Edition V15N01 | Year 2010 | Editorial Online Article | Pages 45 to 48
Objectives: To assess surgery and short-term post-surgery changes in the position of the condyles, rami and chin after mandibular advancement.
Methods: Pre-surgery (T1), 1 week postsurgery (T2), and 6 weeks post-surgery (T3) CBCT scans were acquired for 20 retrognathic patients with short or normal face height. Three-dimensional models were built and superimposed through a fully automated voxel-wise method using the cranial base of the pre-surgery scan as reference. Anatomic regions of interest were selected and analyzed separately. Withinsubject surface distances between T1-T2, T2-T3, T1-T3 were computed. Color-coded maps and semi-transparent display of overlaid structures allowed the evaluation of displacement directions. Results: After an antero-inferior chin displacement with surgery in all cases (>4 mm in 87.5%), 25% of the patients showed some kind of posterior movement (<3 mm), and 69% showed an antero-superior movement after splint removal. Comparing T1-T3, an anteroinferior (87.5% of the cases) or only inferior (12.5%) displacement was observed (>4 mm in 80%). Considering all directions of displacement, the surface distance differences for the condyles and rami were small: 77.5% of the condyles moved <2 mm with surgery (T1-T2), and 90% moved <2 mm in the short-term (T2-T3) and in the total evaluation (T1-T3), while the rami showed a <3 mm change with surgery in 72.5% of the cases, and a <2 mm change in 87.5% (T2-T3) and in 82% (T1-T3). Conclusions: Expected displacements with surgery were observed and post-surgery changes suggested a short-term adaptive response toward recovery of condyle and ramus displacements. The changes on the chin following splint removal suggested an acceptable adaptation, but with considerable individual variability. Cone-Beam Computed Tomography, Image processing, Computer-assisted surgery, Computer simulation, Orthodontics, Oral surgery,