Technical advances in intra-oral model systems used to assess cariogenicity: experimental design and analysis...

In situ cariogenicity-testing models must show evidence of compliance with valid clinical parameters, and this has been achieved with respect to pyrophosphate-, monofluorophosphate-, and zinc citrate trihydrate-containing dentifrices, where earlier in vitro studies failed to predict clinical efficacy. Parameters for validity testing should include the use of enamel fluoride uptake, plaque and/or saliva fluoride assessments, re-/demineralization assays of appliance-borne enamel slabs or slices, and plaque microbial, biochemical, and pH studies. Model reliability must be capable of withstanding repeat calibration experiments where the dosage, frequency of application, and/or duration of exposure to a new product may be varied. Furthermore, the number of enamel slabs/slices carried per appliance (and the number of artificial caries lesions per enamel insert) requires to be defined. Such studies should be repeated, but whether in the same or different subjects, or with or without cross-over, has to be determined. However, the capability of reproducing a clinically proven dose-response is essential. Models must be sensitive enough to detect changes in any test product F-concentration, but only equivalence claims should be permitted. Thus, superiority cannot be established, since accuracy may not be assumed beyond the upward limits of a clinically validated range. Finally, models should not be so exclusive in design as to preclude independent verification of their findings.