In vitro shear bond strength of adhesive to normal and fluoridated enamel under various contaminated conditions

Objective: This study examined the shear bond strength of bonding agents to normal or fluoridated enamel following use of weak or strong acids to prepare enamel surfaces and after contamination with a measured amount of saliva at various stages of the bonding procedure. Method and materials: One hundred extracted human third molar teeth were randomly separated into 2 basic groups (normal or fluoridated teeth), then divided into 5 subgroups. Group A specimens were not contaminated. After etching, enamel surfaces were dry and clean. Group B was left with wet surfaces after etching. Group C specimens were contaminated with artificial saliva and then dried. Group D specimens were contaminated with artificial saliva, rinsed, and then dried. In group E, all enamel surfaces were left contaminated with saliva after the etching procedures (with maleic acid or phosphoric acids). Adhesive resins were applied to all enamel surfaces according to the manufacturer's instructions. The specimens were then mounted and tested to determine shear bond strength. Results: If normal enamel surfaces were rinsed and dried immediately after contamination, there was no significant reduction of shear bond strength of adhesive to enamel. Specimens in group E and group C had significantly lower bond strengths than did control specimens (group A). In the fluoridated groups etched with the phosphoric acid, statistically significant reductions in bond strengths were obtained in all contamination groups and in the control group. In the fluoridated specimens, there were no statistically significant differences between any of the contamination groups and the control group when maleic acid was used. Conclusion: Saliva contamination may not be a risk factor for successful bonding between bonding agent and dental tissues for normal or fluoridated enamel surfaces if they are rinsed and dried immediately after contamination. Etching of normal enamel surfaces with phosphoric acid in the presence of contamination may provide higher shear bond strength than etching with maleic acid.