EFFECT OF RADIATION ON RESIN CEMENT MINI-FLEXURAL STRENGTH PROTECTED WITH CERAMIC Y-TZP

Objectives: To evaluate the mini-flexural strength of resin cements submitted to ionizing radiation.
Methods: mini-bars - 12x2x2mm were prepared with RelyX ARC (3M ESPE) and RelyX U200 (3M ESPE) according to the manufacturer's specifications and light-cured through YZ (Vita) and Cercon (DENTSPLY Ceramco). After polymerization, samples were irradiated with 70Gy (Eldorado 78, Atomic Energy of Canadian Limited, ⁶⁰Co gamma radiation) according to the groups (n = 8): UYZγ - RelyX U200 irradiated through YZ; Ucerγ - RelyX U200, irradiated through Cercon, UYZCγ- RelyX U200, irradiated directly; UcerCγ - RelyX U200, irradiated directly; UYZC - RelyX U200, not irradiated; UCerC - RelyX U200, not irradiated; AYZγ - RelyX ARC, irradiated through YZ; Acerγ - RelyX ARC, irradiated through Cercon; AYZCγ - RelyX ARC, irradiated directly; AcerCγ - RelyX ARC, irradiated directly; AYZC - RelyX ARC, not irradiated; ACerC - RelyX ARC, not irradiated. The samples were submitted to mini-3-point bending flexural strength in an universal testing machine (50 kgf cell 5 mm/min). Data were analyzed by 3-way ANOVA and Tukey's test (α=0,05).
Results: ANOVA showed that RelyX ARC has higher flexural strength values when compared to cement RelyX U200 (p<0.0001). For RelyX U200, unprotected irradiation resulted in lower strength values when compared to exposure to radiation through the ceramic (p = 0.002795), while for RelyX ARC there were no significant differences.
Conclusions: We conclude that the type of cement influence mini-flexural strength and exposure to radiation without protection presented under mini- flexural strength for cement RelyX U200.