Effect of eugenol exposure time and post-removal delay on the bond strength of a self-etching adhesive to dentin

This study evaluated the effects of the exposure time of eugenol-based provisional restorative material and the time elapsed between the provisional material removal and the adhesive procedure on the bond strength of the composite to dentin. Human third molars were sectioned into two halves that were enclosed in resin cylinders. The cavities were prepared over the buccal/lingual faces with diamond burs. Zinc oxide and eugenol (ZOE) provisional material was inserted into cavities and left for 24 hours, 7 days or 14 days. The cavities not restored with ZOE were used as controls. After ZOE removal or over fresh dentin (control), self-etching Adper SE Plus was applied immediately, after a 7- or 14-day delay. The cavity was restored with non-eugenol provisional material during this delay period. Cylinders of resin cement were built-up over the hybridized dentin. A shear load was applied to the cylinders at a crosshead speed of 0.5 mm/minute until failure. The data were statistically analyzed using two-way ANOVA and Tukey's tests (α=0.05). Using IRM as a provisional restoration for 24 hours followed by its removal and immediate adhesive application resulted in the lowest values of shear bond strength. There was no significant difference between the other experimental conditions. The use of IRM for 24 hours adversely affected the shear bond strength of a self-etching adhesive to dentin. The recovery of the proper bond strength occurred one week after IRM removal.