ISSN:
1432-0827
Schlagwort(e):
Amelogenesis
;
Enamel mineral
;
Carbonatoapatite
;
Solubility
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
,
Medizin
,
Physik
Notizen:
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.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00296292
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