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Biomedical subjects

J D Featherstone

Publications and source records attributed to J D Featherstone.

At least 91 records · Page 5Linked to original sources
PubMed1983

Synthetic apatites containing Na, Mg, and CO3 and their comparison with tooth enamel mineral.

Apatites containing Na, Mg, and CO3 in amounts occurring in tooth enamel mineral were synthesized by precipitation from aqueous solutions. The X-ray diffraction patterns showed only apatitic reflections, which were somewhat broader than those of enamel. X-ray Guinier photographs resulted in diffuse reflections from which the lattice parameters could not be determined. The infrared (IR) absorption spectrum of the synthetic samples was practically identical with that of tooth enamel. However, after heating the samples for 1/2 h at a temperature between 300 and 600 degrees C, no absorption peak was found at 2340 cm-1 as in the IR spectrum of tooth enamel after heating.

Apatites↗
PubMed1983

Acid reactivity of carbonated apatites with strontium and fluoride substitutions.

Carbonated apatites containing approximately 3.0 or 6.5% CO3 were precipitated in the presence of sodium, strontium, and/or fluoride at various concentrations. Almost all the available strontium and fluoride was incorporated into the crystals, whereas only a portion of the carbonate and sodium present was taken up. When incorporated together, Sr and F improved the crystallinity of carbonated apatites and markedly reduced their acid reactivity. This phenomenon may partially explain the observed reduction in caries for populations whose drinking water contains optimum levels of Sr at 5-10 mg/l and F at 1-2 mg/l.

Apatites↗
PubMed1982

Paracrystalline disorder of biological and synthetic carbonate-substituted apatites.

Paracrystalline disorder, a type of lattice imperfection which results in a loss of long-range crystalline order, was assessed in a range of biological and synthetic apatites using x-ray diffraction data. Carbonate substitution in the apatite lattice increased the amount of paracrystalline disorder in synthetic precipitated apatites, whereas trace amounts of fluoride and, to a lesser extent, zinc and strontium partially offset the disorder induced by carbonate. Paracrystalline disorder was significantly reduced in synthetic apatites prepared by high-temperature solid-state reaction. Human dental enamel was less disordered than either dentin or bone.

Apatites↗
PubMed1982

Preparation, analysis, and characterization of carbonated apatites.

A range of synthetic carbonated apatites were characterized using infrared and Raman spectroscopy, X-ray diffraction, and chemical analysis and compared to stoichiometric hydroxyapatite and dental enamel. Synthetic apatites were prepared by aqueous precipitation and by solid-state reaction at high temperatures. A method is described for the carbonate determination of apatite samples using gas chromatography. This study demonstrates that carbonate exists in two crystallographically distinct sites in the apatite crystal structure and is consistent with a carbonate-for-phosphate substitution mechanism, where four carbonate groups replace three phosphate groups. Sodium and hydroxyl ions are shown to be involved with the substitution of carbonate ions in the apatite structure. Observed sodium/carbonate and calcium/phosphorus molar ratios confirm this mechanism. Substitution of this type may explain the predominant mode of carbonate substitution in biological apatites.

Apatites↗