A suitable base material for composite resin restorations: Zinc oxide eugenol

ObjectiveThis in vitro study evaluated the effects of a zinc oxide eugenol (ZOE) base on the mechanical properties of a composite resin restoration.MethodsClass I cavities were prepared on plastic teeth and filled with ZOE plus composite resin, following standard clinical procedures. The samples were sectioned sagittally and the ZOE–resin interface was exposed. After polishing, nanoindentation was performed on the region near the interface, and elastic modulus and hardness were plotted in the form of a color contour map. SEM was employed to observe the interface between composite resin and ZOE base.ResultsIn the region close to the ZOE base, the elastic modulus and hardness of composite resin reduced to the values of 9.71 ± 0.54 and 0.51 ± 0.05 GPa, respectively. Eugenol from ZOE had detrimental effects on the composite resin only to a distance of less than 100 μm from the ZOE base.ConclusionAlthough eugenol suppresses polymerization slightly, by considering the biological advantages of ZOE, together with the results of the current investigation, ZOE may still be considered a suitable base material for composite resin. Bonding is essential for composite resin restorations over ZOE bases to avoid shrinkage detachment.