ABSTRACT
OBJECTIVE: To investigate the effect of endodontic instrumentation on fracture susceptibility of root dentin using experiments and stress analysis. METHODS: Root canals of lower premolars were enlarged with different tapers. After, teeth were cut into 2-mm sections. A metal rod of the same taper was pushed through the center of the sections using a universal test system to fracture them. The fracture load was determined from the peak load on the load-displacement curve. To determine fracture-causing stress, an axisymmetric FE model was created. An analytical solution was developed to understand the relationship between fracture load, geometrical and material parameters. RESULTS: For the same taper, increased root canal diameter did not lead to reduced fracture load. Both analytical and FE solutions showed positive linear relationship between fracture load and enlarged root canal diameter. The hoop stress was maximum at inner surface of enlarged root canal and reduced with increasing radial distance from the center. Bending of sections introduced further nonuniform stresses along the depth. Predictions for the fracture load based on the maximum hoop stress were closest to experimental values; however, account must be taken of the variation in fracture stress of dentin along the root length. Significance Our results rejected the hypothesis that fracture load of root dentin sections reduced with endodontic instrumentation size. However, the stress distributions in whole endodontically treated teeth are more complicated. Thus, caution is necessary when using thin root sections to investigate the effect of endodontic instruments on vertical root fracture.
Subject(s)
Tooth Fractures , Tooth, Nonvital , Bicuspid , Dental Pulp Cavity , Dentin , Humans , Root Canal Preparation , Root Canal TherapyABSTRACT
A presença de diastemas ântero-superiores pode influenciar negativamente os aspectos estético e psicológico do indivíduo. O objetivo deste estudo é apresentar um relato de caso clínico em que foi realizado o fechamento de diastemas ântero- -superiores com restaurações em resina composta, utilizando a técnica da barreira palatina e seu acompanhamento por dois anos. Diante do planejamento e terapia executados no caso clínico apresentado, pode-se concluir que a técnica restauradora utilizando resinas compostas e barreira palatina, quando corretamente indicada, pode ser considerada uma alternativa de tratamento bastante satisfatória no fechamento de diastemas e na reanatomização de dentes por ser uma técnica simples, de baixo custo e por melhorar a estética do sorriso preservando a estrutura dental hígida. O repolimento anual está indicado para a preservação da cor das restaurações.
Anterior diastema may influence negatively the esthetics and psychological aspects of an individual. This study goal is to present a clinical report in which there was restorations of multiple anterior diastema with composites, using the palatine barrier technique and its two year follow-up. Considering the therapy that was planned and executed on this report, we may conclude that the restorative technique using composites and palatine barrier, when correctly indicated, can be considered a satisfactory treatment alternative for diastema restoration due to its simple execution, low cost and smile esthetics improvement preserving tooth structure. Annual repolishing is indicated for color preservation of the restorations.
ABSTRACT
The aim of this study was to compare the areas of stress concentration in a three-dimensional (3D) premolar tooth model with anisotropic or isotropic enamel using the finite element method. A computed tomography was imported to an image processing program to create the tooth model which was exported to a 3D modeling program. The mechanical properties and loading conditions were prescribed in Abaqus. In order to evaluate stresses, axial and oblique loads were applied simulating realistic conditions. Compression stress was observed on the side of load application, and tensile stress was observed on the opposite side. Tensile stress was concentrated mainly in the cervical region and in the alveolar insertion bone. Although stress concentration analyses of the isotropic 3D models produced similar stress distribution results when compared to the anisotropic models, tensile stress values shown by anisotropic models were smaller than the isotropic models. Oblique loads resulted in higher values of tensile stresses, which concentrate mainly in the cervical area of the tooth and in the alveolar bone insertion. Anisotropic properties must be utilized in enamel stress evaluation in non-carious cervical lesions.
