Objective: Coverage of exposed roots with adhesives is one of the possible options to prevent root surface caries. The purpose of this study was to compare the bonding abilities of current self-etch adhesives to cementum. Materials and methods: Three commercial self-etch adhesives: Clearfil Protect Bond (PB, Kuraray Medical), Clearfil Tri-S Bond (S3, Kuraray Medical), and Adper Prompt L-Pop (AD, 3M ESPE) were used. Resin composite was bonded to the cementum surface of human extracted teeth using each adhesive according to the manufactures' instructions (n=7). After storage in water at 37°C for 24 hours, the specimens were sectioned and trimmed into an hourglass shape to produce an approximately 1 mm
2 area at the adhesive-cementum interface, and subjected to the microtensile bond strength (MTBS) testing at a crosshead speed of 1 mm/min. The fractured surfaces were observed using SEM to determine the mode of failure. The morphology of the etched cementum surfaces and the adhesive-cementum interfaces was also examined under SEM. Results: The MTBS in MPa were 23.4±7.2 for PB, 24.8±7.1 for S3, and 25.9±7.2 for AD. No significant differences were observed among the three adhesives (p>0.05, ANOVA). Mixed failure (adhesive and cohesive in cementum) was the predominant for all the specimens tested. SEM observations of the etched surfaces revealed deeper depressions by the application of AD compared with S3 and PB, reflecting the acidity of each of the primers/adhesives. The thickness of hybridized layers produced was 2-4 µm for PB and S3, and 7-10 µm for AD. Conclusion: The three self-etch adhesives demonstrated similar bond strengths to cementum, although thicker hybridized layer was formed by AD with greater aggressiveness in etching.
Supported by a Grant-in-aid for Scientific Research (16390545) from the Japan Society for the Promotion of Science.