Effects of Photoinitiator on the Esthetic Properties of Composite Resin

The optimal photo-initiator system of a light curable dental composite resin depends on many factors such as solubility of photo-initiator 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 photo-initiator systems on the esthetic properties of dental composite resins. Methods: Resin matrix was prepared with resin mixtures containing 70 wt.% Bis-GMA and 30 wt.% TEGDMA and 9 combinations (CQ-0.25wt.%, 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). Experimental composites were made with resin matrix added to a total of 76 wt.% inorganic fillers, which were loaded with Ba-glass minifiller (1 µ) 70 wt.%, pyrogenic silica microfiller (0.04 µ) 3 wt.%, and silica nanofiller (7 µ¬) 3 wt.%. Opacity, color stability, and CIE color coordinates were measured to estimate the effect of photoinitiators on the esthetic properties of composite resin. Results: The discoloration of specimens decreased with increasing of CQ fraction. The experimental composite resins with containing PPD or PPD+CQ did not show better optical properties than those with that which contained CQ only. As irradiation times were extended to 120 sec, the specimens with PPD showed the higher opacity, b* value, and color change than the specimens with CQ only. Conclusions: Replacement of CQ photoinitiator to PPD did not enhance the esthetic properties of composite resins. Addition of PPD to composite resins may delay the photopolymerization reaction then cause less color stable than composite resin with CQ only.