title: Resorbability and solubility of zinc-containing tricalcium phosphate.
abstract: Using zinc-containing tricalcium phosphate (ZnTCP) as the zinc carrier for zinc-releasing calcium phosphate ceramic implants promoted bone formation around the implants. Because no quantitative information was available on the equilibrium solubility and resorbability of ZnTCP, in vitro equilibrium solubility and in vivo resorbability of ZnTCP were determined and compared quantitatively in this study. The solubility of ZnTCP decreased with increasing zinc content. The negative logarithm of the solubility product (K(sp)) of ZnTCP was expressed as pK(sp) = 28.686 + 1.7414C - 0.42239C(2) + 0.063911C(3) - 0.0051037C(4) + 0.0001595C(5) in air, where C is the zinc content in ZnTCP (mol %). The solubility of ZnTCP containing a nontoxic level of zinc (<0.63 wt %) decreased to 52-92% of the solubility of pure tricalcium phosphate (TCP) in the pH range 5.0-7.4. However, the in vivo resorbed volume of ZnTCP containing the same amount of zinc was much lower than that expected from the in vitro solubility, becoming as low as 26-20% of that of TCP. Cellular resorption of TCP is substantially a process of dissolution in a fluid with an acidic pH that is maintained by the activities of cells. Therefore, the reduction of the resorbability of ZnTCP could be attributable principally to its lowered cellular activation property relative to that associated with pure TCP.
authors.affiliation: National Institute for Advanced Interdisciplinary Research, Ministry of International Trade and Industry, 1-1-4 Higashi, Tsukuba-shi, Ibaraki 305-8562, Japan. atsuo-ito@aist.go.jp
authors.forename: Atsuo
authors.initials: A
authors.lastname: Ito
authors.forename: Haruo
authors.initials: H
authors.lastname: Kawamura
authors.forename: Shunpei
authors.initials: S
authors.lastname: Miyakawa
authors.forename: Pierre
authors.initials: P
authors.lastname: Layrolle
authors.forename: Noriko
authors.initials: N
authors.lastname: Kanzaki
authors.forename: Gabin
authors.initials: G
authors.lastname: Treboux
authors.forename: Kazuo
authors.initials: K
authors.lastname: Onuma
authors.forename: Sadao
authors.initials: S
authors.lastname: Tsutsumi
mesh_terms: D000465:Algorithms; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry*; D002130:Calcium Phosphates / Q000737:chemistry* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008422:Materials Testing; D019736:Prostheses and Implants; D011817:Rabbits; D012995:Solubility; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001672:Biocompatible Materials; D002130:Calcium Phosphates; C485817:beta-tricalcium phosphate; D015032:Zinc; C018392:tricalcium phosphate