A Cochrane review included three studies with a total of 432 randomised lesions (137 participants). Pooling of data was not appropriate or attempted. Individual studies showed inconsistent effects of ozone on caries, across different measures of caries progression or regression. Given the high risk of bias in the available studies and lack of consistency between different outcome measures, there is no reliable evidence that application of ozone gas to the surface of decayed teeth stops or reverses the decay process.
Comment: The quality of evidence is downgraded by imprecise results (limited study size for each comparison), by potential reporting bias and by inconsistency (heterogeneity in interventions and outcomes).