Antibacterial Effect of Two Nano Zinc Oxide Gel Preparations Compared to Calcium Hydroxide and Chlorhexidine Mixture

The aim of this study was to compare the antibacterial effects of two gels
containing zinc oxide and zinc oxide/silver nanoparticles and a mixture of calcium hydroxide
and 0.12% chlorhexidine as intracanal medicaments in root canals contaminated with
Enterococcus faecalis (E. faecalis) at different time intervals. Methods and Materials: After
preparation and culturing of E. faecalis in 132 single root teeth, the initial count of bacteria was
performed. Then, different materials as intracanal medicaments were used in periods of 3, 7 and
14 days (group 1: calcium hydroxide with 0.12% CHX paste; group 2 zinc oxide nanoparticles
gel; group 3: zinc oxide/silver nanoparticles gel; group 4: normal saline as the control group).
After the specified time, intracanal medicament was removed and the final count of bacteria was
performed. Antibacterial effect of materials was counted by measuring the percentage reduction
in the colony counts (RCC). Data were analyzed using the descriptive statistics (Mean±SD) and
multi-factorial analysis of variance (by taking into account the effect of the time factor on the
dependent variable). Results: There were no statistically significant differences among mean RCC
of different time intervals in each group (P=0.09). However, the differences in mean RCC of
different dressing materials were significant (P<0.001). The effect of interaction between time
and materials was significant (P=0.015). Comparison of the antibacterial effects of experimental
agents at different time intervals showed that the mean RCC in group 1 was higher than other
groups (P<0.001). The difference in antibacterial effect between groups 2 and 3 was not
significant (P>0.05). The minimum antibacterial effect was observed in group 4 (P<0.0001).
Conclusions: The mixture of calcium hydroxide/chlorhexidine as an intracanal medicament was
more effective than zinc oxide and zinc oxide/silver nanoparticles gels.