An Improved Intra-oral Enamel Demineralization Test Model for the Study of Dental Caries

Abstract

The intra-oral enamel demineralization test (IEDT) was introduced by Brudevold et al. (1984). This caries model involves human subjects wearing palatal appliances each holding eight bovine enamel blocks covered by a bacterial cell layer prepared by the harvesting of cultures of Streptococcus mutants (test plaque). The original model used the iodide permeability test for assessment of the extent of demineralization of bovine enamel blocks resulting from acid production by the test plaque after dietary substrate challenge. The IEDT model has been expanded and improved by us in the following ways: (1) Based on encouraging findings from an in vitro study (Zero et al., 1990), the surface microhardness test has been adopted to measure the extent of demineralization occurring at three sites on the enamel blocks corresponding to an area over which the effective plaque thickness is 0.5, 1.5, and 2.5 mm; (2) intra-oral pH of the test plaque is measured by means of a Beetrode miniature pH electrode at baseline, then at five, 10, 15, 30, and 45 min after the start of a test; (3) plaque samples are collected at the end of a test and analyzed for organic acid content by means of HPLC; (4) the bacterial test challenge has been expanded to include different cariogenic bacteria which are grown under various growth conditions. The improved model has the capability of studying fundamental aspects of the caries process, namely, the relationships among dietary substrate challenge, plaque pH change, plaque organic acid profiles, microbial virulence properties, and enamel demineralization. Furthermore, the model has the potential for use in more applied research on caries-preventive agents such as fluoride.

l -Arginine Modifies the Exopolysaccharide Matrix and Thwarts Streptococcus mutans Outgrowth within Mixed-Species Oral Biofilms

“…Our data reveal that defective assembly of EPS matrix and microcolony formation as a result of L-arginine exposure may also contribute to elevated in situ pH at the biofilm-sHA interface. Previous studies have shown that EPS-enmeshed microcolonies could trap acid at the sHA surface and/or restrict the access of neutralizing buffer to generate acidic microenvironments locally due to metabolic activity of the densely packed bacteria enmeshed within a diffusionlimiting EPS matrix, particularly at the deeper layers of the biofilm (6,57,58). Altogether, it appears that the combination of ADS activity and favorable ecological changes with disruption of EPS/ microcolony development may offer a more comprehensive explanation for the biofilm pH-related effects associated with L-arginine exposure.…”

Biochemical Composition and Cariogenicity of Dental Plaque Formed in the Presence of Sucrose or Glucose and Fructose

“…Thus, Dibdin and Shellis [1988] suggested that dental plaque formed in the presence of sucrose would be more cariogenic due to porosity of its extracellular matrix, which contains polysaccharides. In this way, substrates easily diffuse through dental plaque reaching the tooth-plaque interface where they are fermented to acids, resulting in greater pH falls [Zero et al, 1992]. Nevertheless, this great cariogenicity of plaque formed in the presence of sucrose was demonstrated in bacterial cultures grown in media with and without this disaccharide and Zero et al [1992] proved with experimental plaque that there was a higher demineralization on enamel under a plaque rich in extracellular glucans (bacteria grown in media with sucrose) than in its absence.…”

Erosion Remineralization Efficacy of Gel-to-Foam Fluoride Toothpastes in situ: A Randomized Clinical Trial

“…Enamel specimens (5 × 5 × 3 mm) were prepared from bovine permanent teeth according to a previously reported method [Zero et al, 1992]. Briefly, blocks were cut from the teeth, polished, sonicated, and rinsed in deionized water.…”