Curing Efficiency of All-in-one Adhesives

Objectives: Modern all-in-one adhesives may be used on substrates like dental alloys, ceramics and polymers for resin bonding and repair purposes. However, such surfaces demonstrate minimal neutralization capacity compared to enamel and dentin. The aim of the present study was to evaluate the curing efficiency of three all-in-one adhesives placed on dentin and on an inert substrate. Methods: The products tested were Clearfil S3 (S3), iBond (iB) and G-Bond (GB). The adhesives were applied, in thin films, on coronal human dentin specimens, polished up to 1200 grit size SiC papers and on glass slip covers, cured for 20s (standard mode, 750 mW/cm2) and rinsed with ethanol to remove the oxygen inhibition layer. Three specimens were prepared from each adhesive on each substrate. The curing efficiency was measured by micro MIR-FTIR spectroscopy. ANOVA was used to assess the statistically significant differences at an a=0.05 level. Results: The amount of remaining C=C bonds (%RDB) on dentin (D) and on glass (G) were as follows (mean + SD): iB(D):58.45+2.42, GB(D):46.08+1.90, S3(D):36.85+2.04, iB(G):62.22+2.25, GB(G):69.25+2.7 and S3(G):54.68+3.22. All the adhesives showed higher % RDB on glass surfaces than on dentin (p<0.05). S3 showed the lowest %RDB followed by GB and iB in both conditions. Conclusions: Setting of the tested adhesives was inhibited on inert surfaces compared to dentin. Neutralization of the acidic adhesive components seems to contribute to the improved conversion monitored on dentin surfaces. Based on the low conversion values, it seems that the all-in-one adhesives may not be compatible to substrates with low acid neutralization capacity.