Shear Bond Strength of Self-etching Bonding Agents to Etched and Unetched Enamel

Self-etching bonding agents bond well to dentin but their bond to enamel has been questioned.  Some clinicians have advocated a selective enamel etch to improve the enamel bond with self-etching adhesives. Objective: This study measured the shear bond strength to enamel of two self-etching bonding agents when the enamel was etched for 10, 20 or 40 seconds compared to no etch.  Methods: 80 recently extracted teeth were ground with abrasive discs ending at 320 grit to provide a uniform enamel bonding area.  Prompt L-Pop and Clearfil SE Bond were applied to this flattened area according to the manufacturers’ directions. After curing the bonding agent, a tube of Z-250 (Shade A2) composite resin was applied over the bonding agent.  The composite was cured for 20 seconds and the tube removed.  After storing the specimens in deionized water for 24 hours, they were debonded in shear in an Instron at a 5mm/minute crosshead speed at a 5 mm/minute crosshead speed.  Peak failure loads were converted to shear bond strength by dividing by the area. Groups were examined for intergroup differences using 2 factor ANOVA and Tukey B post hoc analysis.  Mean shear bond strengths are shown below in MPa. (n= 12). 

Results: Material                        enamel etch                  Shear Bond Strength  Standard deviation

Conclusions: Shear bond strength of Clearfil SE Bond is significantly greater than Prompt L-Pop (p=.01).  Selective enamel etch may be helpful clinically.