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

ObjectivesStress 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 (Rpmax), stress development (final stress and maximum rate, Rstressmax), degree of conversion (DC) and cross-link density (CLD) of materials containing camphorquinone (CQ), phenylpropanedione (PPD) or CQ/PPD.Materials and methodsRpmax 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).ResultsCQ showed the highest Rpmax and Rstressmax. PPD produced the lowest DC and the highest α  . The mixture CQ/PPD produced statistically lower Rpmax and Rstressmax than CQ alone, but similar DC and CLD.ConclusionCQ/PPD reduced the Rpmax and Rstressmax 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.