Effect of nanohybrid layer forming adhesives on dentin

Objective: To evaluate the effect of three nanohybrid layer forming adhesives on the molecular composition of dentin. Methods: The materials tested were i-Bond (IB), G-Bond (GB) and Clearfil S3 Bond (S3). Dentin surfaces prepared by horizontal sectioning the coronal part of extracted intact third molars were polished with SiC papers to 1000 grit size. The surfaces were imaged and analysed by reflection FTIR microscopy, employing FTIR molecular mapping and line scan analysis before and after 30 s application of the adhesives followed by rinsing the treated surfaces with water ethanol and acetone to remove soluble salts and resin components. The treated surfaces were compared with their native controls and the difference spectra with the spectra of the corresponding adhesives. Three regions (400x300 ìm) were analyzed on each of the three dentin sections used per material. The extent of the dentin demineralization was calculated from the mineral (v P-O, 1064 cm-1) to matrix (v C=O, amide I 1655 cm-1) ratios of the treated surfaces relative to their individual controls. Results: The extent of demineralisation at the uppermost dentin surface was (mean±SD): IB:40.3±2.2%, GB: 22.6±1.2%, S3: 18.3±2.4% . GB and S3 demonstrated significantly lower decalcification from IB. Subtraction spectra showed no band shifts to support development of primary bonding. Some minor peaks detected at 1720 cm-1 (v C=O) after ethanol rinsing were diminished after acetone rinsing. Conclusion: All the adhesives tested induced a mild to weak demineralisation pattern on the adhesive surfaces, without evidence of primary bonding.