Tetracalcium phosphate

This reaction describes the formation of self-setting bone cement used ubiquitously in dentistry (Brown and Chow, 1987 Posset et al., 1998). A TEM (transmission electron micrograph) study of the conversion of TTCP to hydroxyapatite whiskers in contact with diammonium hydrogen phosphate solution was provided by Wang, Lin and Ju (2005). 

---

When freshly mixed, the carboxyHc acid groups convert to carboxjiates, which seems to signify chemical adhesion mainly via the calcium of the hydroxyapatite phase of tooth stmcture (32,34—39). The adhesion to dentin is reduced because there is less mineral available in this substrate, but bonding can be enhanced by the use of minerali2ing solutions (35—38). Polycarboxylate cement also adheres to stainless steel and clean alloys based on multivalent metals, but not to dental porcelain, resin-based materials, or gold alloys (28,40). It has been shown that basic calcium phosphate powders, eg, tetracalcium phosphate [1306-01-0], Ca4(P0 20, can be substituted for 2inc oxide to form strong, hydrolytically stable cements from aqueous solution of polyacids (41,42). 

Polymeric Calcium Phosphate Cements. Aqueous solutions of polymers such as poly(acryHc acid), poly(vinyl alcohol), gelatin, etc, and/or autopolymerizable monomer systems, eg, 2-hydroxyethyl methacrylate, glycerol dimethacrylate, calcium dimethacrylate, etc, have been used as Hquid vehicles (41,42,76) for the self-setting calcium phosphate cement derived from tetracalcium phosphate and dicalcium phosphate [7757-93-9J. 

Since calcium oxide is more than sparsely soluble and its reaction with phosphoric acid or a soluble phosphate is highly exothermic, researchers have used less soluble salts of calcium to react with the phosphates and form a phosphate ceramic [4-12]. In the acidic medium of the phosphate solutions, the salts of calcium dissolve slowly and release Ca (aq) into the solution, which subsequently reacts with phosphate anions and forms calcium phosphates. The best calcium minerals for forming CBPCs are combination of oxides of calcium and insoluble oxides such as silica or alumina, e.g., calcium silicate (CaSi03) and calcium aluminate (CaAl204), or even a phosphate of calcium such as tetracalcium phosphate (Ca4(P04)2 0). These minerals are reacted with acid phosphate salts to form phosphate cements. 

Ceramics Tetracalcium phosphate Dental cement Bioresorbable Barounian, Hesaraki and Kazemzadeh (2012)... 

Hydroxyapatite Calcium-metal phosphates Tricalcium phosphate Tetracalcium phosphate Bioglass... 

Calcium (titanium, zirconium) orthophosphate ceramics show solubility in SBF at least one order of magnitude lower than that of other calcium orthophosphates including hydroxyapatite and, in particular P-tricalcium phosphate (TCP) and tetracalcium phosphate (TTCP) (Figure 4.20). 

Figure 4.21 Solubility isotherms of calcium phosphates at 25 °C. HAp, hydroxyapatite DCPD, brushite DCPA, monetite p-TCP, p-tricalcium phosphate OCP, octacalcium phosphate and TTCP, tetracalcium phosphate. (After De Groot et al. (1990).)...

Posset, U., Locklin, E., Thull, R., and Kiefer, W. (1998) Vibration spectroscopic study of tetracalcium phosphate in pure polycrystalline form and as a constituent of a... 

Wang, I.C., Lin, J.H.C., and Ju, C.P. (2005) Transmission electron microscopic study of tetracalcium phosphate surface-treated with diammonium hydrogen phosphate solution. Mater. Trans., 46 (4), 885—890. 

Ca0-P205 in the absence of water (Kreidler and Hummel, 1967). The inset shows the region of interest, that is, the incongruent thermal decomposition of hydroxyapatite (Ca/P = 1.67) to a -tricalcium phosphate (Ca/P = 1.5) and tetracalcium phosphate... 

To study the thermal decomposition of hydroxyapatite towards tricalcium and tetracalcium phosphates, standard Raman spectra obtained from phase-pure TTCP, P-TCP and hydroxyapatite (HAp) can be collected as shown in Figure 7.9. 

Information on the degree of disorder introduced by thermal treatment of hydroxyapatite during plasma spraying could be obtained by NMR spectroscopy. The positions and shift of 1H-MAS and 31P-MAS NMR peaks are indicative of the environment of the P043- tetrahedra in calcium orthophosphates and allow distinguishing between dehydroxylation (oxyhydroxyapatite) and decomposition (tricalcium phosphate, tetracalcium phosphate) products of hydroxyapatite. 

Tetracalcium phosphate Ca4(P04)20 Used in some bone cements... 

Among the newer materials advocated for root canal sealing and reviewed by Chow et al. [16] is an apatitic calcium phosphate cement formed under ambient conditions from calcium hydrogen phosphate and a tetracalcium phosphate formally composed of equimolar quantities of CaO and Ca3(P04)2 ... 

Ishikawa K. Effects of spherical tetracalcium phosphate on injectability and basic... 

Kurashina K, Kurita H, Hirano M, Kotani A, Klein CP, de Qroot K. In vivo study of calcium phosphate cements implantation of an alpha-tricalcium phosphate/ dicalcium phosphate dibasic/tetracalcium phosphate monoxide cement paste. Biomaterials. 1997 Apr 18(7) 539-43. 

---