Effect of long-term storage temperatures on the bond strength of self-etch adhesives

Manufacturers often recommend refrigerated storage of self-etching enamel and dentin adhesives. The purpose of this study was to compare the shear-bond strength of composite resin to dentin using two different self-etching adhesives after extended storage at room or refrigerated temperatures. One- and two-step self-etching bonding agents were stored separately at room (23 degrees C) or refrigerated temperatures (5 degrees C) per manufacturer recommendations for 1, 4, or 18 months before testing. After each time period, composite resin was bonded to the dentinal surface of extracted human third molars using a mold and tested in shear on a universal-testing machine. Data were analyzed with analysis of variance/Tukey's test. No significant difference in bond strengths was found on the basis of storage temperature for either adhesive type. The one-step adhesive had a significant loss in bond strength over the 18 months of storage. However, the two-step self-etch adhesive had no loss in bond strength, regardless of storage temperature.