Thiol-ene-methacrylate composites as dental restorative materials

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.

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.

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.

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.