Method: Three resin cements were selected: Luxacore (LC-DMG Dental), Rely X (RX-3M ESPE) and Variolink (VA-Ivoclar Vivadent) and were activated by two different Light-curing units: Bluephase 16i (16i) and Bluephase 2G (2G - Ivoclar Vivadent) delivering 5, 10 or 20 Joules of total energy. 8 specimens were fabricated from rubber molds. Resin cements were manipulated and inserted in the molds and light activated according to each experimental group. Specimens were taken to a Universal testing machine and submitted to a three-point bending test, at 0.5mm/min. Data were annotated and provided the modulus of elasticity and flexural strength. After testing, data were submitted to statistical analysis. No comparisons were made regarding resin cements. Comparisons were made to evaluate the effects of light-curing units and total energy dose. Therefore, for each resin cement, data were evaluated using Two-way ANOVA and Tukey test, at a level of significance of 5%.
Result: For RX and VA no significant differences were observed when comparing the light-curing units or the total energy dose. For LC, the modulus of elasticity was higher when a 5J dose was applied using 2G; however, Flexural Strength was higher when 16i was used.
Conclusion: The different wavelenghts and energies delivered by the light-curing units might affect the mechanical properties of some resin cements. This, leads to the need of stablishing custom protocols for each resin cement according to the wavelengths of the light-curing units and total energy needed for resin cements activation.