The structure and composition of some calcium-deficient apatites

Berry, E.E.

doi:10.1016/0022-1902(67)80033-2

Cited by 201 publications

(98 citation statements)

References 13 publications

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“…In addition to PO43-ions, however, HFO4 groups are present in the hydroxyapatite [Berry, 1967]. Exchange of these acid phosphate groups for FPO3 would cause no such imbalance.…”

Section: Nature O F Exchanging Speciesmentioning

confidence: 99%

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The Reaction of Monofluorophosphate with Apatite

Ingram¹

1972

Caries Res

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The action of sodium monofluorophosphate on Syntheti chydroxyapatites has been studied using pure mono- syntheticfluorophosphate solutions.Monofluorophosphate-treated hydroxyapatite was less soluble in acid buffer than fluoride-treated mineral of similar fluorine content. During the reaction some orthophosphate was liberated from the solid and addition of orthophosphate to the monofluorophosphate inhibited subsequent uptake of fluorine by the hydroxyapatite. The FPO₃ anion was present in the treated hydroxyapatite and was shown to have replaced the hydrogen phosphate group of the calcium-deficient hydroxyapatites. In this way the capacity of a calcium-deficient hydroxyapatite for uptake of monofluorophosphate was related to its HPO₄ content; i.e. its Ca:P molar ratio. Replacement of the acid phosphate groups of the hydroxyapatite, either by FPO₃ substitution or by thermal condensation to pyrophosphate reduced the isotopic exchange of orthophosphate by the mineral.

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“…In addition to PO43-ions, however, HFO4 groups are present in the hydroxyapatite [Berry, 1967]. Exchange of these acid phosphate groups for FPO3 would cause no such imbalance.…”

Section: Nature O F Exchanging Speciesmentioning

confidence: 99%

“…They were calcium phosphates within the compositional range of Ca id-x(H P 04)x(P 0 4V-x(0 H )2-xxH 20 i.e. those calcium phosphates with a molar C a: P ratio o f 1.50-1.67 as describ ed by Berry [1967] using infrared and DTA methods, following the work of Winand and D allemagne [1962].…”

mentioning

confidence: 99%

The Reaction of Monofluorophosphate with Apatite

Ingram¹

1972

Caries Res

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“…conflicting views, two models involving ionic defects have been proposed without recourse to the presence of octacalcium phosphate, a phosphate of low calcium content (3)(4)(5). In support of these models, which may be represented by the formulae l,Calo -,(HP04)X(Po4)6 -,(OH), -, and 2, Cal 0 -x(HP04)x(P04)6 -.…”

Section: Introductionmentioning

confidence: 99%

The Fluoridation of Nonstoichiometric Calcium Hydroxyapatite. An Infrared Study

Amberg¹,

Luk²,

Wagstaff³

1974

Can. J. Chem.

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Calcium deficient hydroxyapatites were impregnated to varying degrees with fluoride in very dilute solutions of NaF at room temperature. Ca/P ratios were determined before and after fluoridation. Phosphate loss upon fluoridation was consistent with an initial mechanism of OH− vacancy filling by F−, with equivalent amounts of PO43− ions escaping to restore charge balance. Infrared measurements confirmed previous evidence of OH/F exchange and the formation of [Formula: see text] hydrogen bonds, which increased with progressive thermal activation, considerable exchange having occurred already at 120 °C and possibly below. The first signs of lattice collapse occurred near 600 °C, with the fluorided sample exhibiting somewhat better stability.

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“…A, by planar CO32-ions, with a C -0 distance, in calcite, of 1.29 A [Wells, 1962], As dental mineral is a calcium-deficient apatite, a synthetic hydroxy apatite within the range: Ca,o-x(HPO4)x(PO.,)0 -x(OH)2 -xxH>0, where 0 < X < 1 [Berry, 1967], that is, with a Ca:P molar ratio o f 1.50 -1.67, was chosen as a model.…”

Section: The Role O F Carbonate In Dental Mineralmentioning

confidence: 99%

The Role of Carbonate in Dental Mineral

Ingram¹

1973

Caries Res

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The mechanism by which calcium-deficient hydroxyapatite can become carbonate apatite has been investigated by means of a monofluorophosphate competition experiment, measurement of phosphate exchange and uptake of ¹⁴C-labelled bicarbonate in the presence of various concentrations of orthophosphate. It was found that acid phosphate groups were displaced from the crystal surface by treatment with bicarbonate. This did not result in a greater acid solubility of the mineral. Moreover, removal or replacement of the acid phosphate groups from the crystals prevented them from acting as nucleators or centres of crystal growth in a calcifying medium. Therefore, when dental mineral is formed in the presence of bicarbonate, some of the acid phosphate groups are displaced, limiting the growth of the crystals. This results in a proportion of small crystals being present having a high CO₂ content and being readily dissolved during carious or acid attack. This accounts for the observed inhibition of calcification by bicarbonate and for the preferential loss of CO₂ during caries.

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The structure and composition of some calcium-deficient apatites

Cited by 201 publications

References 13 publications

The Reaction of Monofluorophosphate with Apatite

The Reaction of Monofluorophosphate with Apatite

The Fluoridation of Nonstoichiometric Calcium Hydroxyapatite. An Infrared Study

The Role of Carbonate in Dental Mineral

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