Importance of model parameters in the assessment of intra-oral remineralization

Since the introduction of the Intra-oral Cariogenicity Test by Koulourides et al. (1974), many groups around the world have been developing and using intra-oral models to test new caries-preventive products, as well as to study physiological processes in the oral cavity. In spite of the large numbers of papers reporting these methods, very little research has been done to determine the importance of the many variable parameters which influence the performance of these models. Among these, the following can be identified: (a) panelist criteria, (b) the use of sound vs. pre-demineralized enamel of human or bovine origin, (c) the use of gauze or a recess to accumulate plaque, (d) the method to create incipient lesions, (e) the duration of the experiment, (f) the number of panelists required for statistical significance to be obtained, (g) the assessment techniques for mineral and/or fluoride uptake/loss, and (h) the choice of contralateral, 'cross-over', or 'monadic' experimental designs. Our results, supported by data from the literature, indicate that the choices made with respect to these parameters are of paramount importance in determination of the outcome of the respective study.