Use of a bonding agent to reduce sealant sensitivity to moisture contamination: an in vitro study

Moisture contamination of etched enamel during application of sealant is the most frequently cited reason for sealant failure. In preliminary studies, a dentin bonding agent (Scotchbond Dual Cure, 3M, St. Paul, MN) has been shown to bond adequately to etched enamel after salivary contamination. This study investigated bond strength in vitro, when a bonding agent was used beneath sealants under varied conditions of contamination. Five hundred bovine incisor crowns were separated randomly into eight groups. The enamel samples, etched for 60 sec with a 37% phosphoric acid gel, were contaminated with: 1) fresh whole saliva, air dried, 2) fresh whole saliva, left wet, or 3) moisture from a humidity chamber. All contamination conditions were tested for sealant bond strength with and without the bonding agent as an intermediate layer under the sealant. As controls, both sealant and bonding agent under sealant also were applied to clean etched enamel. Bond strength was measured using a universal testing machine. Data were analyzed using a two-way ANOVA. Under conditions of humidity or intact saliva, sealant alone showed significant reduction in bond strength (P less than 0.001). Bonding agent under sealant on wet contamination yielded bond strengths equivalent to the bond strength obtained when sealant was bonded directly to clean, etched enamel. Bonding agent used without contamination yielded bond strengths significantly greater than the bond strength obtained when using sealant alone without contamination (P less than 0.001). When the saliva was air dried onto the surface, there was no significant difference in bond strengths whether or not a bonding agent was used under the sealant.