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The organic phase of resin composites is constituted by dimethacrylate resins, the most common monomers being the bisphenol A diglycidildimethacrylate (BisGMA), its ethoxylated version (BisEMA), triethylene glycol dimethacrylate (TEGDMA) and urethane dimethacrylate (UDMA). This study compared the homopolymers formed from the monomers used in restorative(More)
Optical properties of composite restoratives, both cured and uncured, are of obvious importance in a procedure reliant on photoactivation, since they may affect light transmission and therefore materials conversion upon which mechanical properties and ultimate clinical performance are dependent. The objective of the present study was to evaluate(More)
Different monomer structures lead to different physical and mechanical properties for both the monomers and the polymers. The objective of this study was to determine the influence of the bisphenylglycidyl dimethacrylate (BisGMA) concentration (33, 50 or 66 mol%) and the co-monomer content [triethylene glycol dimethacrylate (TEGDMA), ethoxylated bisphenol-A(More)
OBJECTIVES Verify the influence of curing methods on contraction stress, stress rate, and degree of conversion (DC) of a restorative composite and on bond strength of composite restoratives. METHODS For the stress test, composite (0.84 mm thick) was applied between two 5-mm diameter glass rods, mounted in a servohydraulic machine. Stress rate was taken by(More)
OBJECTIVES Evaluate the influence of pulse-delay curing on shrinkage stress and microhardness of 2 restorative composites (Herculite XRV and Tetric Ceram). METHODS Two pulse irradiances (500 and 100 mW/cm2) were applied for 1 or 5 seconds, respectively (radiant exposure = 0.5 J/cm2). In both cases, photoactivation was completed applying 500 mW/cm2 for 39(More)
OBJECTIVES Evaluate the effect of testing system compliance on polymerization stress and stress distribution of composites. METHODS Composites tested were Filtek Z250 (FZ), Herculite (HL), Tetric Ceram (TC), Helio Fill-AP (HF) and Heliomolar (HM). Stress was determined in 1-mm thick specimens, inserted between two rods of either poly(methyl methacrylate),(More)
The definition of an optimal elastic modulus for a post is controversial. This work hypothesized that the influence of the posts' elastic modulus on dentin stress concentration is dependent on the load direction. The objective was to evaluate, using finite element analysis, the maximum principal stress (sigma(max)) on the root, using posts with different(More)
PURPOSE To evaluate the effect of light guide distance and the different photoactivation methods on the degree of conversion (DC) and microleakage of a composite. METHODS AND MATERIALS Three photoactivation protocols (600 mW/cm2 x 40 seconds; 400 mW/cm2 x 60 seconds or 200 mW/cm2 x 20 seconds, followed by 500 mW/cm2 x 40 seconds) and three distances from(More)
Polymerization stress development results from the complex interplay of volumetric shrinkage, reaction kinetics, and viscoelastic properties. The objective of this study was to examine the relationships among volumetric shrinkage, degree of conversion, rate of polymerization (RP(max)), and stress development for 2 model bis-GMA-based composites. Three(More)
The resin phase of dental composites is mainly composed of combinations of dimethacrylate comonomers, with final polymeric network structure defined by monomer type/reactivity and degree of conversion. This fundamental study evaluates how increasing concentrations of the flexible triethylene glycol dimethacrylate (TEGDMA) influences void formation in(More)