One Year Assessment of Surgical Outcomes Using Shape Correspondence

OBJECTIVES: To localize and quantify changes after 1 year following surgical correction for Class III malocclusion, using superimpositions of 3D correspondent point models. METHODS: 3D models of 25 patients treated with two jaw surgery and 25 patients treated with maxillary advancement only, were built from Cone-Beam CTs taken pre-surgery (T1), at splint removal (T2) and 1 year post-surgery (T3). Surface models were superimposed through an automated voxel-wise method using the cranial base of the pre-surgery scan as reference. Measurements of longitudinal changes at each anatomic region of interest included 3D corresponding point surface distances and vectors. Vector maps and signed distances color maps were used to visualize rotational displacements and localize the regions of surface remodeling. RESULTS: The dimension of vectors of maxillary advancement, respectively in the maxilla only and two-jaw surgery groups were in average: T1-T2 6.95+/-3.04mm and 7.52+/- 2.86mm; T1-T3 5.58mm +/-2.59mm and 6.96 +/- 2.96mm; T2-T3 -1.01+/- 2.58mm and -0.62 +/- 3.13mm. Between T2-T3: (a) Both groups presented stability of the anterior displacement of the maxilla; however, 52% of maxillary only and 48% of the two-jaw surgery patients presented vertical adaptations of the maxilla >2mm. (b) Chin displacements >2mm occurred in a vertical direction in the maxilla only group (69.5% of the patients) and in an antero-posterior direction in the two jaw surgery group (79%). (c) At least one condyle and rami had >2mm displacement/remodeling in 48% and 68% of the patients in the maxilla only and two jaw surgery groups respectively. CONCLUSION: The maxillary advancement observed at splint removal remained stable 1 year post-surgery in both groups. Displacement in mandibular condyles and rami were greater in the two jaw surgery group. The direction of the post-surgical adaptations in the chin was affected by the type of surgery. Supported by NIH DE017727, DE018962, DE005215.