Effect of LED light-curing on the relative hardness of tooth-colored restorative materials

Abstract

Objective: To determine the relative hardness of Gl-based restorative materials using both LED and QTH curing lights at different post-irradiation intervals. Methods: Four restorative materials (Z250, Beautifil, Dyract AP and Fuji II LC) with shade A3.5 were tested in conjunction with three LCUs (Astralis 3, Blue phase and Radii). The specimens were prepared using specially constructed molds, irradiating only the top surface to an equivalent energy density (J/CM). Vickers microhardness measurements were performed for both the top and bottom surfaces of all specimens following dry storage for 15 minutes in the dark. The measurements were repeated after 24 hours and 7 days. Mean VHNs and SD of the top and bottom surfaces of each specimen were calculated. Relative hardness values (RH) were also determined and mean RH was calculated for each group. Results: The top surface of the Z250, Beautifil and Dyract materials were significantly harder than the bottom surface (p<0.05) with all LCUs and at all time intervals. Conversely, a different trend was observed with Fuji II LC, where bottom surface VHNs were significantly higher than top surface values (p<0.05). Blue phase was the only LCU that recorded RH values above 80% for all tested material at all post-irradiation intervals. Conclusions: A highintensity LED LCU used for 10 seconds resulted in RH values greater than 80%, with all four restoratives tested indicating a sufficient degree of monomer conversion with such a short curing cycle.