Abstract
ObjectiveThe aim of this in vitro study was to evaluate the microtensile bond strength (µTBS) to dentin of two different restorative systems: silorane-based (P90), and methacrylate-based (P60), using two cavity models.Material and MethodsOcclusal enamel of 40 human third molars was removed to expose flat dentin surface. Class I cavities with 4 mm mesial-distal width, 3 mm buccal-lingual width and 3 mm depth (C-factor=4.5) were prepared in 20 teeth, which were divided into two groups (n=10) restored with P60 and P90, bulk-filled after dentin treatment according to manufacturer's instructions. Flat buccal dentin surfaces were prepared in the 20 remaining teeth (C-factor=0.2) and restored with resin blocks measuring 4x3x3 mm using the two restorative systems (n=10). The teeth were sectioned into samples with area between 0.85 and 1.25 mm2 that were submitted to µTBS testing, using a universal testing machine (EMIC) at speed of 0.5 mm/min. Fractured specimens were analyzed under stereomicroscope and categorized according to fracture pattern. Data were analyzed using ANOVA and Tukey Kramer tests.ResultsFor flat surfaces, P60 obtained higher bond strength values compared with P90. However, for Class I cavities, P60 showed significant reduction in bond strength (p<0.05). No statistical difference between restorative systems was shown for Class I cavity model (p>0.05), or between Class I Cavity and Flat Surface group, considering P90 restorative system (p>0.05). Regarding fracture pattern, there was no statistical difference among groups (p=0.0713) and 56.3% of the fractures were adhesive.ConclusionIt was concluded that methacrylate-based composite µTBS was influenced by cavity models, and the use of silorane-based composite led to similar bond strength values compared to the methacrylate-based composite in cavities with high C-factor.
Highlights
The majority of composites used in restorative dentistry are chemically based on the polymerization reaction of methacrylates
After application of Tukey’s test, it was observed that, for the Flat Surface cavity model, P60 restorative system showed higher bond strength compared with P90 (p
The bond strength values for P60 restorative system in Class I cavity model was statistically lower when compared with the Flat Surface cavity model (p
Summary
The majority of composites used in restorative dentistry are chemically based on the polymerization reaction of methacrylates This reaction presupposes the conversion of monomer molecules into a polymeric network, within which van der Waals spaces are replaced by covalent bonds that approximate the molecules and cause considerable contraction of the composite. Polymerization shrinkage is an intrinsic property of the resin matrix, which has been undesirably ascribed to problems associated with failures in posterior teeth resin composite restorations. These failures may be cohesive fracture of enamel prisms and microgap formation, with rupture of adhesive bonds and consequent withdrawal of the restorative material from the cavity walls. Marginal microleakage, marginal staining, postoperative sensitivity and secondary caries can be expected.
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