Effects of Surface-Active Dehydration of Etched Dentin on Bonding to Restorative Resin Material

Residual water in acid-etched dentin is known to interfere with bonding. Butanol-based Surface-Active Displacement Solutions (SADS) were developed in the past for delicate procedures requiring water displacement and surface modification. The aim of this study was to evaluate whether pre-treatment of dentin with SADS containing surfactants of different hydrophilic-lipophilic balance values affected dentin-composite shear bond strength (SBS). Thirty-two extracted healthy bovine incisor teeth were sectioned to obtain 84 samples from the coronal mid-third. These samples were embedded in resin blocks to expose superficial dentin. After acid-etching and water rinsing, samples were randomly divided in 5 groups (n=12) and treated with etch-and-rinse adhesive, or treated with n-butanol/water solution, SADS betaine, SADS L-121 or SADS F-68 for 60 seconds prior to application of adhesive and composite. After incubation in distilled water (24hr, 37.5°C), the bonds were stressed to failure in shear (1 mm/min crosshead speed). One-way ANOVA and Newman--Keuls tests were used for data analysis. Fractured surfaces were examined under a stereomicroscope and scanning electron microscope (SEM) to compare fracture modes. SADS solutions were characterized by contact angle measurements and MAIR-IR spectroscopy. SADS-treated dentin and dentin controls also were characterized by contact angle measurements. Additional samples of the groups showing higher SBS values were prepared and incubated for one month prior to SBS measurements. Based on 24hr mean SBS values (p<0.05), pre-treatment by SADS F-68 (33.91+/-4.15 MPa) and SADS betaine (27.78+/-4.35 MPa) produced significantly higher SBS values, while pretreatment by SADS L-121 (19.55+/-5.84 MPa) and n-butanol solution (16.01+/-4.88 MPa) resulted in significantly lower SBS values relative to the control samples without SADS (22.96+/-4.67 MPa). Similarly for one month analyses, SADS F-68 (26.79+/-2.16 MPa) and SADS-Betaine (24.99+/-1.47 MPa) showed significantly higher SBS values relative to control samples without SADS (19.48+/-3.14 MPa) group. Stereomicroscopic and SEM evaluation revealed mixed/cohesive failure in composite for samples with higher SBS and mixed/adhesive failures for samples with lower SBS. Pre-treatment of etched dentin with SADS containing F-68 or betaine surfactant for 60 seconds improved dentin SBS at both 24 hour and one month after sample preparation. Relevant changes in surface chemistry, that may be acceptable clinically, are under investigation.