Heat Effect on Viscosity and Curing of Light-Cured Dental Resin and Mechanical Strength of Conventional Dental Composites

Dimethacrylate polymers and silica are most commonly used as matrix resins and fillers for dental composites. Bis-GMA, UDMA are used as base monomers and TEGDMA as a diluent monomer for dental resin preparation. Pure UDMA, mixtures of UDMA:TEGDMA and Bis-GMA:TEGDMA 50:50 and 75:25 were mixed with silanized silica at compositions of monomer:fillers 30:70 and 40:60 (weight ratio). Heat curing of the monomers was studied by DSC and showed that temperature did not have an affect on curing from room temperature to 80°C. The viscosity of the monomers decreased as temperature increased; i.e. by the change of 50°C viscosity reduced to 3-5% of original values at 30°C. There was no significant difference in diametral tensile strength (DTS) of the dental composites having a monomer mixture of 50:50 and 75:25. Stiff monomer (Bis-GMA) shows a higher DTS and Vicker hardness than the flexible one. However, filler content is more prominent in controlling DTS and Vicker hardness than monomer type and ratio. The prepared dental composites showed lower DTS and hardness than the commercial ones.