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The combined use of silane and solvated bonding agents on the bond strength to glass-fibre posts was investigated. A model Bis-GMA/HEMA adhesive was formulated with no solvent, 30% of ethanol or 80% of acetone. The surfaces of rectangular-shaped posts were silanated or not and one of the agents was applied, except for the control group. Cylinders of resin cement (RelyX ARC, 3M ESPE, Saint Paul, MN, USA) were built-up on the surfaces (n = 20) and submitted to shear testing. All groups showed higher bond strengths when the surfaces were silanated. When no silanization was carried out, the use of bonding agents, either solvated or non-solvated, increased the bond strengths. All groups treated with both silane and bonding agent showed higher bond strengths than the group that was only silanated. Control and ethanol-based adhesives were similar, whereas the acetone-based agent yielded higher bond strengths. Adhesive failures were predominant. Combination of silane and adhesive enhanced the bond to fibre posts.

To evaluate the effects of different levels of vertical misfit between implant and bar framework on distribution of static stresses in an overdenture-retaining bar system using finite element analysis.A 3D finite element model (11,718 elements and 21,625 nodes) was created and included two titanium implants and a bar framework placed in the medial region of the anterior part of a severely reabsorbed-jaw. All materials were presumed to be linear elastic, homogenous, and isotropic. Mechanical simulation software (NEiNastran 9.0) was used, where displacements were applied on the end of the bar framework to simulate the closure of the vertical misfits (5, 25, 50, 100, 200, and 300 μm) after tightening of the screws. Data were qualitatively evaluated using Von Mises stress given by the software.The models showed stress concentration in cortical bone, corresponding to the cervical part of the implant, and in cancellous bone, corresponding to the apical part of the implant; however, in these regions few changes were observed in stress to the misfits studied. While in the bar framework, retaining-screw neck, and implant platform, a considerable stress increase proportional to the misfit amplification was observed.The different levels of vertical misfit did not considerably influence the static stress levels in the peri-implant bone tissue; however, the mechanical components of the overdenture-retaining bar system are more sensitive to lack of passive fit.

To compare stress distribution between a fractured maxillary central incisor restored with direct composite resin only (CR) or associated with different post materials, using finite element analysis.A three-dimensional model of a sound maxillary central incisor and supporting structures was constructed, using data from the dental literature. Changes were made in the crown region to create a tooth with a restored crown fracture. A composite resin restoration only and restorations associated with different tapered post systems (glass fibre, carbon fibre, titanium and zirconia ceramic) were also evaluated, resulting in six experimental models. A static chewing pressure of 2.16Nmm(-2) was applied to two areas of the palatal surface of the tooth. Stress distribution was analysed under a general condition and in the structures of the models separately.The maximum stresses were concentrated as follows: at the cemento-enamel junction in the model with a sound maxillary central incisor, restored with CR and with a composite resin restoration associated with fibre posts; in the enamel at the post-enamel interface on the palatal surface of the model with a titanium post; and in the post of the model with zirconia ceramic post.None of the restorations evaluated was able to recover the stress distribution of the sound tooth. The models restored with composite resin associated with a glass or carbon fibre post had similar stress distributions to that of the model restored with CR. The different post materials were shown to have a substantial influence on stress distribution, with less stress concentration when fibre posts were used.