The Formation and Influence of Surface Phases on Calcium Phosphate Solids

Francis, Marion D.; Gray, J. A. B.; Griebstein, W.J.

doi:10.1016/b978-1-4832-3119-8.50010-x

Cited by 50 publications

(8 citation statements)

References 27 publications

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“…lution can cause spherical CaF 2 precipitates on enamel surfaces. Such CaF 2 precipitation was thought to promote fluoride release and remineralization of enamel hydroxyapatite [Francis et al, 1968;Caslavska et al, 1975]. Our results, however, show that under controlled conditions fluoride can be incorporated directly into fluoridated hydroxyapatite grown on an etched enamel surface without the formation of spherical CaF 2 particles.…”

Section: Discussioncontrasting

confidence: 39%

Effect of Fluoride on the Morphology of Calcium Phosphate Crystals Grown on Acid-Etched Human Enamel

2009

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The aim of this study was to examine the effect of fluoride ion concentration on the morphology of calcium phosphate crystals grown on acid-etched enamel as a model for tooth enamel erosion. Samples were immersed in calcification solution for 16 h and changes in crystal morphology were monitored by field emission scanning electron microscopy. Without fluoride, plate-like octacalcium phosphate crystals (20 nm thick, 2–10 μm wide) were formed. With 1–10 mg/l fluoride, arrays of denser needle-like nanocrystals (20–30 nm wide, >500 nm in length) were formed. We conclude that there is a minimal fluoride concentration (1 mg/l) that dramatically affects the morphology of calcium phosphate crystals grown on etched enamel in vitro.

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Section: Discussioncontrasting

confidence: 39%

Effect of Fluoride on the Morphology of Calcium Phosphate Crystals Grown on Acid-Etched Human Enamel

2009

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“…The HAp compositions produced at low temperature can be expressed as: Ca 10-x (HPO 4 ) x (PO 4 ) 6-x (OH) 2-x where x ranges from 0 to 1. The two terminal compositions are, therefore, Ca 10 (PO 4 ) 6 (OH) 2 for stoichiometric HAp, and Ca 9 (HPO 4 )(PO 4 ) 5 OH for fully calcium-deficient HAp. Thus, stoichiometric HAp has a calcium-to-phosphate (Ca/P) ratio of 1.67 and Ca 9 (HPO 4 )(PO 4 ) 5 OH has a Ca/P ratio of 1.5.…”

Section: Introductionmentioning

confidence: 99%

“…It is well documented that CaF 2 forms when HAp is exposed to high fluoride concentrations in solution. [9][10][11][12] McCann, 9 in particular, observed CaF 2 after exposing apatites having various Ca/P ratios to different concentrations of NaF, then measuring the solid and liquid compositions to determine the amount of CaF 2 and fluorapatite formed. An elevated concentration of phosphate in solution was taken as evidence of CaF 2 formation while the absence of phosphate presumed fluorapatite formation.…”

Section: Introductionmentioning

confidence: 99%

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Fluoride uptake by hydroxyapatite formed by the hydrolysis of ?-tricalcium phosphate

Leamy

Brown

TenHuisen

et al. 1998

J. Biomed. Mater. Res.

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Although there is interest in forming synthetic analogs of hard tissues at physiologic temperature, significant gaps in knowledge exist with respect to the mechanisms by which precursor solids convert to apatites and also with respect to the apatite compositions that may be formed. In this study calcium-deficient HAp [Ca9(HPO4)(PO4)5OH] was prepared by hydrolysis of tricalcium phosphate (TCP), alpha-Ca3(PO4)2. The kinetics of HAp formation were studied as a function of temperature by isothermal calorimetry. TCP hydrolyzed completely within about 12 h, and the hydrolysis reaction evolved 133 kJ/mol of HAp formed. Although the kinetics of hydrolysis exhibited a strong temperature dependence, the mechanistic path taken appeared independent of temperature. The fluoridation of hydroxyapatite compositions having Ca/P ratios higher than 1.59 previously has been investigated. However, little work has been done on the fluoridation of more calcium-deficient hydroxyapatite. Ca9(HPO4)(PO4)5OH was formed at temperatures between 37.4 degrees and 55 degrees C to vary its morphology. These preparations then were reacted in NaF solution and the kinetics of fluoride incorporation studied. Solution chemical analyses were used to determine the amounts of fluoride incorporated. The extent of hydroxyl replacement by fluoride ranged from 17 to 72% and correlated with the surface area of the parent HAp.

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“…Overall, the solution chemical approaches provide compositional information, but the existence of specific phases must be generally inferred indirectly. Although the spectroscopic (XPS, IR, and so forth) and diffraction (X-ray powder diffraction, including grazing techniques) methods are capable of identifying bulk phases, they are in certain instances limited by the thinness of the films of reacted fluoride on the mineral surfaces and by the similarity of the fluoride chemical environment in fluorapatite and fluorohydroxyapatite (13,(36)(37)(38)(39)(40)(41)(42).…”

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confidence: 99%

¹⁹F MAS-NMR and solution chemical characterization of the reactions of fluoride with hydroxyapatite and powdered enamel

et al. 1988

Acta Odontologica Scandinavica

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Solution chemical and 19F magic angle spinning-nuclear magnetic resonance (MAS-NMR) methods have been utilized to study the effects of fluoride dose, fluoridating pH, and mineral surface area on the dynamics of fluoride reactivity with hydroxyapatite and powdered human dental enamel in vitro. Both solution chemical fluoride uptake and NMR measurements demonstrated that the reaction products of ionic fluoride with apatite include mixtures of FAP, FHAP, and CaF2, with increased amounts of CaF2 promoted by increased F concentration or decreased pH. NMR analysis showed FAP or FHAP as a reaction product of fluoride uptake under all conditions, regardless of whether CaF2 was formed, unambiguously demonstrating fluorite as an additive rather than substitute form of F reactivity. pH stat measurements demonstrated the release of OH- during F reactivity with apatites corresponding to ion exchange formation of FAP/FHAP or dissolution/reprecipitation formation of CaF2. Phosphate release into solution accompanied fluoride uptake under all conditions, including regions where ion exchange predominated. Whereas powdered dental enamel demonstrated fluoride uptake behavior similar to that of synthetic apatite, the resulting reaction products differed as analyzed by 19F MAS-NMR.

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The Formation and Influence of Surface Phases on Calcium Phosphate Solids

Cited by 50 publications

References 27 publications

Effect of Fluoride on the Morphology of Calcium Phosphate Crystals Grown on Acid-Etched Human Enamel

Effect of Fluoride on the Morphology of Calcium Phosphate Crystals Grown on Acid-Etched Human Enamel

Fluoride uptake by hydroxyapatite formed by the hydrolysis of ?-tricalcium phosphate

¹⁹F MAS-NMR and solution chemical characterization of the reactions of fluoride with hydroxyapatite and powdered enamel

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The Formation and Influence of Surface Phases on Calcium Phosphate Solids

Cited by 50 publications

References 27 publications

Effect of Fluoride on the Morphology of Calcium Phosphate Crystals Grown on Acid-Etched Human Enamel

Effect of Fluoride on the Morphology of Calcium Phosphate Crystals Grown on Acid-Etched Human Enamel

Fluoride uptake by hydroxyapatite formed by the hydrolysis of ?-tricalcium phosphate

19F MAS-NMR and solution chemical characterization of the reactions of fluoride with hydroxyapatite and powdered enamel

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¹⁹F MAS-NMR and solution chemical characterization of the reactions of fluoride with hydroxyapatite and powdered enamel