The influence of fluoride on in vitro remineralization of bovine enamel

Remineralization experiments using bovine enamel were carried out with 2 ppm fluoride or no fluoride added to the remineralizing solutions.The group without fluoride showed (quantitative microradiography) significantly more remineralization in the first 50 µm of the lesion than the fluoride group.It is suggested that fluoride may inhibit remineralization.Une expérimentation portant sur la reminéralisation de l’émail a été menée sur de l’émail bovin, en utilisant des solutions de reminéralisation sans adjonction de fluorure et avec adjonction de 2 ppm de fluorure.La microradiographie quantitative a montré, dans le groupe sans fluorure, une reminéralisation plus importante, dans les premiers 50 µm de la lésion, que dans le groupe avec fluorure.Ces résultats suggèrent que les fluorures puissent inhiber la reminéralisation

Variations in the mineral composition of human enamel on the level of cross-striations and striae of Retzius

Point count analyses were made with the electron microprobe for Ca, Na and Mg in a vertical cross-section through the enamel of a freshly erupted human pre-molar in the approximal area. A low excitation energy was chosen to limit the size of the excited volume and to suppress the evaporation of Na. The Na content showed variations with a wavelength of 6 ± 1 µm, which equals the distance of cross-striations. The Mg content showed variations with a wavelength of 25 ± 4 µm which equals the distance of striae of Retzius, whereby these striae probably contain a higher Mg content. On the assumption that higher Na and/or Mg contents represent mineral with a higher solubility, the observed variations in mineral composition help to explain the fine structure of carious lesions as observed frequently by microscopy and microradiography

Electron microprobe and microradiographic studies of carious enamel lesions covered with dental calculus

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Microradiography and electron microprobe analysis of some natural white and brown spot enamel lesions with and without laminations

Extensive ‘white spot’ and ‘brown/white spot’ lesions with intact surfaces in 11 molars were investigated by microradiography and electron microprobe analysis for Fe, Ca, Na and Cl. At the surface of the brown spots some Fe was found. Within the lesions a preferential dissolution of Na and a slight enrichment of Cl was found. This suggests that Na and Cl are sited in different parts of the mineral and the Na-containing part appears to be more soluble. The Na and Cl contents of a lamination approach those of adjacent sound enamel. This indicates that laminations do not result from major reprecipitation of a less soluble calcium phosphate within the formed lesion, but that the mineral is protected from local dissolution early in the process. A possible mechanism is discussed

Electron microprobe analysis and microradiography of some artificial laminated carious lesions

Artificial laminated carious lesions were made on the buccal surface of human premolars. The volume percentage of mineral was determined as a function of depth by microradiography. Using the electron microprobe, the signals for Ca, Na, Mg, P and Cl were recorded as a function of depth both through the lesions and through the adjacent sound enamel. In the demineralized parts of the lesions there was a preferential loss of Na and a preferential retention of Cl. In the surface layers and the laminations the Na/Ca and Cl/Ca ratios were practically the same as in the adjacent sound enamel. This indicates that these surface layers and laminations were not formed by gross dissolution of the original mineral followed by gross precipitation of another, less soluble calcium phosphate, but that they remained there during the continuous demineralization due to the fact that the microcrystals became resistant to dissolution, perhaps due to protection by a thin layer of precipitated fluorapatite or fluoridated hydroxyapatite. In a previous study the same was found for surface layers and laminations in natural laminated carious lesions. This indicates that during continuous in vitro demineralization tooth enamel mineral behaves similarly as during intermittent in vivo demineralization

Posteruptive maturation of tooth enamel studied with the electron microprobe

Third molars just erupting and premolars (before eruption or half a year or 3.5 years after eruption) were extracted and sawn vertically through the buccolingual plane. Tracings of the Ca, P, Na and Mg contents of the outer 100-µm layer of the enamel were made with an electron microprobe. Care was taken to limit the diameter of the excited volume to about 1 µm and to suppress the evaporation of Na. On the unerupted and freshly erupted surfaces the Na and Mg content varied from 50 to 80% of the content at 100 µm depth. However, half a year or 3.5 years after eruption the Na and Mg contents were negligibly small at the tooth surface and they remained smaller than in unerupted or freshly erupted teeth up to a depth of 10–30 µm. These data suggest that posteruptive maturation occurs in the mineral of the outer layer of tooth enamel whereby it builds up a higher resistance to carious breakdown. This interpretation is corroborated by clinical findings reported in the literature. The consequences of wear and abrasion on these phenomena are not known yet. The above-mentioned depth of 10–30 µm agrees with the penetration depth of pH changes estimated to result from the consumption of foods and drinks with varying pH