• Pimmada Kesrak D.D.S.
• Chalermpol Leevailoj D.D.S., M.S.D., ABOD, FRCDT

Objective The present study aimed to evaluate the surface hardness of two light-cured resin cements
polymerized under different ceramic discs.

Materials and methods Ceramic discs (10 mm in diameter and 0.5, 1.0, 1.5 and 2.0 mm thick) were
prepared from IPS e.max^® Press high translucency (HT), IPS e.max^® Press high opacity (HO) (Ivoclar
Vivadent, Liechtenstein) and Cercon^® (DeguDent, Germany). The light-cured resin cement specimens
were prepared from Variolink^® Veneer (high value +3) (Ivoclar Vivadent, Liechtenstein) and NX3
Nexus^® Third Generation (white opaque) (Kerr Corporation, USA). The control groups (2 groups)
were 2 types of resin cement which were directly activated by the LED light curing unit and the
experimental groups (24 groups) were 2 types of resin cement light activated through 3 different
ceramics of 4 thicknesses each as described above. After light activation, the specimens were stored in
an incubator at 37°C for 24 hours. Knoop hardness measurements were obtained with 50 grams-force
for 15 seconds. Three indentations were made for each specimen and the mean surface hardness was
calculated for each specimen. The data were analyzed statistically using three-way ANOVA, t-test
and two-way ANOVA

Results The surface hardness of the resin cements polymerized under different ceramic discs was
significantly different from the hardness of control group (p < 0.05). The surface hardness of NX3 was
significantly higher than that of Variolink^® Veneer (p < 0.05) in all experiment groups.

Conclusion The surface hardness of resin cement polymerized under different ceramic types and
thicknesses was significantly different. Increasing in ceramic thickness decreased the surface hardness
of resin cement.

(CU Dent J. 2011;34:87-98)