Experimental intra-oral caries models in fluoride research.

The use of experimental intra-oral caries models has increased in fluoride research. This paper focuses on the pre-clinical intra-oral models, the in situ and in vivo models, the various types, their benefits and disadvantages. Both preparation and sterilization of the hard tissue substrates can affect the substrates and therefore the results. Care needs to be taken that dentine samples are not exposed to drying and consequently shrinking during preparation and evaluation. Sterilization by gamma-radiation is at present the least tissue-damaging method. The most realistic experimental model is the in vivo model, followed by the in situ model using specimens with natural surfaces. The most accurate and direct evaluation technique for demineralization and remineralization studies is quantitative transversal microradiography, whereas confocal laser scanning microscopy (CLSM) is the most sensitive qualitative evaluation technique. Other evaluation techniques discussed are microhardness testing and the iodine permeability test. In light of the present skewed caries situation in western countries we suggest that fluoride research focuses on experimental caries models that can mimic severe cariogenic challenge. Testing of fluoride combinations and dosages that can prevent lesion development rather than promote remineralization would then be a practical consequence.