Background and Aim: This study aimed to assess the alterations in microhardness of Clearfil Universal Bond Quick (CUBQ), G-Premio Bond (GPB), and Scotchbond Universal (SBU) immediately, 24 hours, and 6 months after curing.
Materials and Methods: In this in vitro study, a composite disc was fabricated. A putty/wash impression was made from the disc to serve as a mold. CUBQ, GPB, and SBU adhesives were applied in the mold, and after allowing 3 hours for the solvent to evaporate, they were cured by a LED curing unit for 20 seconds. Ten specimens were fabricated from each adhesive. The microhardness of the specimens was measured by a microhardness tester immediately, 24 hours, and 6 months after curing. Data were analyzed by repeated measures ANOVA (alpha=0.05).
Results: The mean microhardness of the three adhesives was significantly different immediately after curing (P<0.001), and CUBQ showed significantly higher microhardness than GPB (P<0.001) and SBU (P=0.004). The difference in microhardness of the three adhesives was not significant after 24 hours and 6 months (P>0.05).
Conclusion: The present results showed that the microhardness of all three tested universal adhesives increased with time.