Intra-Oral Model

Intra-Oral Caries Models
for Evaluation Anti-caries Efficacy of Fluoride Products

Field of Application: Preventive Dental Products Testing

Marketplace: Manufacturers of caries-preventive therapeutic agents are now obligated to obtain confirmation of their fluoride product claims for the FDA and often times voluntarily seek approval from the ADA. This approval, requires studies to determine product efficacy. Manufacturers' primary problem in seeking this approval is the cost of clinical trials, which has resulted in their searching for statistically efficient and effective alternatives. Intra-oral models have been utilized for investigating the dynamics of enamel and dentin caries and to predict the efficacy of therapeutic agents, such as fluoride. The major challenge for manufacturers is to utilize a model that has been validated and deals with the inherent variables within the oral environment by addressing the following issues:

  • biological variability and complex interaction of cariogenic and cariostatic factors within the oral environment;
  • similarity between model results and clinical conditions the model is designed to represent; and
  • ability to demonstrate statistically significant, dose-response differences in the efficacy of products containing different amounts of fluoride.

Technology Research and Development Description: The  Interproximal model and the Buccal model  have been developed and validated for studying the effect of fluoride-containing products on changes in enamel mineral content, as well as fluoride uptake into incipient enamel lesions. The interproximal model involves placing enamel cores in specially constructed partial dentures of study volunteers. Dental plaque forms a space between volunteers natural tooth and the appliance. The buccal model involves placing gauze covered enamel specimens in the bucal flange area of volunteer's partial denture. The gauze encourages the formation of plaque of uniform thickness.

Market Advantage: IUSD researchers have demonstrated statistically significant improvements in their in situ interproximal and buccal models. Relative efficacy of the fluoride dentifrices tested in this published study was similar to that established in clinical trials, and, therefore, supports the use of these models for in situ studies of the effects of fluoride-containing products on enamel lesions. Other advantages serve to validate this model in the following terms:

  • demonstration of a dose response for both enamel fluoride uptake and enamel changes;
  • measurement using surface microhardness and/or transverse microradiography;
  • OHRI compliance with FDA Good Laboratory Practices.

Scientist:  Domenick Zero, DDS,MS
                 Director, OHRI 

Technical Documentation:

In situ caries models. Adv Dent Res 9:214-230 (1995), D.T. Zero.

Response of a de/remineralization in situ caries model to fluoride dentifrice. Caries Res 28:208, Abst 99 (1994), D.T. Zero, J.D.B. Featherstone, J. Fu, Al> Hayes, G.L. Vogel.

An improved intraoral enamel demineralization test model for the study of dental caries. J. Dent Res 71 (Spec Iss):871:878 (1992), D.T. Zero, J. Fu, K.M. Anne, S. Cassata, S.M. McCormack, L. M. Gwinner.

Comparison of the iodide permeability test, surface microhardness test and mineral dissolution of bovine enamel following acid challenge. Caries Res 24:181-188 (1990), D.T. Zero, I. Rahbek, J.Fu, H.M. Proskin, J.D.B. Featherstone.

An in situ Interproximal Model for Studying the Effect of Fluoride on Enamel. Caries Research, 1997;31:60-70., AJ Dunipace, AF Hall, SA Kelly, AJ Beiswanger, GM Fischer, LL Lukantsova, GJ Eckert, GK Stookey;