Objective: This research aims to evaluate the properties of ternary methacrylate-thiol-ene composites.
Methods: Mixtures of ethoxylated bisphenol A dimethacrylate (EBPADMA), pentaerythritol tetra(3-mercaptopropionate) (PETMP), and triallyl triazine trione (TATATO) with an inhibitor and a cleavage initiation system are filled with 75 weight percent of glass fillers. Mechanical properties are evaluated by three-point flexural testing with an Instron Materials Testing System. Functional group conversion is determined using Fourier-transform infrared spectroscopy (FTIR) with light curing by a Maxima Pure Power dental light. Volumetric shrinkage is evaluated using a linometer and polymerization stress is measured using a cantilever beam-based tensometer. Temperature profiles are determined using a Fisher Scientific traceable thermometer.
Results: Methacrylate-Thiol-Ene systems achieve nearly 20% higher conversion of methacrylate groups than the control systems. Flexural strength is approximately 50% higher than the controls at equivalent filling ratios and the flexural modulus is 32% higher. Polymerization shrinkage stress is reduced to around 1.4 ± 0.1MPa compared to the controls at an average of 2.5 ± 0.2MPa. The volumetric shrinkage and curing temperature are comparable to the controls.
Conclusion: Methacrylate-thiol-ene systems achieve equivalent or improved volume shrinkage, flexural strength and flexural modulus as compared to the controls and other composite systems. These systems also exhibit increased functional group conversion that will likely improve biocompatibility. Additionally, the dramatic reductions in shrinkage stress may significantly improve longevity and performance making ternary methacrylate-thiol-ene systems attractive alternatives to purely methacrylate based composites.