Cut Enamel Prism Orientation Affects the Self-Etched Bond Interface

Effective enamel bonding is critical to dentistry. New self-etching adhesive systems (SE) are questionable on their ability to adequately etch enamel. Differences exist in the bond produced by SE to cut and uncut enamel. More recently, it has been suggested that orientation of the cut surface to enamel prisms may affect the nature of the bond produced by SE. Objective: to compare bonding effectiveness to parallel and cross-cut enamel prisms by SE and total-etching systems (TE) as measured by microleakage in vitro. Methods: Standard triangular preparations were cut into the buccal and lingual enamel of 30 extracted human molars such that each cavity had parallel and cross-cut prisms exposed at the cavo-surface margin. Paired preps on each molar were subjected to either SE-bonding (Adper Prompt, 3M ESPE) or TE-bonding (Phosphoric acid/ Adper Single Bond, 3M ESPE) followed by restoration with Filtek Supreme (3M ESPE). Teeth were subjected to cyclic fatigue (25,000x, 5-30N) and thermocycling (500x, 5-55C). Silver nitrate staining was used as the leakage marker, and measurements were made on tooth sections under a microscope (30x) with image analysis software. Results: Linear mixed effects model analyses show that, overall, microleakage of cross-cut is lower than that of parallel-cut samples and that the lowest leakage detected was from SE on cross-cut enamel (p<0.001). Means+SD (mm microleakage) are: TE; Parallel = 0.51+0.35,Cross-cut =0.54+0.36 and SE; Parallel = 0.59+0.31, Cross-cut = 0.29+0.24. Conclusions: 1) self etching adhesive Adper Prompt is equally effective in bonding to cut enamel of any orientation than a total-etching adhesive system, and 2) the least microleakage is produced by the self etching system on cross-cut enamel prisms.