Effect of zinc-doping in physicochemical properties of dental adhesives

To evaluate changes in the physicochemical properties, water sorption (WS), solubility (SO), modulus of elasticity (E), ultimate tensile strength (UTS), and microhardness (MH) tests were undertaken in zinc-doped dental adhesives.

Two bonding resins, Adper Single Bond Plus (SB) and Clearfil SE Bond (SEB), were zinc-doped by mixing them with 5, 10 or 20 wt% of ZnO powder, or with 1 or 2 wt% ZnCl2. Resin disks were made of each adhesive blend for the evaluation of WS, SO, and MH, and dumbbell-shaped specimens were prepared for E and UTS testing.

An increase in WS and SO was observed for adhesives doped with ZnCl2. A reduction in WS was observed for the adhesive blends containing 10% or 20 wt% ZnO, while the SO was not altered in any of the ZnO-doped adhesives. An increase in E values was observed only for the SB adhesive doped with ZnCl2. For SEB-blends, the incorporation of zinc compounds did not alter the E values. UTS values decreased when SEB was doped with ZnO. SB-blends doped with 20 wt% ZnO significantly increased their MH, and the addition of zinc to the SEB-blends augmented the MH values in all cases.