Shrinkage assessment of low shrinkage composites using micro-computed tomography

Objectives: The aim of this study was to quantify the polymerization volumetric shrinkage of one regular and two low shrinkage bulk fill composites in class I cavities with or without an adhesive layer, using three-dimensional (3D) micro-computed tomography (CT). Methods: Class I cavity preparations (2.5 mm depth x 4 mm length x 4 mm wide) were standardized in 36 extracted human third molars, which were randomly divided in six groups (n=6 each) as follows: Group VIT (regular composite without bonding agent); Group SDR (low shrinkage flowable composite without bonding agent); Group TET (low shrinkage composite without bonding agent); Group VIT/P (regular composite with bonding agent); Group SDR/X (low shrinkage flowable composite with bonding agent); TET/T (low shrinkage composite with bonding agent). Each tooth was scanned via mu CT at cavity preparation, immediately after cavity filling, and after light-curing. Acquired CT data were imported into Amira software for analysis and volume values evaluated between steps from cavity preparation until light-curing. Results: Both low shrinkage composites showed a significantly less volumetric shrinkage than VIT. The use of dental adhesive significantly decreased the average volumetric contraction similarly for the three composites, by about 20%. Conclusion: Both low shrinkage composites showed less volumetric polymerization contraction than the regular composite. The use of dental adhesive decreased the total volumetric shrinkage for all evaluated composites. (c) 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 798-806, 2015.