Thiol-ene-methacrylate composites as dental restorative materials.

OBJECTIVES: The objective of this study was to evaluate composite methacrylate-thiol-ene formulations with varying thiol:ene stoichiometry relative to composite dimethacrylate control formulations. It was hypothesized that the methacrylate-thiol-ene systems would exhibit superior properties relative to the dimethacrylate control resins and that excess thiol relative to ene would further enhance shrinkage and conversion associated properties. METHODS: Polymerization kinetics and functional group conversions were determined by Fourier transform infrared spectroscopy (FTIR). Volume shrinkage was measured with a linometer and shrinkage stress was measured with a tensometer. Flexural modulus and strength, depth of cure, water sorption and solubility tests were all performed according to ISO 4049. RESULTS: All of the methacrylate-thiol-ene systems exhibited improvements in methacrylate conversion, flexural strength, shrinkage stress, depth of cure, and water solubility, while maintaining equivalent flexural modulus and water sorption relative to the dimethacrylate control systems. Increasing the thiol to ene stoichiometry resulted in further increased methacrylate functional group conversion and decreased volume shrinkage. Flexural modulus and strength, shrinkage stress, depth of cure, water sorption and solubility did not exhibit statistically significant changes with excess thiol. SIGNIFICANCE: Due to their improved overall functional group conversion and reduced water sorption, the methacrylate-thiol-ene formulations are expected to exhibit improved biocompatibility relative to the dimethacrylate control systems. Improvements in flexural strength and reduced shrinkage stress may be expected to result in composite restorations with superior longevity and performance.

Characterization of N'Durance: a nanohybrid composite based on new nano-dimer technology.

High molecular weight dimethacrylate systems within composite resins present a number of clinical deficiencies, including insufficient monomer conversion, polymerization shrinkage, and polymerization stresses. This study aimed to determine physical and chemical properties of a new high monomer conversion nanohybrid composite resin based on nano-dimer technology (N'Durance), compared to other principal products on the market. Specimens were polymerized using a visible light lamp following the manufacturers' instructions. Compressive and flexural strengths, flexural modulus, water sorption, and tensile strength were determined. Water absorption and solubility were measured. Monomer conversion, polymerization shrinkage, and polymerization stress were calculated. It was shown that products using conventional resin (Bis-GMA/TEGDMA) have an average conversion of 60% for the microhybrids and 50% for the nanofilled composites. The shrinkage stress and contraction with N'Durance are lower than most commercial products: shrinkage contraction was reduced from 2.3% (average of the regular composite) to 1.5%, and the shrinkage stress from 2.5% to 1.1%, with an increase of approximately 27% in the monomer conversion. For products that use conventional resin, volumetric shrinkage increases when the final double bond conversion is increased to reduce the unreacted monomers; however, N'Durance shows high conversion and low polymerization shrinkage.