Durability of resin-dentin bonds: effects of direct/indirect exposure and storage media

To evaluate the longevity of resin-dentin bonds of three adhesives using different storage media and specimen size.

Flat dentin surfaces from extracted human third molars were bonded with: a two-step etch-and-rinse self-priming adhesive (Single Bond), a two-step self-etching adhesive (Clearfil SE Bond), and a one-step self-etching adhesive (One-Up Bond F). Composite build-ups were constructed. The bonded teeth were stored under three conditions: dry, distilled water, or mineral oil. Half of the specimens were stored as intact bonded teeth (Indirect Exposure/IE). The other half were first sectioned into beams and stored under same conditions (Direct Exposure/DE). After storage periods of 24h, 3 months or 1 year, the intact teeth (IE) were sectioned into beams and both subgroups (DE and IE) were tested for microtensile bond strengths. Results were analyzed with multiple ANOVA and Student-Newman-Keuls tests. Fractographic analysis was performed by SEM.

After 24h, Single Bond and Clearfil SE Bond performed equally and were superior to One-Up Bond F. After 3 months of DE to water storage, decreases in bond strengths were observed for Single Bond and One-Up Bond F, this decrease occurred for Clearfil SE Bond after 12 months of water storage. Bonded specimens aged in dry did not alter bond strengths over time. Bond strength increased when Single Bond was stored in mineral oil after 3 and 12 months. Micromorphological alterations were evident after water storage.

Although dentin bond strength of all the adhesives fell over time in DE, SE Bond fells the least.