Effect of self-curing activators and curing protocols on adhesive properties of universal adhesives bonded to dual-cured composites.

OBJECTIVES: To measure microshear bond strength (μSBS) and nanoleakage (NL) of self-etch universal adhesives under core buildup restorations using different curing protocols, at 24h and after 6-month water storage.

METHODS: Middle dentin of 55 molars was divided into: Clearfil Universal Bond [CFU], Prime&Bond Elect [PBE], and One Coat 7 Universal [OCU]. All-Bond Universal [ABU] and Clearfil SE Bond [CSE] were used as control. CFU, PBE and OCU were: light-cured [LC], dual-cured [DC] and self-cured [SC]. Data were analyzed separately (two-way ANOVA), Tukey's test (α=0.05).

RESULTS: μSBS: At 24h OCU/LC resulted in statistically higher μSBS than ABU. CSE/DC showed statistically higher μSBS than all DC adhesives. PBE/LC resulted in significant lower μSBS than the respective DC/SC modes (p<0.001). At 6-month, both CFU and PBE (LC/SC), resulted in a significant decrease in μSBS. μSBS for OCU/DC decreased significantly (p<0.001) compared to the respective LC/SC modes. NL: At 24h, ABU showed %NL similar to CBU/LC and OCU/LC (p>0.05). CSE/DC resulted in significantly higher %NL than OCU/DC but significantly lower than PBE/DC. CFU/LC/SC resulted in significantly lower %NL than CFU/DC. PBE/SC resulted in significant lower %NL than PBE/LC and PBE/DC. OCU/LC and OCU/DC resulted in significant lower %NL than OCU/SC (p<0.001). At 6-month ABU, CSE, CFU/LC and CFU/SC, resulted in a significant increase in %NL.

SIGNIFICANCE: Self-cured activator and different curing protocols influenced μSBS and NL of self-etch universal adhesives, but this influence was material-dependent.