Treatments to halt or reverse the progression of non-cavitated caries lesions are of increasing interest. Diagnostic technologies under development offer potential for the assessment of gradual progression and regression of such lesions. Many therapies directed at correcting demineralization-remineralization imbalance should, in principle, protect enamel similarly across lesion severities from initiation to near cavitation. If this is so, and if acceptable reproducibility and predictive validity can be demonstrated for a diagnostic of acceptable cost, then clinical trials of agents to prevent cavitation can become more efficient by the use of outcome indices that reflect, in addition to cavitation, the expansion and regression of non-cavitated lesions. However, to achieve such a benefit will require data analyses that fully exploit ordinal or continuous-scale outcome measures. We consider comparison of such measures of lesion status between treatment groups, with most attention to ordinal categorical data. Interim data from a clinical trial in Lithuanian children are used for illustration.