Effect of Different Light Curing Modes, Composites and Storage Times

Objective: Determine the effect of different curing units and storage times on the flexural strength of different dental composite specimens. Material and Methods: Packable composite (PC)(surfill^tm ,Dentsply), nanohybrid composite (NC)(Tetricevoceram^tm, Ivoclar, Vivadent) and microhybrid low shrinkage composite (MC)(Inten-s^tm Ivoclar ,Vivadent ) specimens were produced at the dimensions 25 x 2 x 2 mm, (ISO 4049 ). The three different curing methods involved a conventional halogen unit (Optilux 401^tm Demetron), a halogen unit on ramping mode (Optilux 501^tm, Demetron) and LED curing unit (LE Demetron ^tm, Demetron). Specimens (N = 6/group) were stored in filtered DI water at 37^oC for 30 mins; 2 hours; or 5 days. Three point bend test determined the ultimate flexural strength. Data was analyzed in a 3x3way ANOVA, followed by Fisher's PLSD. Results: Table shows the mean flexural strengths in MPa for tested samples (N=6 for all groups): Fisher's PLSD intervals (p<0.0001) for comparison of means between curing lights, composites and storage times were 3.6 for all variables. There were significant differences between LED to QTH and Ramp for all composites and storage time groups except MC, 2 hrs, Ramped was significantly higher than the other 2 lights. Conclusions: LED curing mode exhibited a significant difference on all composites except MC at 2 h. Packable composite gave the highest flexural strength under all curing conditions, and polymerization increased flexural strength over time.This work was supported by a fellowship (HD) from the Egyptian Embassy Washington DC, and materials were kindly provided by Dentsply Inc.and Vivadent