Effect of a new method to simulate pulpal pressure on bond strength and nanoleakage of dental adhesives to dentin.

Abstract

To evaluate a new method of simulated pulpal pressure in vitro in comparison with the conventional one. Four adhesives were analyzed: a three-step etch-and-rinse (Scotchbond Multi-Purpose [SBMP]), a two-step etch-and-rinse (Single Bond 2 [SB]), a two-step self-etching (Clearfil SE Bond [SE]), and a one-step self-etching (Clearfil S3 [S3]) system. Restorations were built up in flat, deep dentin from extracted molars. After two methods of simulated pulpal pressure or no pulpal pressure (control groups), the samples were cut into sticks and submitted to microtensile bond strength (µTBS) testing and nanoleakage evaluation. Results were analyzed with two-way ANOVA and Tukey's test (p < 0.05). In general, statistical analysis of µTBS showed SBMP>SB=SE>S3. For both methods of simulated pulpal pressure, the µTBS of SB and S3 was lower than in control groups. For SBMP and SE, the µTBS remained stable with simulated pulpal pressure. Conventional and experimental methods of simulating pulpal pressure resulted in similar µTBS (p = 1.00) and nanoleakage patterns. Silver impregnation was higher with SB and S3, especially after simulated pulpal pressure with both methods. The experimental simulated pulpal-pressure method tested here was similar to the conventional method and can be an alternative to it. The simplified adhesives show reduction in bond strength after simulated pulpal pressure. The multistep adhesives have stable bond strengths under simulated pulpal pressure. Therefore, the separate application of hydrophobic resin can achieve resistance to bonding deterioration after hydrostatic pressure.