Long term bonding performance of contemporary and experimental self-etching adhesives

Objectives: The objective of the present study was to evaluate the long-term bonding performance of two commercial self-etching systems (SESs) and one experimental SES using a PCR thermal cycler. Methods: Twelve human third molars were used in this study and every four teeth were randomly assigned to each system. The adhesives employed were two commercial all-in-one SESs, CLEARFIL TRI-S BOND (TriS, Kuraray), BeautiBond (SHOFU), and one experimental all-in-one SES, MTB-200 (Kuraray). BeautiBond was a HEMA-free adhesive, whereas TriS and MTB-200 were HEMA-contain adhesives. MTB-200 also incorporated hydrophobic monomers. After removal of crown segment, #600 SiC paper was employed to polish the dentin surface under water. Then the adhesives were applied following the instruction of each manufacture and followed by the resin composite build-up. After storage in 37oC distilled water for 24 hours (1day) or in PCR thermal cycles for 20,000 times (TC20k), the specimens were sectioned into the beams with the cross sectional area 1.0mm2 for the micro-tensile bond strength test (MTBS) at a crosshead speed of 1mm/min. The obtained data were expressed as MPa and statistically analyzed with one-way ANOVA and Tukey HSD test. Results: The mean±SD of MTBS in descending order were: 72.52±17.17 (MTB-200, 1day), 69.70±19.30 (MTB-200, TC20k), 64.78±14.19 (TriS, 1day), 58.71±12.86 (TriS, TC20k), 31.03±17.08(BeautiBond, 1day), 26.89±14.78 (BeautiBond, TC20k). In statistical analysis, MTB-200-1day showed a significantly higher MTBS (p<0.05) than the TriS-TC20k. Conclusion: Newly developed SES (MTB-200) showed comparable or better bonding performance compared to marketed SESs over time.