Light- and time-dependent polymerization of dual-cured resin luting agent beneath ceramic

Objective. In this study we investigated the degree of conversion (DC) of a dual-cured resin luting agent beneath a ceramic of different thickness. Material and Methods. The luting material (RelyX) was photo-activated for 40 s through ceramic disks (Empress Esthetic, 0.7, 1.4, or 2 mm thick). Dual (DUC) and chemically cured (CC) control groups were obtained. A delayed exposure (DE) procedure was tested in which the material was light-activated after 5 min without using ceramic. DC (%) was measured using infrared spectroscopy at 40 s, 1, 2, 4, 6, 8, and 10 min. Light irradiance and spectrum transmitted through ceramic were measured using a power meter and a spectrometer. Results. A decrease in irradiance was detected with increasing ceramic thickness, but no alteration in the emission profile was observed. At 10 min, all groups showed DC higher than at 40 s. No significant differences were detected for DUC compared with the groups indirectly activated through the ceramic disks. Generally, CC showed the lowest DC values. No significant effect in DC was detected for DE after 10 min. A significant increase in DC was generally detected only up to 4 min. Conclusions. The luting agent was dependent on light exposure and time to obtain improved DC. Neither the indirect activation nor the DE procedure significantly influenced the final DC.