Dicalcium Phosphate Dihydrate Crystals Research Articles

Effect of humic compounds and some organic acids added during dicalcium phosphate dihydrate crystal growth process

A constant composition method was used to investigate the influence of humic compounds and phytic, mellitic and citric acids on the crystal growth of dicalcium phosphate dihydrate (DCPD). The additives studied strongly inhibit the crystallization of DCPD. The inhibition effect can be attributed to an interaction between functional groups and calcium ions on the crystal surface.

Growth of octacalcium phosphate and dicalcium phosphate dihydrate crystals in silica gels

AbstractThe crystallization of octacalcium phosphate (OCP) and dicalcium phosphate dihydrate (DCPD) have been studied at ambient temperature in silica gel using double diffusion system. The first stage of evolution of the OCP spherulites as well as their growth have been observed by optical microscopy. The growth rate of the OCP spherulites under stable external conditions was constant. The formation of DCPD crystals has been observed in the last stages of experiments.

Effect of Small Amounts of Pyrophosphate on Orthophosphate Sorption by Calcium Carbonate and Calcareous Soils1

In calcareous soils, sorption of orthophosphate (OP) by CaCO3 in soils often results in the formation of water-insoluble calcium (Ca) phosphate compounds that may reduce the available phosphorus (P) levels in soils for plant uptake. There is a need to develop techniques that will reduce P precipitation from water-soluble P fertilizers, thereby improving their fertilizer use efficiencies by crops on calcareous soils. Addition of small amounts of sodium pyrophosphate (NaPP) to monocalcium phosphate (MCP) may inhibit the formation of dicalcium phosphate dihydrate (DCPD) in calcareous soils and hence enhance the fertilizer P efficiency. The purpose of this study was to investigate: (i) the mechanism of the inhibitory effect of pyrophosphate (PP), and (ii) factors influencing the effect. The inhibitory effect of PP on OP sorption by CaCO3 was studied using chemical-reagent CaCO3 and four calcareous soils from Egypt under the condition of either continuous shaking or incubation. In the CaCO3 system, the effect depended on the amount of CaCO3, OP concentration, and reaction time. The inhibitory effect increased as the P ratio of PP/OP increased from 1:100 to 1:25. Under the condition of continuous shaking, PP did not act as a crystal growth inhibitor for DCPD in the presence of excess CaCO3, but rather reacted with CaCO3 surface which retarded the formation of DCPD nuclei on the CaCO1 surface and hence temporarily retarded the sorption of OP. Some of the materials from the incubated MCP-CaCO3-H2O system and some related soil studies were examined with the scanning electron microscope (SEM) to observe the physical changes resulting from the inhibitory effect of PP on OP sorption. The major reaction products of MCP in the CaCO3 system or in the calcareous soils with or without NaPP were identified as DCPD. However, the DCPD crystals formed in the presence of NaPP were much smaller than those formed in the absence of NaPP. This suggests that PP appears to act as a crystal growth inhibitor for DCPD when DCPD precipitates as discrete crystals from solution rather than precipitating on the surface of CaCO3. The smaller crystal size of DCPD formed in the presence of NaPP also may explain why more water-soluble P was extracted from the DCPD in the soils treated with NaPP than without, even after the inhibitory effect had disappeared.

The Seeded Growth of Calcium Phosphates. The Kinetics of Growth of Dicalcium Phosphate Dihydrate on Enamel, Dentin, and Calculus

The kinetics of growth of calcium phosphates on synthetic hydroxyapatite (HAP), human enamel, whole dentin, and human calculus has been studied at 37 C at pH values from 4.97 to 5.10 held constant by the pH-stat addition of base. Following an initial induction period, dicalcium phosphate dihydrate (DCPD) crystallization takes place on the surface of these solids in all cases, even though the solutions are highly supersaturated with respect to HAP. The second order crystal growth kinetics are characteristic of the crystallization of DCPD on pure DCPD seed material. The ability of the substrate surfaces to nucleate DCPD falls in the order, synthetic HAP greater than enamel greater than calculus greater than dentin. Nucleation of DCPD, which is completed during the initial induction period, is very sensitive to small changes in pH, from 4.99 to 5.10.

The effect of stannous fluoride, sodium fluoride and stannous chloride on the crystallization of dicalcium phosphate dihydrate at constant pH

A kinetic study has been made of the crystal growth of dicalcium phosphate dihydrate (DCPD) seed crystals from supersaturated solution at constant pH. A pH value of 5.6 was chosen in order to be able to compare the results with a previous investigation in which the growing crystals were in contact with a supersaturated solution whose pH was allowed to vary during the growth experiments. The rate of crystallization has been found to follow an equation of the form — dN dt = kSN 2 , where N represents the number of moles/1 of solid to be precipitated before equilibrium is reached, k is the rate constant and S is proportional to the number of active growth sites. In contrast to the additive sodium fluoride, both stannous fluoride and stannous chloride are effective inhibitors of crystal growth. The degree of inhibition, expressed in terms of the relative values of the rate constant k, can be interpreted in terms of an adsorption process at the active crystal growth surface sites.

Chondrocalcinosis Articularis (Pseudogout Syndrome)

Clinical, roentgenographic, and synovial fluid findings in 43 patients with chondrocalcinosis articularis (pseudogout syndrome) are analyzed and compared to those in previous series. The age of the patients at time of diagnosis ranged from 41 to 83 years; 33 patients were 60 years or older at time of diagnosis. Large joints were most commonly involved. Acute, subacute, and chronic arthritis were noted; chronic low-grade arthralgias were common. Results of serum calcium and phosphorus determinations were normal. Crystals identifiable as calcium pyrophosphate dihydrate were noted in synovial fluid study; in one patient, dicalcium phosphate dihydrate crystals were identified as well. Degenerative joint disease and rheumatoid arthritis were frequent associated findings. Acute symptoms had varying responses to intra-articular corticosteroid, colchicine, indomethacin, or phenylbutazone administration. Aspirin relieved chronic low-grade arthralgias.

Kinetics of dissolution of dicalcium phosphate dihydrate crystals.

The dissolution of dicalcium phosphate dihydrate has been studied by following changes in the calcium, phosphate, and hydrogen ion concentrations when undersaturated solutions are inoculated with seed crystals of the salt. The rate of dissolution follows an equation of the first order with respect to concentration; this suggests a diffusion-controlled process and changes in the rate of stirring that have a considerable effect on the observed rate. Experiments have been made at 15, 25, and 37 C and the energy of activation corresponding to the dissolution process is 3.8 kcal mol-1.

Chronic synovitis as a manifestation of calcium crystal deposition disease.

AbstractA 67‐year‐old woman had an 8‐year history of chronic polyarthritis associated with extensive chondrocalcinosis. Synovial biopsy on two occasions showed crystalline material in the synovium, associated with chronic granulomatous reaction. Polarizing microscopy studies suggested the presence of both calcium pyrophosphate dihydrate and dicalcium phosphate dihydrate crystals. Electron diffraction studies were also consistent with the presence of a mixed crystal population. The chronic arthritis seen appears to be the result of chronic synovial inflammation induced by calcium crystal deposits.