The use of ozone in dentistry: Part 3

Nagayoshi et al. (6) have studied the efficacy of three different concentrations of ozone water (0.5, 2, and 4 mg/ml in distilled water) on the time-dependent inactivation of cariogenic, periodontopathogenic and endodontopathogenic microbes (Streptococcus, Porphyromonas gingivalis and endodontalis, Actinomyces actinomycetemcomitans, Candida albicans) in culture and in biofilms. Depending on the dosage, the oral microbes were inactivated after 10 seconds. Anaerobes were particularly sensitive to ozone. Candida was more resistant (approx. 90% reduction after incubation with the highest ozone concentration).

Baysan et al. (10) have studied the antibacterial effect of ozone gas (HealOzone) on moist lesions of primary root caries (0.25% ozone in air with a gassing rate of 13.3 ml/sec.) in freshly extracted human teeth in vitro. 40 soft lesions were divided into two groups, in order to compare the efficacy of 10 and 20 seconds of exposure to ozone. Each lesion was first divided into two halves using a sterile blade; one half was exposed to ozone, the other half was left as a control. Both types of sample were then put in an anaerobic culture medium and incubated for 4 days at 37°C. In the samples treated with ozone gas, the microbe concentration was significantly and time-dependently reduced.

Nagayoshi et al. (11) used dentin blocks from cows’ teeth to study the role of bacteria in endodontal infections and caries. Colonies of Enterococcus faecalis and Streptococcus mutans were co-incubated with sterilized dentin blocks for 6 days. The root canals of the infected dentin blocks were either irrigated with ozone water for 10 minutes or treated with ozone water plus ultrasound; as a control, they were also treated with distilled water with and without ultrasound. Sodium hypochlorite (NaOCl; 2.5%, i.e. the clinical concentration) was used as a reference disinfectant; it eliminated all living bacteria in the dentin. Ozone water reduced the amount of streptococci and enterococci in the dental tubules; when ozone was combined with ultrasound treatment, more than 90% of the bacteria were killed. From these results, the authors have concluded that ozone water can be considered to be a potential root canal disinfectant that is less cytotoxic than NaOCl. NaOCl can cause necrosis while ozone water is exceptionally biocompatible (12). Steier and Steier have suggested combining a less cytotoxic concentration of NaOCl (1.25%) with ozone13.
The results of Nagayoshi et al.11 have been confirmed by Huth et al. (2008)14 in a root canal culture model (biofilm formation after incubation of teeth with Pseudomonas aeruginosa, Enterococcus faecalis, Peptostreptococcus micros and Candida albicans): Depending on the dose and species, ozone gas and/or ozone water reduce the amount of bacteria.

Lynch and Swift (2008) (15) have acknowledged the published information on the role of ozone as an optional, complementary root canal disinfectant and concluded that “as ozone is the most powerful antimicrobial and oxidant we can use in endodontics, and as aqueous ozone revealed the highest level of biocompatibility compared with commonly used antiseptics, then it is fairly obvious that ozone should be used to help combat the microorganisms associated with infected root canals”.