An intermediate state in hydrolysis of amorphous calcium phosphate

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

doi:10.1007/bf02405124

Cited by 98 publications

(59 citation statements)

References 26 publications

(48 reference statements)

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“…LDSAED from plates aged for 1 month revealed a peak at d ¼ 0.28 nm corresponding to the (211)/(112) planes of AP (Fig. 3a), implicating that, as in previous reports 23,24,[28][29][30][31] , the OCP-like structure acted as a precursor for AP. These structural developments were supported by in situ Fourier transform infrared spectroscopy (FTIR, Fig.…”

Section: Resultssupporting

confidence: 82%

Ion-association complexes unite classical and non-classical theories for the biomimetic nucleation of calcium phosphate

et al. 2013

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Despite its importance in many industrial, geological and biological processes, the mechanism of crystallization from supersaturated solutions remains a matter of debate. Recent discoveries show that in many solution systems nanometre-sized structural units are already present before nucleation. Still little is known about the structure and role of these so-called pre-nucleation clusters. Here we present a combination of in situ investigations, which show that for the crystallization of calcium phosphate these nanometre-sized units are in fact calcium triphosphate complexes. Under conditions in which apatite forms from an amorphous calcium phosphate precursor, these complexes aggregate and take up an extra calcium ion to form amorphous calcium phosphate, which is a fractal of Ca 2 (HPO 4 ) 3 2 À clusters. The calcium triphosphate complex also forms the basis of the crystal structure of octacalcium phosphate and apatite. Finally, we demonstrate how the existence of these complexes lowers the energy barrier to nucleation and unites classical and non-classical nucleation theories.

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Section: Resultssupporting

confidence: 82%

Ion-association complexes unite classical and non-classical theories for the biomimetic nucleation of calcium phosphate

et al. 2013

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“…In fact, it is well-documented that amorphous tricalcium phosphate (ACP) is the first solid to be spontaneously precipitated in highly supersaturated solutions. This amorphous phase is unstable under physiological temperature and pH conditions (Meyer and Eanes, 1978), so that ACP readily converts, by an autocatalytic solution-mediated crystallization process (Eanes and Meyer, 1978), to intermediate phases such as DCPD or OCP (Tung and Brown, 1983). These acidic intermediate phases are also not stable but can further hydrolyze to apatite crystals under physiological conditions.…”

Section: Driving Force For Precipitation Of Calcium Phosphatesmentioning

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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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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“…In supersaturated calcifying solutions, calcium deficient HA (Cain _ HX(PO4)6 (OH)2_X, 0<_ x <_2 ; Ca-deficient HA) (Winand 1965) has been shown to precipitate via the formation of one or more precursors such as amorphous calcium phosphate (Ca3(P04)2.nH2O ; ACP) (Eanes and Meyer 1977;Meyer and Eanes 1978a, b ;Tung and Brown 1983). For that reason, it is believed that precursor phases such as ACP, dicalcium phosphate dihydrate (CaHPO4.2H2O ; DCPD) and octacalcium phosphate (Ca8H2(P04)6.5H2O ; OCP) may participate in biological mineralization (Nancollas et al 1989).…”

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confidence: 99%

Bone Formation on Synthetic Precursors of Hydroxyapatite.

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Nakamura

Miyasaka

et al. 1991

Tohoku J. Exp. Med.

261

312

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The aim of this study was to investigate the reaction of skeletal tissue to various synthetic calcium phosphate (Ca-P) compounds in vivo. Five synthetic Ca-P compounds were implanted into the subperiosteal area of the calvaria of 7-week-old BALB/c mice for one to 15 weeks. Synthetic compounds were dicalcium phosphate (DCP), octacalcium phosphate (OCP), amorphous calcium phosphate (ACP), Ca-deficient hydroxyapatile and hydroxyapatile (HA). Implanted DCP, OCP and ACP were found to be converted to apatitic phase by x-ray microdiffraction analysis using undecalcified specimens. Structure of bone was found out on all of Ca-P compounds eventually at late stage under the light microscope, but the rate of bone formation calculated from a number of experiments varied on respective synthetic Ca-P compound. It was high as 80% for DCP, OCP and ACP, but was low as 5.6% for Ca-deficient HA, and no reaction was found for HA at the stage of 3 weeks. Fine filaments and granular materials in the newly formed bone matrix were detected at 7 days around the remnants of OCP particles which already converted to apatitic phase by ultrastructural study of decalcified specimens. These structures were very similar to the components of bone nodules seen in intramembranous osteogenesis. It is postulated that the precursors of HA have an important role in intramembranous osteogenesis.calcium phosphate (Ca-P) compounds ; precursors ; hydroxyapatile ; bone formation ; bone matrix

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An intermediate state in hydrolysis of amorphous calcium phosphate

Cited by 98 publications

References 26 publications

Ion-association complexes unite classical and non-classical theories for the biomimetic nucleation of calcium phosphate

Ion-association complexes unite classical and non-classical theories for the biomimetic nucleation of calcium phosphate

The Effect of Fluoride On Apatite Structure and Growth

Bone Formation on Synthetic Precursors of Hydroxyapatite.

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