A mechanism for incorporation of carbonate into apatite

Chickerur, N. S.; Tung, Ming S.; Brown, W. E.

doi:10.1007/bf02408521

Cited by 149 publications

(86 citation statements)

References 16 publications

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“…FTIR analysis of the same enamel samples showed a preferential B-type substitution and a high OH deficiency in enamel crystals at early developmental stages and, with tissue maturation, an increase in CO3 occupying the OH sites in the crystalline lattice. The observed structural features of the early enamel mineral-namely, the preferential B-type substitution, the highest content of acid phosphate, and the OH deficiency-are in accord with the postulated mechanism involving the participation of an OCP-like precursor (Chickerur et al, 1980;Siew et al, 1992). In the last column of Table 2 are also shown the solubility products of the corresponding enamel samples (unpublished data), which are calculated on the basis of the obtained stoichiometries.…”

Section: Carbonatoapatite As the Most Appropriate Prototype Of Biominsupporting

confidence: 62%

“…The latter mechanism is realized in supersaturated solutions, where precipitation of apatite crystals is favorable; these crystals usually have sizes and habits that are distinguishable from the features of the original OCP. Incorporation of most impurities (e.g., carbonate) into biomineral is believed to take place during the hydrolysis process (Chickerur et al, 1980;Tomazic et al, 199Q1).…”

Section: Ocp Hydrolysis and The Effects Of Fluoride On This Processmentioning

confidence: 99%

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The Effect of Fluoride On Apatite Structure and Growth

Aoba

1997

Critical Reviews in Oral Biology & Medicine

186

120

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Fluoride participates in many aspects of calcium phosphate formation in vivo and has enormous effects on the process and on the nature and properties of formed mineral. The most well-documented effect of fluoride is that this ion substitutes for a column hydroxyl in the apatite structure, giving rise to a reduction of crystal volume and a concomitant increase in structural stability. In the process of enamel mineralization during amelogenesis (a unique model for the cell-mediated formation of well-crystallized carbonatoapatite), free fluoride ions in the fluid phase are supposed to accelerate the hydrolysis of acidic precursor(s) and increase the driving force for the growth of apatitic mineral. Once fluoride is incorporated into the enamel mineral, the ion likely affects the subsequent mineralization process by reducing the solubility of the mineral and thereby modulating the ionic composition in the fluid surrounding the mineral, and enhancing the matrix protein-mineral interaction. But excess fluoride leads to anomalous enamel formation by retarding tissue maturation. It is worth noting that enameloid/enamel minerals found in vertebrate teeth have a wide range of CO3 and fluoride substitutions. In the evolutionary process from elasmobranch through teleost enameloid to mammalian enamel, the biosystems appear to develop regulatory functions for limiting the fluoridation of the formed mineral, but this development is accompanied by an increase of carbonate substitution or defects in the mineral. In research on the cariostatic effect of fluoride, considerable emphasis is placed on the roles of free fluoride ions (i.e., preventing the dissolution and accelerating the kinetics of remineralization) in the oral fluid bathing tooth mineral. Fluoride also has been used for the treatment of osteoporosis, but much still remains to be learned about maximizing the benefit and minimizing the risk of fluoride when used as a public health measure.

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Section: Carbonatoapatite As the Most Appropriate Prototype Of Biominsupporting

confidence: 62%

Section: Ocp Hydrolysis and The Effects Of Fluoride On This Processmentioning

confidence: 99%

The Effect of Fluoride On Apatite Structure and Growth

Aoba

1997

Critical Reviews in Oral Biology & Medicine

186

120

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“…The hydrolysis rate, as indicated by decreases in pH and aCa/ aP in tables 2, 4, and 5, depends on the CO, content in the atmosphere and decreases in the or- The solubility products uuder different initial solution compositions at 4, 6, 4.8, 23.5, and 37 'C are shown in tables [6][7][8][9][10][11] together with the equilibrium times, composition of solutions and ACa/ AP. The results indicate that hydrolysis is slower when the initial solution has lower pH (i.e., higher phosphoric acid concentration), lower temperature, or the initial solution is supersaturated.…”

