ABSTRACT
OBJECTIVE: To evaluate properties of silorane-based resins and composites containing a stress reducing monomer. METHODS: Resin mixtures and composites were formulated containing (a) a developmental stress reducing monomer [TOSU; Midwest Research Institute]; (b) Sil-Mix (3M-ESPE); (c) photo cationic initiator system. Standard BISGMA/TEGDMA resin (B/T) and composite (Filtek Z250) were used as controls. Polymerization volume change was measured using a NIST mercury dilatometer and polymerization stress using an Enduratec mechanical testing machine. Three point bend tests determined flexural elastic modulus, work of fracture, and ultimate strength (ADA 27; ISO 4049). Fracture toughness was measured using ASTM E399-90. Four groups of resins and composites were tested: Sil-Mix, methacrylate standard, and Sil-Mix with two addition levels of TOSU. An ANOVA was used and significant differences ranked using Student-Newman-Keuls test (alpha=0.05). RESULTS: Polymerization stress values for resins containing TOSU were significantly less than the other materials. Polymerization shrinkage values for Sil-Mix formulations were significantly less than for B/T, but were not different from each other. TOSU-containing formulations generally had somewhat lower mechanical properties values than Sil-Mix or B/T. Polymerization stress values for Sil-Mix-based composites were significantly less as compared to Z250. The 1wt.% TOSU composite had the lowest stress. No difference between composite groups was noted for fracture toughness or work of fracture. For ultimate strength, the 5wt.% TOSU formulation differed significantly from Z250. All Sil-Mix formulations had elastic modulus values significantly different from Z250. SIGNIFICANCE: The ability of TOSU to reduce polymerization stress without a proportional reduction in mechanical properties provides a basis for improvement of silorane-based composites.
Subject(s)
Composite Resins/chemistry , Silicon Compounds/chemistry , Spiro Compounds/chemistry , Trimethylsilyl Compounds , Alkanes/chemistry , Analysis of Variance , Composite Resins/chemical synthesis , Composite Resins/radiation effects , Dental Marginal Adaptation , Dental Stress Analysis , Elasticity , Epoxy Compounds/chemistry , Hardness , Light , Materials Testing , Phase Transition , PliabilityABSTRACT
Polymerization volume change (PVC) was measured systematically using mercury dilatometry for 41 epoxide and methacrylate monomers with quartz filler. Quantitative structure property relationship (QSPR) models were developed based on this previously unreported data to gain insight in the data collection method for future models. Successful models included only data from those samples which polymerized to hardness. The most significant descriptors in these models related to monomer reactivity. In contrast, PVC data collected under experimental conditions which maximized monomer conversion resulted in descriptors describing size and branching, indicating conversion must be considered for future PVC measurements. A Rule of Mixtures (ROM) correction term improved correlations of the dilatometer data with varying quartz content, and an adjustment for conversion may similarly enable inclusion of data which had not polymerize to hardness.
