Method: 36 Human molars stored in 0.5% chloramine T were cut in half and prepared with a flat enamel surface. Each tooth will represent one of 6 groups. A) 37% H3PO4 etch for 20 seconds. B) 37% H3PO4 etch rubbed into enamel for 20 seconds. C) 5.25% NaOCl for 30 seconds and 37% H3PO4 etch for 20 seconds. D) 5.25% NaOCl for 30 seconds and 37% H3PO4 etch rubbed into enamel for 20 seconds. E) 5.25% NaOCl for 60 seconds and 37% H3PO4 etch for 20 seconds. F) 5.25% NaOCl for 60 seconds and 37% H3PO4 etch rubbed into enamel for 20 seconds. A rinse step was performed between NaOCl and etching, and after etching. The surfaces were dried and 1 coat of Optibond FL adhesive was applied and light cured for 20s. A composite build-up of approximately 5 mm was made using Filtek Supreme, applied in 2 increments. After 24-hour storage in water, the specimens were sectioned with a diamond saw in both the x and y directions. Each rectangular stick had a cross section area of approximately 0.8mm. At random 2 sticks from each tooth were subjected to tension at a crosshead speed of 1.0 mm/minute using a Zwick testing machine after 1 week and 3 months of storage in artificial saliva at 37oC.
Results: One-ANOVA (alpha 0.05) revealed no statistically significant differences between groups ( p> 0.05).
Bond strength in MPa (SD)
A 39.5 (5.9)
B 33.7 (10.4)
C 32.3 (13.5)
D 33.2 (16.6)
E 27.8 (14.2)
F 32.8 (14.5)
Conclusion: The addition of NaOCl did not increase the long-term bond strength of composite to enamel.
Keywords: Acid etch, Dental materials and Enamel
See more of: Dental Materials 1: Adhesion - Bond Strength Testing and Mechanisms