An in situ enamel section model for assessment of enamel re/demineralization potential

Abstract

An enamel-section-carrying intra-oral appliance to predict the results of double-blind anti-caries studies has been developed. Initial validation was against the F concentration effect attained in a clinical trial where three sodium monofluorophosphate (SMFP) dentifrices were used. Original appliance-based work showed significant differences in remineralization between non-F and F dentifrices, but not between different F dentifrices. However, it was shown later that acidified gel-prepared lesions were not as responsive as solution-prepared lesions to de- and remineralizing processes, and lesion remineralization rates were found to be dependent on initial lesion size. An in situ cross-over study was then repeated with use of acid-solution-created lesions, and seven volunteers completed the project. Each brushed twice daily x 2 min with either 0, 1000, or 2500 ppm F, as SMFP dentifrice. After a two-week wash-out, subjects wore the appliances for four weeks. Enamel mineral content was assessed at 0, two, and four weeks via microradiography/microdensitometry, and a statistically significant dose-response was obtained between non-F and F as well as between 1000 and 2500 ppm F pastes, i.e., as per the three-year clinical trial data. Hence, the model's suitability for pre-clinical screening was confirmed. It has also been used in caries microbiological studies, in root caries investigations, and currently in chewing gum cariogenicity experiments.