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Purpose To assess the effect of acid etching (AE) and adhesive systems on the microtensile bond strength of conventional glass ionomer cement (GIC) and a nanofilled composite resin. Materials and methods Specimens of conventional GIC (RIVA, Self-cure, SDI) were prepared in a bipartite Teflon mold and randomly assigned (n=12) to G1- GIC+Single Bond 2 (SB2) (3M-ESPE); G2- GIC+Acid etching (AE) (37% phosphoric acid, Condac, FGM) + SB2; G3- GIC+Single Bond Universal (SBU) (3M-ESPE); and G4- GIC+AE+SBU. The adhesive systems and the composite (Filtek Z350XT, 3M-ESPE) were inserted into the mold. After 7 days stored in a humid environment, the specimens were sectioned into five slices (Isomet 1000, Buehler). Hourglass slices were trimmed and subjected to microtensile bond strength testing (BISCO®; Schaumburg, USA) with 0.5 mm/min crosshead speed. Data were analyzed by two-way ANOVA and the Tukey test (SPSS 17.0, α=5%). Results The microtensile bond strength (MPa) means (standard deviation) were G1=9.46(3.79), G2=6.27(3.21), G3=9.35(3.91), and G4=10.13(3.53). G2 differed significantly from the other groups (p 0.05). There were 83% mixed fractures, 9.5% cohesive and 7.5% adhesive. Conclusion GIC etching promoted higher microtensile bond strength with universal adhesive than with a total-etch adhesive system. Acid etching is not necessary to enhance the universal adhesive bond strength and negatively affected the bond strength of the total-etch adhesive system. Without etching the GIC, there is no difference in microtensile bond strength between the adhesive systems.

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.

Resumen pt: Objeti vo: Caracterizar os pacientes atendidos no programa de manutencao preventi va (MP) e relacionar as necessidades de tratamento apresentadas com os ...

A distribuição das tensões ao longo da estrutura dentária é determinada pela direção, o tipo e a magnitude das cargas que incidem na superfície oclusal e pelas características das estruturas de suporte. Este estudo teve como objetivo analisar, através do Método de Elementos Finitos, a distribuição de tensões na estrutura dentária, em um modelo tridimensional (3D) do primeiro pré-molar superior submetido a diferentes tipos de carregamentos, considerando o esmalte anisotrópico ou isotrópico. A modelagem geométrica foi realizada a partir de uma tomografia computadorizada e as propriedades mecânicas bem como as condições de carregamento foram determinadas no programa de elementos finitos Abaqus®. Cargas axiais e oblíquas foram aplicadas na superfície oclusal do primeiro pré-molar superior nas seguintes condições: I) Carga axial de 30N aplicada simultaneamente nos contatos oclusais A e B e na crista marginal mesial, totalizando 90N; II) Carga axial de 90N no contato da aresta longitudinal mesial da cúspide palatina, simulando um contato excêntrico; III) Carga oblíqua de 45N, com inclinação de 45o no contato oclusal A; IV) Carga oblíqua de 45N, com inclinação de 45o no contato B. Para estimar a possibilidade de falha nas estruturas simuladas, foram analisadas as tensões principais máximas e os valores de tensões de tração comparados aos valores de resistência dos tecidos em estudo. Os resultados mostraram, em todos os modelos, tensões de compressão no lado de aplicação da carga e de tração, no lado oposto à aplicação. As tensões de tração concentraram-se principalmente na região cervical do dente e na inserção óssea alveolar. Os modelos anisotrópicos apresentaram áreas de concentração de tensões menores do que os modelos isotrópicos. Concluiu-se que, os modelos em 3D isotrópicos são satisfatórios para análise de distribuição de tensões em dentes, por serem de modelagem menos complexa e produzirem resultados similares comparados aos modelos anisotrópicos. O esmalte cervical parece ser mais susceptível à fratura devido à maior concentração de tensões nesta região associada à sua composição e características anatômicas indicam maior predisposição à fratura. The direction, type and magnitude of loads on the oclusal surface and also the characteristics of the support structures determines the stress distribution. The aim of this study was to analyze, by the finite element method, the stress distribution on the first superior premolar, in a tridimensional (3D) model subjected to various types of loadings considering the enamel anisotropic or isotropic. The geometric modeling was performed based on a computed tomography (CT) scan. The mechanical properties as well as the loading conditions determined by the Abaqus® finite element program. Axial and oblique loads were applied on the occlusal surface of the first superior premolar in the following conditions: I) 30N axial load applied simultaneously on the occlusal contacts A and B and in the mesial marginal ridge, totaling 90N; II) 90N axial load in the mesial longitudinal edge of the lingual cusp, simulating eccentric contact; III) 45N oblique load with a 45o inclination on theocclusal contact A; IV) 45N oblique load with a 45o inclination on the occlusal contact B. To estimate the possibility of failure in the simulated structures, the maximum principal stress were analyzed and compared to known tensile strength values of the tissues studied. The results showed compression stress on the side in which the load was applied and tensile stress on the opposite side. Tensile stress concentrates mainly in the cervical region of the tooth and in the alveolar insertion bone. Anisotropic models revealed areas of tensile stress concentration smaller than the isotropic models. It was concluded that the isotropic 3D models were suitable for analyzing the stress distribution in teeth, because they are less complex models to build and produced similar results compared to the anisotropic models. The cervical enamel seems to be more susceptible to fracture because of the largest stress concentration on this area, associated with its composition and anatomical characteristics.