Properties of a new dental photocurable resin based on the expanding monomer and three-component photoinitiator system

The purpose of this study was to use a three-component photoinitiation system comprising 1wt% CQ (camphorquinone), 2wt% DMAEMA (2-(dimethylamino) ethyl meth acrylate) and 2wt% (PhI+PF6)-I-2 (-) (diphenyliodonium hexafluorophosphate) to initiate the copolymerization of the matrix resins which combine bisphenol-S-bis (3-methacrylate-2-hydroxy propyl) ether (BisS-GMA) with the expanding monomer unsaturated spiro orthoesters 2-methylene-1,4,6-trispiro[4,4] nonane (MTOSN), for minimizing the volumetric shrinkage that generally occurs during polymerization. It was hypothesized that MTOSN would expand volumetrically during polymerization under the three-component photoinitiator system and further reductions in volumetric shrinkage would be obtained. The performance study which consists of degree of conversion and condition of the ring-opening reactions of MTOSN, volumetric shrinkage and mechanical properties including tensile bond strength, compressive strength and Vicker's hardness were carried out respectively by Fourier transfer infrared, the dilatometer and the universal testing machine. The results supported that the dental composites based on the expanding monomer and three-component photoinitiator system engendered a greater decrease of volumetric shrinkage and better mechanical properties.