Effect of Etching Mode on the Dentin Bond Durability of Universal Adhesives

This study evaluated the effects of etching mode, pH, and composition on the shear bond strength of three universal adhesives (UAs), in comparison with conventional adhesives.

Crowns from 110 extracted third molars were sectioned to obtain 220 dentin surfaces and allocated into 11 groups (n = 20) based on adhesive system (OptiBondFL, ClearfilSE Bond, All-Bond Universal, OptiBond Universal, G2-Bond Universal) and etching mode (etch-and-rinse [ER], self-etch [SE], selective dentin etching [SDE]). Each group was divided into pre- and post-aging sub-groups. Shear bond strength was tested at 24h and after 5,000 thermal cycles. The resin-dentin interface was examined using scanning electron microscopy (SEM). Data were analyzed using one-way ANOVA, LSD post-hoc and paired-sample t-tests (α = 0.05).

All-Bond Universal exhibited the highest bond strength across all modes, while OptiBond Universal showed the lowest. No significant difference was observed between ER and SE modes for most UAs, except G2-Bond Universal. SDE did not result in significantly higher bond strength compared to SE or ER in any group. After aging, G2-Bond Universal in SE mode exhibited the highest bond strength.

Bond strength was influenced by etching mode, pH, and composition of the adhesive. UAs performed comparably to the gold-standard SE adhesive in SE mode; however, their performance in ER mode varied depending on their composition and pH.

To ensure predictable clinical outcomes, clinicians should recognize that UAs do not perform uniformly. Selecting both the adhesive and etching mode according to the adhesive's composition may enhance long-term bonding success.