Effect of ZnCl2 on plaque growth and biofilm vitality

Objective: The aim of this study was to evaluate the effects of ZnCl2 on plaque-growth and vitality pattern of dental biofilm and to determine the optimum zinc concentration for the inhibition of plaque formation. Design: Data were collected from nine volunteers for whom a special-designed acrylic appliance was prescribed after a careful dental check up. The volunteers rinsed twice daily for 2 min with ZnCl2 of 2.5, 5, 10, 20 mM as treatment and double distilled water (DDW) as control in respective assigned test weeks. The plaque index (PI) was assessed after 48 h of appliance wearing. The glass discs with the adhered biofilm were removed from the splints and stained with two fluorescent dyes. The biofilm thickness (BT) and bacterial vitality of the whole biofilm as well as the mean bacterial vitality (BV) of the inner, middle and outer layers of biofilm were evaluated under confocal laser scanning microscope (CLSM). Results: PI, BT and BV of biofilms treated by various concentrations of ZnCl2 were reduced significantly when compared with the DDW group (p < 0.05). PI, BT and BV of the 2.5 mM ZnCl2 group was significantly higher than groups of 5, 10, 20 mM ZnCl2 (p < 0.05). The mean BV of the 3 layers (inner, middle and outer layers) showed that 2.5 mM ZnCl2 was the lowest concentration to inhibit BV in the outer layer, 5 mM was the lowest concentration to extend this inhibition of BV to the middle layer, and none of the concentrations investigated in this study has shown any effect on bacteria inhibition in the inner layer. Conclusion: Zinc ions exhibited possible inhibitory effects on plaque formation, and have a promising potential to be used as an antibacterial agent in future dentifrices and mouthrinses. (C) 2011 Published by Elsevier Ltd.