APATITE CEMENTS

Ma PX, Zhang R, Xiao G, Franceschi R (2001) Engineering new bone tissue in vitro on highly porous poly (alpha-hydroxyl acids)/hydroxylapatite composite scaffolds. J Biomed Mater Res 54 284-293 Macdonald A, Moore BK, Newton CW, Brown CE (1994) Evalrration of an apatite cement as a root end filling material. J Endodontics 20 598-604... 

Fernandez E, Vlad MD, Gel MM, Lopez J, Torres R, Cauich JV, et al. Modulation of porosity in apatitic cements by the use of alpha-tricalcium phosphate-calcium sulphate dihydrate mixtures. Biomaterials. 2005 Jun 26(17) 3395—404. 

TetsuyaYussa, Youji Miyamoto, Kunio Ishikawa, MasaakiTakechi,YukihiroMomota, Seiko Tatehara, and Masaru Nagayama. Effects of apatite cements on proHferation and differentiation of human osteoblasts in vitro. Biomaterials 2004 25 1159-1166. 

Synthesis and in Vitro Cell Compatibility of a-Tricalcium Phosphate-Based Apatite Cement Containing Tricalcium Silicate... 

Keywords— Apatite cement, a-tricalcium phosphate. Tricalcium silicate. Silicate, Setting properties. In vitro. 

Apatite cement (AC) based on calcium phosphates offer an advantage for being freely moldable aM adaptable to the surface of bone defect. In addition, they have excellent biocompatibility because of their similarity to the inorganic component of the calcified tissue of the body [1,2], The first AC, reported by Prof Moruna and Kanazawa in 1976 was based in a-tricalcirrm phosphate (a-TCP, a-Ca3(P04)2), the cement converted to calcimn deficient HAp (CDHAp, Ca9(P04)s(0H)2) at a temperature below 100°C [3], Setting... 

Mori, A., Ohtsuki, C., Sugino, A., Kuramoto, K., Miyazaki, T., Tanihara, M. and Osaka, A. (2003)Bioactive PMMA-based bone cement modified with methacryloxypropyltrimethoxysilane and calcium salts — Effects of calcium salts on apatite-forming ability. Journal of the Ceramic Society of Japan, 111, 738-742. 

Other types of cements include anhydrite, barite, pyrite, iron hydroxides haematite, albite and apatite and are subordinate. 

Cement, dentin, and enamel are bone-like substances. The high proportion of inorganic matter they contain (about 97% in the dental enamel) gives them their characteristic hardness. The organic components of cement, dentin, and enamel mainly consist of collagens and proteoglycans their most important mineral component is apatite, as in bone (see above). 

Figure 3. A pie-shaped section of an osteon. The osteonal canal is on the upper right, the cement line to the left. The osteonal canal is part of the vascular porosity (PV), the lacunae and the canaliculi are part of the lacunar-canalicular porosity (PLC) and the material in the space that is neither PV or PLC contains the collagen-apatite porosity (PCA).The three interfaces, the cement line, the cellular interface (IC) and the lacunar-canalicular interface are each indicated. The radius of an osteon is usually about 100 mm, and the long axis of a lacuna is about 15 mm. Using this information it should be possible to establish the approximate scale of the printed version of this illustration. Previously published in Cowin (1999).

Materials that are compatible with biomtneralized phosphates (see Section 7.2) may be useful for implants A variety of synthetic calcium phosphates have been investigated. Ca3(P04)2 can be used as a biodegradable bone implant, which is gradually replaced by autogenous bone, and less degradable apatite implants can attach to natural bone without inflammation. Bioinert zinc phosphate cements are used in prosthetic dental applications. 

Phosphates are found in soft organic tissues as phosphate esters, and in hard tissues, notably bones and teeth, as solid calcium orthophosphates see Biomineralization). Hard tissues are composites of Apatite and an organic matrix collagen in bone, dentin, and dental cement, and keratin in dental enamel. The Apatite phases are defective with Ca/P ratios of 1.6-1.8 and can incorporate other cations (Na+, K+, Mg +) or anions (F , d , COs ", citrate). 

Calcium phosphate apatite formulations that are available commercially from different suppliers exhibit high chemical variability. Thus, manufacturers of apatite for biomedical applications often produce their own powder. Furthermore, synthesis enables a range of chemical substitutions, crystal sizes, shapes and forms (separate crystals or cements, as discussed in the next section). Various reviews cover synthesis methods (Narasaraju and Phebe 1996, Le Geros et al. 1995, Orlovskii and Barinov 2001). 

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