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  • Biomineralization  (1)
  • Carbonatoapatite  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Epitaxial overgrowth of apatite crystals on the thin-ribbon precursor at early stages of porcine enamel mineralization (1993)
    Springer
    Calcified tissue international 53 (1993), S. 249-256 
    Details
    ISSN: 1432-0827
    Keywords: Enamel ; Amelogenesis ; Crystal growth ; Calcium phosphates ; Biomineralization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The aim of the present work was to investigate changes in cross-sectional morphologies of enamel crystallites as a function of location in secretory porcine enamel. Enamel tissues were obtained from 5- to 6-month-old slaughtered piglets. For examination by electron microscopy, a portion of the secretory enamel was embedded in resin and ultrathin sections were prepared with a diamond knife. In parallel studies, compositional and structural changes of enamel mineral were assessed by chemical analysis and Fourier transform infrared (FTIR) spectroscopy. For this purpose, two consecutive layers of the outer secretory enamel, each approximately 30 μm thick, were separated from the labial side of permanent incisors. Using high-resolution electron microscopy, early events of enamel crystal growth were characterized as the epitaxial growth of small apatite units on the lateral surfaces of the initially precipitated thin ribbon. These apatite units had regular triangle or trapezoid cross-sections. After fusions of those isolated trapezoids on both lateral sides of the platy template, the resulting enamel crystallites had the well-documented flattened-hexagonal shapes in cross-sections. The initially precipitated thin plate was buried inside the overgrown apatite lamella and then retained as a central dark line. Similar morphological evidence for the epitaxial nucleation and overgrowth of carbonatoapatite on the platy template was obtainedin vitro. Chemical and FTIR analyses of the enamel layer samples showed that the characteristics of the youngest enamel mineral were distinct from those of enamel crystals found in older secretory enamel. The overall results support the concept that initial enamel mineralization comprises two events: the initial precipitation of thin ribbons and the subsequent epitaxial growth of apatite crystals on the two-dimensional octacalcium phosphate-like precursor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01320910
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Changes in the solubility of enamel mineral at various stages of porcine amelogenesis (1992)
    Springer
    Calcified tissue international 50 (1992), S. 266-272 
    Details
    ISSN: 1432-0827
    Keywords: Amelogenesis ; Enamel mineral ; Carbonatoapatite ; Solubility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The solubility of enamel mineral (a carbonated apatite) formed at various stages of porcine amelogensis was investigated at controlled partial pressures of CO2. Enamel samples were obtained from the outer (young) secretory, inner (old) secretory, early (soft) and late (hard) mature enamel of the permanent dentition of slaughtered piglets. The dissected enamel was pulverized and subjected to a plasma ashing at low temperature to remove organic matter. The composition (Ca, total P, HPO4, and CO3) of the enamel mineral was determined chemically. The enamel mineral contained significant amounts of carbonate and acid phosphate: the model adopted for its stochiometry was [Ca]5-x [HPO4]v[CO3]w[PO4]3-x[OH]1-x. Each enamel sample was equilibrated in dilute phosphoric acid solutions (0.01–1.2 mM) under Pco2=1.86 and 1.75%. Equilibration of the enamel samples usually took 20–25 days; the solution composition (pH, concentrations of Ca, P, Mg, Na, and K, and activity of Ca2+) was determined periodically. The composition of the solution at equilibrium showed that (1) the outer (younger) secretory mineral was the most soluble and the solubility of enamel mineral decreased with advancing developmental stages; (2) the mean activity product in the saturated solutions for the outer secretory enamel was the same as that calculated on the basis of the reported composition of the enamel fluid; and (3) the solubility data obtained with most of the enamel samples were consistent with a model in which the equlibration includes two processes: dissolution of the original enamel mineral and precipitation of a new carbonatoapatite. Analyses of the equilibrated samples, particularly the mature enamel, by electron microscopy, supported the precipitation of carbonatoapatite. The overall results are in good agreement with previous results indicating that significant changes in the composition and structure of porcine enamel mineral occur with the mineralization progress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296292
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    Paper (German National Licenses)
    Fulltext
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