Evaluation of the Sensitivity of Selected Candida Strains to Ozonated Water—An In Vitro Study

Background: oral thrush and the search for a gentler antiseptic

Candida yeasts, and Candida albicans in particular, are a common cause of oral fungal infection (oral candidiasis, or oral thrush). They tend to become a problem under dentures and in people whose immune defences are lowered. Chlorhexidine gluconate is the antiseptic mouthrinse most dentists reach for, but prolonged use can stain teeth, alter taste and raises longer-term concerns about tolerance. That has prompted interest in ozonated water as a possible alternative, because ozone has broad antimicrobial activity and breaks down into ordinary oxygen without leaving a chemical residue behind.

Study design: three Candida strains tested in the laboratory

This was an in vitro study, meaning the work was carried out on cultured yeast in the laboratory rather than in the mouths of patients. It is not a clinical trial. The researchers tested three reference strains of Candida grown from culture collections: Candida albicans, Candida glabrata and Candida krusei. Each was exposed to ozonated water at three concentrations (5, 30 and 50 micrograms per millilitre) for three contact times (30, 60 and 120 seconds). The number of surviving yeast cells was measured using the MTT assay, a standard colorimetric method that gauges how many cells remain viable. A 0.2% chlorhexidine gluconate solution was used as the comparison, and the results were analysed statistically using analysis of variance with Newman-Keuls post-hoc testing.

Findings: viable Candida cells fell with concentration and contact time

Ozonated water reduced the number of viable Candida cells across all three strains. The effect grew stronger as the concentration increased and as the contact time lengthened. The largest reduction was seen in Candida albicans, where roughly 35% of cells were no longer viable after 120 seconds at the highest concentration of 50 micrograms per millilitre. Across the strains, the sensitivity of Candida to ozonated water was comparable to that seen with 0.2% chlorhexidine gluconate.

What the authors concluded

The authors concluded that, within the limits of their experiment, the selected Candida strains were sensitive to ozonated water at all of the concentrations tested, and that this sensitivity increased with both concentration and application time. Because the effect was broadly comparable to chlorhexidine gluconate, they suggested that ozonated water may be worth exploring further as an adjunct antifungal option in dentistry.

Limitations of this study

This is laboratory work and its reach is limited. The study used a small number of reference strains grown in the dish rather than the mixed communities of microbes found in a real mouth, and it tested single-species suspensions rather than the sticky biofilms that form on teeth and dentures. Only three concentrations and three contact times were examined, over a single treatment. It did not reproduce the conditions of a living mouth, such as saliva, body temperature and the constant flow that would dilute and disperse an applied solution. Crucially, an in vitro result cannot show whether rinsing with ozonated water actually treats or prevents oral thrush in people; that would require controlled clinical trials. The findings are best read as an early, mechanistic signal rather than evidence of clinical benefit.