title: Effect of a diffusion layer on the nature of enamel demineralization.
abstract: The aim of the present study was to evaluate the significance of diffusion barriers in the development of artificial caries-like lesions. A 30-mm2 enamel surface area was covered with a layer of filter paper and exposed to a gently agitated 50 mM acetate buffer, pH 4.5, containing either 0.1 or 1.0 ppm fluoride for up to 48 h at 20 degrees C. Similar enamel surfaces, but unprotected by filter paper, served as controls. It was found that below the filter paper an approximately 60-microns-deep caries-like lesion was developed exhibiting a preserved surface layer, the mineral content of which depended on the fluoride concentration of the buffer. The lesions of the control teeth without a filter paper coverage were erosion-like surface lesions. In the filter paper calcium and phosphate released from the enamel combined with fluoride from the bulk solution had established a supersaturation with respect to fluorapatite while the undersaturation with respect to hydroxyapatite was maintained, which caused a caries lesion to develop. The lesions produced in noncovered enamel by bulk solution unsaturated with respect to both apatites were erosion-like. It was concluded that a diffusion barrier can significantly favor the establishment of supersaturation with respect to fluorapatite and thus facilitate the development of a subsurface caries-like lesion at the expense of the erosion.
authors.affiliation: Department of Oral Anatomy, Dental Pathology and Operative Dentistry, Royal Dental College, Aarhus, Denmark.
authors.forename: M J
authors.initials: MJ
authors.lastname: Larsen
mesh_terms: D001031:Apatites / Q000032:analysis / Q000378:metabolism; D002118:Calcium / Q000032:analysis / Q000493:pharmacokinetics; D003731:Dental Caries / Q000378:metabolism* / Q000473:pathology; D003743:Dental Enamel / Q000378:metabolism* / Q000473:pathology; D004058:Diffusion; D017886:Durapatite; D005374:Filtration / Q000295:instrumentation; D005459:Fluorides / Q000032:analysis / Q000493:pharmacokinetics*; D006801:Humans; D006882:Hydroxyapatites / Q000032:analysis / Q000378:metabolism; D008954:Models, Biological; D010209:Paper; D010710:Phosphates / Q000032:analysis / Q000493:pharmacokinetics; D012995:Solubility; D014077:Tooth Erosion / Q000378:metabolism / Q000473:pathology
chemical_list: D001031:Apatites; D006882:Hydroxyapatites; D010710:Phosphates; D017886:Durapatite; C025105:fluorapatite; D005459:Fluorides; D002118:Calcium