X-ray diffraction of enamel of a freshly erupted human tooth

No abstract availabl

X-ray diffraction of enamel of a freshly erupted human tooth

No abstract availabl

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

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

X-ray diffraction of enamel of a freshly erupted human tooth

No abstract availabl