Microbicidal effect of ozone gas in vitro: interaction with organic compounds and endodontic irrigation agents

Masako Nakano, DMD, PhD,a Ayuko Takao, DMD, PhD,b Toshiko Ozawa, DMD, PhD,a Tomokazu Igarashi, DDS, DDSc,b Nobuko Maeda, DDS, DDSc,b and Noriyasu Hosoya, DMD, PhDa

aDepartment of Endodontology, and bDepartment of Oral Microbiology, Tsurumi University School of Dental Medicine, Yokohama, Japan

Purpose: The aim of this study was to estimate the utility of an ozone gas generating apparatus (HealOzone) for endodontic treatment by its bactericidal efficiency in vitro.
Materials and Methods: Water- or TS broth-suspended microorganisms (Streptococcus mutans, Lactobacillus casei, Enterococcus faecalis, and Candida albicans) were exposed to ozone gas for up to 80 s. Serially diluted irrigation agents (H2O2, NaOCl) and E. faecalis were incubated at room temperature for a minute with or without ozone exposure (20 s). In both experiments, survived microbes were determined by semi-quantitative cultivation.
Results: Eighty second-exposure of ozone gas completely killed the microorganisms suspended in water. However, this treatment had no effect on the same microorganisms suspended in the culture broth, which contained the organic compounds. Combination of ozone gas exposure and H2O2 solution showed synergic effect to kill E. faecalis in water, but not in the broth. In contrast, ozone inhibited the bactericidal effect of diluted NaOCl solution against E. faecalis in water.
Conclusion: Based on the experimental results, probability of sterilization effect of ozone gas either used with or without root canal irrigation agents was doubtful.(Asian Pac J Dent 2012; 12: 21-26.)

Key Words: Healozone, hydrogen peroxide, microbicidal effect, ozone gas, sodium hypochlorite