Aging Protocols and Their Effects on Bond Strength of Total-Etch and Self-Etch Adhesive Systems to Dentin

This study investigated whether different aging protocols have effects on the bond strength of total-etch and self-etch adhesive systems to dentin substrate.

Molars were sectioned exposing the dentin, which was submitted to restorative procedures using two-step total-etch (ASB, Adper SingleBond2), two-step self-etch (CLF, Clearfil SEBond), or one-step self-etch (OPT, Optibond All-in-One) system and resin composite. The obtained blocks were sectioned to result in sticks to be submitted to bond strength and failure mode tests after 24h storage in distilled water (DW), or 180-day aging protocols in DW, artificial saliva (AS), citric acid (CA), or thermal cycling (TC). The types of failures were classified as adhesive, cohesive in dentin, cohesive in composite resin, and mixed. Data were analyzed using ANOVA followed by Tukey’s test (α=5%). The failure modes were descriptive under the relative frequencies form.

It was observed that ASB presented the higher bond strength(p<0.05), while CLF and OPT did not demonstrate differences between them(p>0.05) after 24h. The bond strength obtained with ASB significantly overcame that of OPT when stored in DW or AS for 180 days (p<0.001). In these storing mediums, ASB did not differ from CLF(p>0.05), while in CA or TC the values of CLF were significantly lower (p<0.001). In TC aging, the values presented by OPT did not differ from ASB(p>0.05), both of which had higher values than CLF(p<0.05). The predominant failure mode was adhesive.

For the two-step total-etch and two-step self-etch adhesives, the influence of aging in AS and TC was equivalent to that of storage in DW. The most deleterious effects occurred in CA, a situation in which self-etch adhesives displayed worse performance than the conventional type.