�� In ��-TCP, there are three types of crystallographically nonequivalent PO43- groups located at general points of the crystal, each type MG132 msds with different intratetrahedral bond lengths and angles. At temperatures above ~1,125��C, ��-TCP is transformed into a high-temperature phase ��-TCP. Being the stable phase at room temperature, ��-TCP is less soluble in water than ��-TCP (Table 1). Furthermore, the ideal ��-TCP structure contains calcium ion vacancies that are too small to accommodate calcium ions but allow for the inclusion of magnesium ions, which thereby stabilize the structures.204,205 Both ion-substituted206-209 and organically modified210-212 forms of ��-TCP can be synthesized as well. The maximum substitution of Mg2+ in ��-TCP was found to correspond to the Ca2.61[Mg(1)0.28,Mg(2)0.
11](PO4)2 stoichiometric equation.209 The modern structural data on ��-TCP are available in references 213�C215; those on Vicker��s and Knoop microhardness studies might be found if reference 216, while solubility data can be found in reference 217. Furthermore, the ability of ��-TCP to store an electrical charge by electrical polarization was studied, and this material was found to have a suitable composition and structure for both ion conduction and charge storage.218 Pure ��-TCP never occurs in biological calcifications. Only the Mg-substituted form, called whitlockite[e] [��-TCMP-��-tricalcium magnesium phosphate, ��-(Ca,Mg)3(PO4)2], is found in dental calculi and urinary stones, dentineal caries, salivary stones, arthritic cartilage as well as in some soft tissue deposits.
26,84-86,219-222 However, it has not been observed in enamel, dentine or bone. In biomedicine, ��-TCP is used in calcium orthophosphate bone cements31,223-227 and other types of bone substitution bioceramics.203,228-235 Dental applications of ��-TCP are also known.236 Pure ��-TCP is added to some brands of toothpaste as a gentle polishing agent. Multivitamin complexes with calcium orthophosphate are widely available in the market, and ��-TCP is used as the calcium phosphate there. In addition, ��-TCP serves as a texturizer, bakery improver and anti-clumping agent for dry powdered food (flour, milk powder, dried cream, cocoa powder). Besides, ��-TCP is added as a dietary or mineral supplement to food and feed, where it is marked as E341 according to the European classification of food additives.
A prenatal development of rats during gestation was found to be sensitive to E341 (TCP) exposure.237 There is a good review on the toxicological properties of inorganic phosphates, where the interested readers are referred.238 Occasionally, ��-TCP might be used as inert filler in pelleted drugs. Other applications comprise Anacetrapib porcelains, pottery, enamel, use as a component for mordants and ackey as well as a polymer stabilizer.129 ��-TCP of a technical grade (as either calcined natural phosphorites or bone dust) is used as a slow-release fertilizer for acidic soils.