RESUMO
It has been suggested that third molars increase mandibular fragility because they do not contribute to its strength. For ethical reasons, a human study design that would permit the elucidation of this interference is not possible. This study evaluated the impact of the presence of erupted third molars on the mandibular angle of resistance when submitted to trauma. A three-dimensional (3D) mandibular model was obtained through finite element methodology using computed tomography (CT) with the geometry and mechanical properties to reproduce a normal mandibular structure. Human mandibles with no, one or two erupted third molars were evaluated. Whenever the third molar was present there was a greater concentration of tensions around the cervical part of its alveolus. Approximated Von Mises equivalent stress of the third molar region was 107.035 MPa in the mandible with teeth and 64.6948 MPa in the mandible without teeth. In the condylar region it was 151.65 MPa when the third molar was present and 184.496 MPa when it was absent. The digital models created proved that the mandibular angle becomes more fragile in the presence of third molars. When they are absent the energy concentrates on the lateral e posterior aspect of the condylar neck.
Assuntos
Queixo/lesões , Mandíbula/fisiopatologia , Traumatismos Mandibulares/fisiopatologia , Dente Serotino , Adulto , Fenômenos Biomecânicos , Queixo/diagnóstico por imagem , Queixo/fisiopatologia , Simulação por Computador , Tomografia Computadorizada de Feixe Cônico , Análise do Estresse Dentário , Análise de Elementos Finitos , Humanos , Processamento de Imagem Assistida por Computador , Imageamento Tridimensional , Masculino , Mandíbula/diagnóstico por imagem , Traumatismos Mandibulares/diagnóstico por imagem , Modelos Biológicos , Dente Serotino/diagnóstico por imagemRESUMO
OBJECTIVE: The purpose of this study is to estimate how is the magnitude of the impact of a mandibular third molar on the mandibular angle stiffness. STUDY DESIGN: It was performed a literature search on whole MEDLINE and LILACS data base to find articles that match the following inclusion criteria: cohort studies presenting data on patients with mandibular fractures and third molars; that had a similar angle fracture definition; and that present data available to be cross-classified in a statistic analysis. RESULTS: The sample was composed by 4 studies, involving 2533 patients from USA, Nigeria, Germany and Jordan, evaluated between 1976 and 2001. The analysis of the sample shows a relative risk for a mandibula to fracture, comparing patients with and without third molars, ranging from 1,18 to 2,25. The data of the sample was grouped because of the homogeneity of the articles methods. The estimated relative risk across the 4 studies was 1,94 (95% CI 1,6 - 2,35). CONCLUSIONS: The presence of a third molar may double the risk of an angle fracture of the mandible to occur. Even with this data, the present study cannot support conditions related to the third molar that may affect this impact. Further studies are necessary to discuss the true indication of removal of these teeth as a prophylactic measure in population groups more predisposed to fracture.