Effects of repeated use on bond strengths of one-bottle adhesives

Objective: Most one-bottle adhesives contain organic solvents (acetone or ethanol) that displace the water entrapped within the network of collagen fibers in etched dentin. Acetone and ethanol are volatile substances that could easily evaporate from bottles during use. The objective of this in vitro study was to assess the effects of repeated opening of bottles on dentin shear bond strengths of 4 adhesives. Method and materials: Eighty freshly extracted bovine incisors were mounted, polished to 600 grit, and randomly assigned to 8 groups (n = 10). After the application of the materials to 40 specimens at baseline, adhesive use was simulated by opening bottles for 1 minute, 2 times a day, for 3 weeks, except during weekends, when the bottles were kept refrigerated. After 3 weeks of simulated use, the same adhesives were applied to 40 additional specimens. Resin composite was applied to dentin in a No. 5 gelatin capsule and was light-cured. After 500 thermal cycles (5°C to 55°C), shear bond strength testing was performed with a universal testing machine at 0.5 cm/min. Results: Adhesives containing ethanol or water had similar mean bond strengths at baseline and at 3 weeks. The acetone-based material had a significantly lower mean bond strength at 3 weeks than at baseline. Conclusion: Acetone-based adhesives may have a shorter useful life than ethanol- and water-based adhesives.