Efeito do método de medição de contração de polimerização de compósitos convencionais e bulkfill em molares tratados endodonticamente

Abstract

Volumetric shrinkage is an inherent characteristic of resin-based materials, but not all polymerization shrinkage causes shrinkage stresses. So, it is important to distinguish between total shrinkage and the shrinkage that really causes stresses. Therefore, the purpose of this study was to analyze the mechanical properties and the way to calculate the total and post-gel polymerization shrinkage and how it may influence the generation of polymerization shrinkage stress. Methods: Four composite, 2 conventional (Filtek Supreme – FS and TPH3) and 2 bulk fill (FiltekBulkFill Posterior – FBP) were tested for the compression strength test (n = 10) where the samples were made with 6 mm high and 3 mm in diameter and diametraltensilen strength 4mm in diameter and 2mm thick. Assays were performed with a speed of 0.5 mm / min at a universal machine test. The post-gel shrinkage (Shr) was evaluated by the extensometer technique (n = 10) and the total shrinkage (TShr) was measured by optical method (n = 10). The residual shrinkage stress was evaluated by finite element analysis with 4 restorative techniques.Data were analyzed by ANOVA and Tukey's test (α = 0.05).Results:FS (255a) had higher CS than TPH3 (164b), FBP (169b) and SDR (121c). TPH3 (49a) and FS (47ab) had higher DTS than FBP (42bc) and SDR (39c). The highest post-gel and total shrinkage was showed by SDR, 0.45% and 3.93%, respectively. Bulk-filling method accumulated lower residual shrinkage stress than incremental and total shrinkage resulted in higher values than post-gel shrinkage. Conclusion: Shrinkage stress was strongly dependent on the measuring method, type of resin and mechanical properties. Shr seems to be more appropriate to determine the contraction stress generated in restorative protocols.