Alternative photoinitiator system reduces the rate of stress development without compromising the final properties of the dental composite

Abstract

Objectives Stress development during the polymerization process continues to be a major factor that limits predictability and longevity of resin composite restorations. This study evaluated the effect of the photoinitiator type on the maximum rate of polymerization ( R p max ) , stress development (final stress and maximum rate, R stress max ), degree of conversion (DC) and cross-link density (CLD) of materials containing camphorquinone (CQ), phenylpropanedione (PPD) or CQ/PPD. Materials and methods R p max was evaluated via differential scanning calorimetry (DSC). Contraction force measurement was assessed with a single cantilever device for 5 min. The samples were subsequently tested by infrared spectroscopy (FTIR) to evaluate the DC. After, samples were soaked in ethanol to evaluate the swelling coefficient ( α) as a way to estimate the CLD. The results were analyzed by one-way ANOVA and Tukey's test ( p = 0.05). Results CQ showed the highest R p max and R stress max . PPD produced the lowest DC and the highest α. The mixture CQ/PPD produced statistically lower R p max and R stress max than CQ alone, but similar DC and CLD. Conclusion CQ/PPD reduced the R p max and R stress max without a reduction in DC and CLD. Therefore, the use of alternative photoinitiator systems could be a promising way to reduce the stress developed during the composite's polymerization without affecting the final properties.