The purpose of this study was to compare shear bond strengths of self-adhesive resin cements on dry or moist dentin. Eighty non-carious, extracted human molars were cut horizontally to dentinal surfaces. Four self-adhesive resin cements: RelyX U100® (RU1), RelyX U200® (RU2), Maxcem elite® (MC), Clearfil SA luting® (CL) were used as luting agent in each group (N = 10). Therefore, the experimental groups were 1) RU1 + Dry, 2) RU1 + Moist, 3) RU2 + Dry, 4) RU2 + Moist, 5) MC + Dry, 6) MC + Moist, 7) CL + Dry, 8) CL + Moist. A single side masking tape with 2 mm diameter hole was applied to the centre of dentin surface. The resin composite rod was luted to prepared dentin surface
in each group with the applying load of 1,000 grams, then light cured for 40 second for each side.The bonded specimens were then stored in distilled water at 37 oC for 24 ​hours. Shear bond strength was evaluated using universal testing machine at cross head speed of 0.5 mm/min. The data were collected and statically analyzed using two-way analysis of variance and Tukey’s multiple comparisons at 95 % confidence level. For the same product, the mean shear bond strengths of self-adhesive resin cement luted on dry or moist dentin were not significantly different. Among 4 self-adhesive resin cements, shear bond strengths of RelyX U100® [dry 9.42 (1.32), moist 9.06 (1.21)], RelyX U200®
[dry 9.30 (1.29), moist 9.27 (0.98)] and Maxcem elite® [dry 9.14 (1.23), moist 8.23 (1.61)] were not significantly different but they were significantly higher than Clearfil SA luting® [dry 4.32 (1.44), moist 4.84 (1.76)] in both dentin conditions (p < 0.05). All specimens showed adhesive failure at cement-tooth interface. In conclusion, there was no significant difference in shear bond strength of self-adhesive resin cements to dry or moist dentin. Shear bond strengths of RelyX U100®, RelyX U200® and Maxcem elite® were not significantly different but they were significantly higher than Clearfil SA luting® in both dentin conditions.