Color stability, conversion, water sorption and solubility of dental composites formulated with different photoinitiator systems

Objectives: The aim of this study was to formulate materials with high color stability and reduced degradation by using photoinitiator systems derived from phosphine oxides alternative to the traditional camphorquinone (CQ)/amine system. Methods: Materials were formulated with the monomers BisGMA and TEGDMA as organic matrix. The photoinitiators tested were CQ+ amine (EDMAB), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO), BAPO + EDMAB, diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide (TPO) and TPO + EDMAB. A 60% mass of silanated glass filler particles was added. Degree of C=C conversion was evaluated by Fourier -transformed infrared spectroscopy 10 min after photopolymerization. The color properties were evaluated by a digital spectrophotometer, applying the CIELab parameters, either before photoactivation, immediately after photoactivation, 24 h after dry storage, and one month after water immersion. Water sorption and solubility were assessed by mass gain or loss after storage in water for 30 days. Data were analyzed using ANOVA and Tukey's test (5%). Results: Degree of conversion did not differ statistically among all the tested formulations. Regarding color, only groups with TPO presented satisfactory color stability after one month of water storage (AE < 3.3). Water sorption and water stability did not differ among the groups. Conclusions: Degree of conversion, water sorption and water solubility did not differ among all the tested groups. The TPO-based groups were the only materials with satisfactory color stability after one month of water storage. Clinical significance: The use of a photoinitiator system containing TPO might improve the color stability of resin composites compared with the traditional CQ/amine system while attaining similar physico-chemical properties for the composite. CD 2012 Elsevier Ltd. All rights reserved.