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Shrinkage strain-rates of dental resin-monomer and composite systems

Paper ID Volume ID Publish Year Pages File Format Full-Text
12070 776 2005 6 PDF Available
Shrinkage strain-rates of dental resin-monomer and composite systems

The purpose of this study was to investigate the shrinkage strain rate of different monomers, which are commonly used in dental composites and the effect of monomer functionality and molecular mass on the rate.Bis-GMA, TEGDMA, UDMA, MMA, HEMA, HPMA and different ratios of Bis-GMA/TEGDMA were mixed with Camphorquinone and Dimethyl aminoethyle methacrylate as initiator system. The shrinkage strain of the samples photopolymerised at Ca. 550 mW/cm2 and 23 °C was measured using the bonded-disk technique of Watts and Cash (Meas. Sci. Technol. 2 (1991) 788–794), and initial shrinkage-strain rates were obtained by numerical differentiation.Shrinkage-strain rates rose rapidly to a maximum, and then fell rapidly upon vitrification. Strain and initial strain rate were dependent upon monomer functionality, molecular mass and viscosity. Strain rates were correlated with Bis-GMA in Bis-GMA/TEGDMA mixtures up to 75–80w/w%, due to the higher molecular mass of Bis-GMA affecting termination reactions, and then decreased due to its higher viscosity affecting propagation reactions. Monofunctional monomers exhibited lower rates. UDMA, a difunctional monomer of medium viscosity, showed the highest shrinkage strain rate (P<0.05P<0.05).Shrinkage strain rate, related to polymerization rate, is an important factor affecting the biomechanics and marginal integrity of composites cured in dental cavities. This study shows how this is related to monomer molecular structure and viscosity. The results are significant for the production, optimization and clinical application of dental composite restoratives.

Dental composites; Monomer system; Shrinkage strain; Shrinkage strain rate; Conversion; Viscosity
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Shrinkage strain-rates of dental resin-monomer and composite systems
Database: Elsevier - ScienceDirect
Journal: Biomaterials - Volume 26, Issue 24, August 2005, Pages 5015–5020
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Physical Sciences and Engineering Chemical Engineering Bioengineering