Effects of Photoinitiator (CQ, PPD) on the Composite Resin

The optimal photo-initiator systems of a light curable dental composite resin depends on many factors such as solubility of photoinitiator compounds in the monomer mixture, absorption characteristics of the initiator, photoreactivity, the effects of these compounds on colour, the light-source and photochemical compatibility, and the biocompatibility of photochemicals. Objectives: The purpose of this study was to evaluate the influence of varying the photoinitiator systems on the physical properties of dental composite resins. Methods: Experimental composite resins were formulated with Bis-GMA, TEGDMA, and 76 wt.% filler particles. The composite resins with 9 combinations (CQ-0.25, CQ-0.50, CQ-0.75, CQ-1.00, PPD-0.50, PPD-1.00, CQ-0.25/PPD-0,75, CQ-0.50/PPD-0.50, CQ-0.75/PPD-0.25) of 2 different photo-initiators (CQ and PPD) were tested. Degree of conversion, surface hardness, and flexural strength were measured to estimate the effect of photoinitiators on the composite resin. Results: The degree of conversion increased with linearly up to 0.75 wt.% of CQ and then showed plateau for further increase of CQ content. PPD was less effective in photo polymerization than CQ. PPD reaction in composite resin is more slow than CQ with compromising the final degree of conversion. In comparing PPD+CQ system to CQ only system, no synergistic effects of PPD on the degree of conversion as well as mechanical properties were observed. Conclusions: The experimental composite resins containing PPD or PPD+CQ did not showed better mechanical properties than that which contained CQ only.