Effect of Phenyl-P/HEMA acetone primer on wet bonding to EDTA-conditioned dentin

Objectives: The purpose of this study was to examine the effect of 2-methacryloyloxyethyl phenyl phosphoric acid (Phenyl-P)/2-hydroxyethyl methacrylate (HEMA) acetone-based primer on moist dentin surfaces that were preconditioned with ethylenediaminetetraacetate (EDTA) to remove the smear layer. Methods: Bovine dentin were prepared with 180-grit paper, conditioned with 0.5 M EDTA (pH 7.4) for 60 s followed by water rinsing and then blot drying. Each surface was then primed with Phenyl-P/30 wt% HEMA in acetone for 10 s followed by blot drying. A light-cured bonding agent was then applied, cured and trimmed to give dumbbell-shaped specimens. The Phenyl-P concentration ranged from 1 to 20 wt%. During the bonding procedure, no compressed air was used. After storage in water at 37°C for one day, tensile bond strengths were measured and analyzed using one-way ANOVA. Dentin discs treated under the same conditions were observed under a scanning electron microscope (SEM). Results: When the concentration of Phenyl-P was 12 wt%, the highest mean tensile bond strength was obtained (27 MPa). It was significantly higher than that of the 3, 5, 15 or 20 wt% groups (9–11 MPa) (p<0.05). The samples of 1 wt% group were all broken during trimming the dumbbell-shaped specimens. SEM observations showed a 1 μm-thick layer of hybridized dentin after polished cross-sections were chemically challenged with 6 N HCl for 30 s and then 1% NaOCl for 60 min. Significance: The experimental Phenyl-P/HEMA acetone primer is effective in bonding resin to EDTA-conditioned dentin. Acetone as a solvent for Phenyl-P/HEMA primer has the clinical advantage of not requiring an air-stream to evaporate the solvent. The experimental bonding procedure can minimize the skin irritation by HEMA.