Polymerization Kinetics of Conventional vs. Fiber-Reinforced Composites Using Rapid High-Intensity Photo-Activation

This in vitro study examined the effects of rapid high-intensity vs. conventional light-curing on real-time degree of conversion (DC) of conventional and fiber-reinforced resin composites. Two resin composites specifically designed for rapid high-intensity photo-polymerization (Tetric PowerFill, Tetric PowerFlow), two flowable fiber-reinforced composites (everX Flow, FibraFill Flow), and two condensable fiber-reinforced composites (everX Posterior, FibraFill DENTIN) were included. Photo-activation was performed using two protocols: 3 s at 3006 mW/cm2 or 10 s at 1108 mW/cm2. DC of 1.5 mm thick specimens (n = 6) was monitored for 5 min by real-time ATR-FTIR spectroscopy, and the maximum polymerization rate (RDCmax) was determined. Data were analyzed using independent t-tests and ANOVA followed by Tukey’s post hoc test (α = 0.05). DC at the end of the 5 min observation period ranged from 33.7 ± 0.9% (FibraFill DENTIN, 3 s) to 59.2 ± 0.3% (Tetric PowerFlow, 10 s). All composites exhibited a significantly higher DC with the 10 s curing protocol compared with 3 s high-intensity light-curing. Within both curing protocols, Tetric PowerFlow, everX Flow, and everX Posterior achieved the highest DC values, whereas FibraFill DENTIN showed the significantly lowest DC. RDCmax was significantly higher with the 3 s protocol than with 10 s light-curing for all materials, with the significantly highest values recorded for Tetric PowerFill and Tetric PowerFlow. FibraFill DENTIN and FibraFill Flow exhibited the significantly lowest RDCmax for both curing protocols. In conclusion, 3 s high-intensity photo-activation increased the polymerization rate but simultaneously reduced the degree of conversion of conventional and fiber-reinforced flowable and condensable resin composites compared with a conventional 10 s light-curing regimen.