Section: Resultsmentioning

confidence: 99%

Octacalcium Phosphate Solubility Product from 4 to 37-Degree-C

Tung¹,

Eidelman²,

Sieck³

et al. 1988

J. RES. NATL. BUR. STAN.

117

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Octacalcium phosphate (OCP) is proving to be an important intermediary in the formation of tooth and bone mineral and various pathological calcifications. Before this mineral can form, its solubility product must be exceeded. Thus, a knowledge of its precise values under various conditions is required for a basic understanding of calcification processes. The methodology suitable for measuring the solubility of metastable phases was developed and used to determine the negative logarithms of the solubility products of OCP, p K sp (OCP), at 4, 4.8, 6, 18, 23.5, and 37 °C. This methodology includes (1) the use of high solid-to-liquid ratio, 10 mg/mL, to minimize the effects of hydrolysis, (2) frequent sampling during equilibration to detect possible effects of hydrolysis, (3) equilibration from supersaturation and from undersaturation, and (4) equilibration in the absence and presence of a CO 2 -containing atmosphere. The resulting p K sp (OCP) values are 48.3±0.2, 48.3±0.2, 48.2, 48.3, 48.4±0.1 and 48.7±0.2 at 4, 4.8, 6, 18, 23.5, and 37 °C. A 5.5% CO 2 atmosphere did not change the apparent p K sp (OCP) value significantly. The value of p K sp (OCP) obtained by approaching equilibrium from supersaturation was essentially the same as that from undersaturation. The effects of (1) the use of different ionic models, (2) OCP hydrolysis, and (3) differences in equilibrium constants on the apparent p K sp (OCP) values are described; the latter two contribute significantly to the differences in p K sp (OCP).

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“…These ions seem to have little effect on the crystallinity of CO, apatites. However, in general they greatly affect the crystallographic structure of the apatite during its formation process [LeGe ros, 1977;Chickerur et al, 1980], In spite of its good crystallinity and the existence of many H C03~ ions in the solu tion, it should be noted here that the crystal linity of well-crystallized 80-CO3Ap con taining a carbonate content of 6.4 wt%> in creased when compared with the original apatite, probably because of the high car bonate content. Therefore, we can conclude that COj apatites tend to repair themselves in solution, even if there is a high concen tration of H C 03~ ions.…”

Section: I)mentioning

confidence: 99%

Crystallinity Changes of CO₃-Apatites in Solutions at Physiological pH

Okazaki¹,

Moriwaki²,

Aoba

et al. 1982

Caries Res

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To study the chemical stability of carbonate-containing apatites in solutions with near-neutral pH, synthetic CO₃ apatites with various carbonate contents were prepared at 60 and 80 °C. The crystallinity of CO₃ apatites was adopted as an indicator of their chemical stability. Incubation for 1 month in distilled water decreased the carbonate content of CO₃ apatites synthesized at 60 °C, and greatly increased the crystallinity along the c axis. In metastable solutions containing Ca²⁺, HPO₄^2-, and HCO₃^- ions at physiological pH, the crystallinity along the c axis increased without interference from those ions. These results indicate that CO₃, apatites tend to change to more stable apatites with higher crystallinity and lower carbonate content, even in the presence of a high concentration of HCO₃^- ions.

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A mechanism for incorporation of carbonate into apatite

Cited by 149 publications

References 16 publications

The Effect of Fluoride On Apatite Structure and Growth

The Effect of Fluoride On Apatite Structure and Growth

Octacalcium Phosphate Solubility Product from 4 to 37-Degree-C

Crystallinity Changes of CO₃-Apatites in Solutions at Physiological pH

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A mechanism for incorporation of carbonate into apatite

Cited by 149 publications

References 16 publications

The Effect of Fluoride On Apatite Structure and Growth

The Effect of Fluoride On Apatite Structure and Growth

Octacalcium Phosphate Solubility Product from 4 to 37-Degree-C

Crystallinity Changes of CO3-Apatites in Solutions at Physiological pH

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About

Crystallinity Changes of CO₃-Apatites in Solutions at Physiological pH