Laboratory Comparison of Polymerization Rate of P60 Resin Composite during Different Curing Time by Two Light Curing Units: An in vitro Study

Performance of resin composites depend on their polymerization rate. Minimum curing time to achieve desired polymerization rate is 40 seconds. P60 resin composite manufacturer has claimed reduced curing time as one of the advantages of this resin composite. Since increasing the lifetime of light curing unit and reducing the treatment period is important in pediatric dentistry، however the aim of this study was to compare the polymerization rate of P60 resin composite with 20 and 40 seconds intervals by Halogen and LED curing units. In this in vitro study، 40 disks from resin composite were provided with 5-mm diameter and 2-mm thickness. The samples were randomly divided into four groups each containing ten disks. The specimens of the first and second groups were cured for 20 and 40 seconds by Halogen units، respectively. Also، the third and fourth groups were cured by LED for 20 and 40 seconds، respectively. Polymerization rate was evaluated by spectroscopy device. Data were analyzed using two way ANOVA (α=0. 05). Two-way ANOVA test showed that regardless of the type of device، the polymerization rate was significantly higher at 40 seconds compared to 20 seconds. Also، the polymerization rate by Halogen units was meaningfully higher than the LED units. Nevertheless، in both units، the rate of polymerization was acceptable at 20 seconds duration. Considering the limitations of a laboratory study، it seems that regardless of the type of light curing unit، 20 seconds is enough to cure P60 resin composite.