Hardening of Light-polymerized Resin Cements through Lithium Disilicate Glass-ceramic Veneers

Aim: To evaluate effect of ceramic veneer type and thickness on light attenuation and microhardness of light-polymerized resin cements. Methodology: Three types of ceramic blocks were used (IPS E.max-CAD, Celtra-Duo and VITABLOCS Esthetic-Line). Specimens measuring .5, 1 and 1.5 mm were cut. Deep-cure and Blue-phase light-polymerizations units were used. Light irradiance through specimens was measured with MARC-Patient Simulator. Rely-X Veneer and Variolink-Esthetic resin cements were polymerized through ceramic specimens for 10 and 20 seconds. Microhardness of cement specimens was measured using tester with Knoop indenter. Result: Ceramic type and thickness had statistically-significant effects on light attenuation. Mean microhardness of Rely-X Veneer cement was significantly higher than that of Variolink Esthetic. Moreover, direct correlation was found between polymerization time and mean microhardness for both cements. Conclusions: Increased veneer thickness negatively affected light irradiance in a significant manner. Light attenuation resulted in significant decrease in mean surface microhardness for both cements.M.Sc

Hardness of Resin Cements Polymerized through Glass-Ceramic Veneers

(1) Background: The aim of this study is to evaluate the hardness of resin cements polymerized through ceramic disks under different process factors (ceramic type and thickness, light-polymerization units and polymerization time); (2) Method: Three types of ceramic blocks were used (IPS e.max CAD; Celtra Duo; VITABLOCS). Ceramic disks measuring 0.5 mm, 1.0 mm and 1.5 mm were cut from commercial blocks. Two resin cements (Rely X Veneer and Variolink Esthetic) were polymerized through the ceramic specimens using distinct light-polymerization units (Deep-cure; Blue-phase) and time intervals (10 and 20 s). Hardness of cement specimens was measured using microhardness tester with a Knoop indenter. Data were statistically analyzed using factorial ANOVA (α = 5%); (3) Results: Mean microhardness of Rely X Veneer cement was significantly higher than that of Variolink Esthetic. Deep-cure resulted in higher mean microhardness values compared to Blue-phase at 0.5- and 1-mm specimen thicknesses. Moreover, a direct correlation was found between polymerization time and hardness of resin cement; (4) Conclusions: Surface hardness was affected by resin cement type and ceramic thickness, and not affected by ceramic types, within evaluated conditions. Increasing light-polymerization time significantly increased the hardness of the cement