skeletal Deformity Correction
- Orthognathic Surgery Outcomes
Background:
- Occlusal plane (OP) rotation is common in bimaxillary Class III deformity correction.
- Its independent effect on surgical stability is not well understood.
Purpose of the Study:
- To investigate the association between occlusal plane rotation direction and skeletal stability after bimaxillary orthognathic surgery for Class III deformity.
Main Methods:
- Prospective cohort study of 80 adults with skeletal Class III deformity undergoing bimaxillary surgery.
- Patients categorized by OP angle change (clockwise vs. counterclockwise rotation).
- Cone-beam computed tomography (CBCT) used for cephalometric analysis at baseline, immediately post-op, and 24 months post-op.
Main Results:
- Greater OP relapse occurred with counterclockwise OP rotation compared to clockwise rotation.
- Sagittal relapse at point B was also significantly greater in the counterclockwise rotation group.
- Multivariable analysis indicated OP change primarily predicts OP relapse, not linear skeletal relapse.
Conclusions:
- OP rotation direction correlates with rotational relapse but doesn't solely determine linear skeletal relapse.
- Observed differences in relapse were statistically significant but clinically minor.
- OP rotation should be integrated into planning but not overemphasized as a predictor of instability.
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