Microtensile bond strength of universal adhesives to flat versus Class I cavity dentin with pulpal pressure simulation

Abstract

Objectives: The aim of this study was to test long-term microtensile bond strength (mu TBS) of 2 universal adhesives applied to dentin following "total-etch" (TE) or "self-etch" (SE) protocols and aged by direct or indirect water exposure using simulated pulpal pressure. Materials and methods: Single Bond Universal (SBU, 3M ESPE) or Ipera Bond (IP, Itena) were applied to mid-coronal dentin ("flat dentin") or Class I cavity ("cavity dentin") following TE or SE protocols in 112 extracted human third molars. Sixteen groups (n=7 per group) were prepared, 8 groups for mu TBS measurements after 24 hours, and further 8 groups for measurements after 6 months storage. "Cavity dentin" groups were subjected to simulated hydrostatic pulpal pressure of 15 cm H2O using a custom-made device before cutting 1 x 1 mm sticks while "flat dentin" groups were cut into sticks and directly exposed to deionized water. Results: Generally, the TE protocol resulted in highest mu TBS values on flat dentin initially for both adhesives (general linear model, P lt .05). Long-term storage resulted in significantly lower mu TBS values for the TE protocol (P lt .05) while the SE protocol showed comparable values after 6 months (P>.05). "Cavity dentin" with simulated pulpal pressure resulted in lower mu TBS than "flat dentin" (P lt .05). For both adhesives, mu TBS was in the range of 19-42 MPa initially and 16-36 MPa after 6 months storage. Conclusions: mu TBS to dentin of universal adhesives is more stable in the long term following the SE than TE protocol. Simulated pulpal pressure and cavity-type sample preparation may be recommended for mu TBS testing as a more clinically relevant strategy.