3D Condylar Surface Remodeling following Skeletal Class III Surgery

OBJECTIVES: To localize and quantify condylar surface remodeling following surgical correction for Class III, using superimpositions of 3D virtual surface models.

METHODS: 3D surface models for 40 Class III patients (20 treated by maxillary advancement only and 20 by two jaw surgery) were built from Cone-Beam CT images taken pre-surgery, at splint removal (~6 weeks post-surgery) and at the completion of orthodontic treatment (~1 year post-surgery). Surface models were superimposed through a fully automated voxel-wise method using the cranial base of the pre-surgery scan as reference. Closest point surface distances were computed to quantify condylar surface remodeling during the post-surgical orthodontic treatment. Color maps were used to visualize rotational displacements and localize the regions of surface remodeling.

RESULTS: The condylar surface remodeling was significantly smaller for maxillary surgery only compared to two-jaw surgery patients (p< .01 for both condyles). For maxillary surgery only patients, if the maxillary vertical position changed, the mandibular condyles (left condyle r= 0.77, p<0.001; right condyle r=0.62, p<0.013) tended to rotate anteriorly around the long axis with slight remodeling on the superior surface of the condyles. For patients who had two-jaw surgery, the condyles rotated transversely with the medial pole positioned more forward and laterally. In contrast to the maxillary only group, post-surgical surface remodeling in the two jaw group tended to occur on the medial pole and the posterior surface of the condyles.

CONCLUSIONS: Condylar surface remodeling occurs following orthognathic surgery for treatment of skeletal class III regardless of whether a maxillary advancement only or two jaw procedure is used. However, the amount, location and direction of condylar surface remodeling differs. Future studies are needed to investigate whether condylar remodeling occurs as a physiological adaptation during post-surgical orthodontic treatment or whether it can lead to long term relapse.

Support: NIDCR DE017727 and DE005215.