Avaliação da cirurgia de avanço mandibular por meio da superposição de modelos tridimensionais

• Autor(a) principal: Motta, Alexandre Trindade Simões da
• Data de Publicação: 2007
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/13988
• topic: CBCT; 3D Models; Mandibular advancement; Tomografia computadorizada; Imagem tridimensional; Avanço mandibular; CNPQ::CIENCIAS DA SAUDE::ODONTOLOGIA::ORTODONTIA

Condyles and rami displacements following mandibular advancement surgery have been described, but these changes and bone remodeling/resorption influence on post-treatment instability are poorly understood at present. Cone beam computed tomography (CBCT) and 3D imaging tools can now overcome conventional methods limitations in assessing surgical displacements. The aim of this study was to assess surgery and short-term post-surgery changes in the position of the condyles, rami and chin with the superimposition of 3D cone-beam CT models. Pre-surgery (T1), 1 week post-surgery (T2), and 6 week post-surgery (T3) CBCT scans were acquired for 20 retrognathic patients (14 females and 6 males, mean age = 27.08 years, range = 13.9-53.7 years) with short or normal face height who underwent a BSSO mandibular advancement. Seven patients also received a genioplasty as an adjunctive procedure. 3D models were built and superimposed through a fully automated voxel-wise method using the cranial base of the pre-surgery scan as reference. After combining the 3 models, anatomic regions of the chin, right and left condyle and ramus were selected and analyzed separately. Within-subject surface distances between T1-T2, T2-T3, and T1-T3 were computed, showing changes with surgery, after splint removal, and the total movement resultant, respectively. Color-coded maps and semi-transparent display of overlaid structures allowed the evaluation of displacement directions. After an antero-inferior chin displacement with surgery in all the cases (>4mm in 87.5%), 25% of the patients showed some kind of posterior movement (< 3mm), and 69% showed an antero-superior movement after splint removal. Comparing T1-T3, an antero-inferior (87.5% of the cases) or only inferior (12.5%) displacement was observed (>4mm in 80%). Considering all directions of displacement, the surface distance differences for the condyles and rami were small: 77.5% of the condyles moved <2mm with surgery (T1-T2), and 90% moved <2mm in the short-term (T2-T3) and in the total evaluation (T1-T3), while the rami showed a <3mm change with surgery in 72.5% of the cases, and a <2mm change in 87.5% (T2-T3) and in 82% (T1-T3). The condyles tended to move latero-posteriorly with surgery compared to a medio-anterior movement between T2-T3. The rami exhibited outward movements with surgery (infero-latero-posterior) and supero-medio-anterior displacements from T2-T3. The displacement tendencies between T1-T3 were medio-postero-superior in the condyles, and supero-latero-anterior in the rami. 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.