14 research outputs found
Biomechanical behavior of cavity configuration on micropush-out test : a finite-element-study
Objective: The objective of this study was to simulate the micropush-out bond strength test from a biomechanical point of view. For this purpose, stress analysis using finite element (FE) method was performed. Study design: Three different occlusal cavity shapes were simulated in disc specimens (model A: 1.5 mm cervical, 2 mm occlusal diameter; model B: 1.5 mm cervical, 1.75 mm occlusal diameter; model C: 1.5 mm cervical, 1.5 mm occlusal diameter). Quarter sizes of 3D FE specimen models of 4.0Ă—4.0Ă—1.25 mm3 were constructed. In order to avoid quantitative differences in the stress value in the models, models were derived from a single mapping mesh pattern that generated 47.182 elements and 66.853 nodes. The materials that were used were resin composite (Filtek Z250, 3M ESPE), bonding agent (Adper Scotchbond Multi-Purpose, 3M ESPE) and dentin as an isotropic material. Loading conditions consisted of subjecting a press of 4 MPa to the top of the resin composite discs. The postprocessing files allowed the calculation of the maximum principal stress, minimum principal stress and displacement within the disc specimens and stresses at the bonding layer. FE model construction and analysis were performed on PC workstation (Precision Work Station 670, Dell Inc.) using FE analysis program (ANSYS 10 Sp, ANSYS Inc.). Results: Compressive stress concentrations were observed equally in the bottom interface edge of dentin. Tensile stresses were observed on the top area of dentin and at the half of lower side of composite under the loading point in all of the FE models. Conclusions: The FE model revealed differences in displacement and stress between different cavity shaped disc specimens. As the slope of the cavity was increased, the maximum displacement, compressive and tensile stresses also increased
Comparative evaluation between glass and polyethylene fiber reinforced composites : a review of the current literature
Fiber reinforced composite (FRC) is a promising class of material that gives clinicians alternative treatment options. There are many FRC products available in the market based on either glass or polyethylene fiber type. The aim of this study was to present a comparison between glass and polyethylene fiber reinforced composites based on available literature review. A thorough literature search, with no limitation, was done up to June 2017. The range of relevant publications was surveyed using PubMed and Google Scholar. From the search results, articles related to our search terms were only considered. An assessment of these articles was done by two individuals in order to include only articles directly compare between glass and polyethylene FRCs. The search terms used were ?fiber reinforced dental composites? and ?glass and polyethylene fibers in dentistry?. The search provided 276 titles. Full-text analysis was performed for 29 articles that met the inclusion criteria. Most were laboratory-based research with various test specimen designs prepared according to ISO standard or with extracted teeth and only three articles were clinical studies. Most of studies (n=23) found superior characteristics of glass FRCs over polyethylene FRCs. Significant reinforcement differences between commercial glass and polyethylene fiber reinforced composites were found
Immediate repair bond strength of fiber-reinforced composite after saliva or water contamination
Purpose: This in vitro study aimed to evaluate the shear bond strength
(SBS) of particulate filler composite (PFC) to saliva- or
water-contaminated fiber-reinforced composite (FRC).Materials and
Methods: One type of FRC substrate with semi-interpenetrating polymer
matrix (semi-IPN) (everStick C&B) was used in this investigation. A
microhybrid PFC (Filtek Z250) substrate served as control. Freshly cured
PFC and FRC substrates were first subjected to different contamination
and surface cleaning treatments, then the microhybrid PFC restorative
material (Filtek Z250) was built up on the substrates in 2-mm increments
and light cured. Uncontaminated and saliva- or water-contaminated
substrate surfaces were either left untreated or were cleaned via
phosphoric acid etching or water spray accompanied with or without
adhesive composite application prior applying the adherent PFC material.
SBS was evaluated after thermocycling the specimens (6000 cycles, 5°C
and 55°C). Results: Three-way ANOVA showed that both the surface
contamination and the surface treatment signficantly affected the bond
strength (p < 0.05). Saliva contamination reduced the SBS more than
did the water contamination. SBS loss after saliva contamination was
73.7% and 31.3% for PFC and FRC, respectively. After water
contamination, SBS loss was 17.2% and 13.3% for PFC and FRC,
respectively. The type of surface treatment was significant for PFC (p
Conclusion: Upon
contamination of freshly cured PFC or semi-IPN FRC, surfaces should be
re-prepared via phosphoric acid etching, water cleaning, drying, and
application of adhesive composite in order to recover optimal bond
strength.
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