Method: For this in vitro study, 54 non-carious molars were ground down to dentin and sectioned along the mesial-distal axis. One half of each tooth served as a control, while the other half was artificially eroded with a pH-cycling. The specimens were randomly assigned to one of three adhesive systems: 1) Optibond FL; 2: Clearfil SE Bond; 3: G-Bond (GB). Thirty molars (n=10/group) were analysed for bonding wettability using a device for static (SCAM) and dynamic contact angle (DCAM) measurements. The other 24 molars (n=8/group) were bonded with one of the three adhesives and a composite build-up was placed. Afterwards the specimens were sectioned into beams of 1x1mm2 and underwent a micro-tensile test. Differences between the groups regarding contact angle measurements were analysed with nonparametric two-way ANOVA analysis and Wilcoxon Rank Sum Test. Differences regarding bond-strength measurements between the groups were analysed with a linear mixed model. All analyses were corrected for multiple testing (Bonferroni-Holm) and level of significance was always set at a=0.05.
Result: There were clear differences between eroded and non-eroded surfaces regarding wettability and bond strength. Erosion (p<0.01) and adhesive (p=0.01) had both a significant influence on SCAM. Regarding DCAM there was a difference for both angles: whereas erosion (p<0.001) and adhesive (p=0.02) were significant for the receding contact angle, for the advancing contact angle only erosion (p<0.001) and the interaction between erosion and adhesive (p=0.02) had a significant effect on the results. Bond-strength measurements were significantly influenced by erosion (p=0.02) but not by the adhesive (p=0.57).
Conclusion: There seems to be a strong correlation between poor bonding performance on eroded dentin and lower wettability properties of the adhesive systems on these altered surfaces.