Crystallization and microstructure analysis of calcium phosphate-based glass ceramics for biomedical applications

Calcium phosphate glasses and glass ceramics (CaO/P2O5 = 1.25 in molar rati o) modified by small amounts of additives such as Na2O, MgO, TiO2 and ZrO2 were prepared after appropriate heat treatment for nucleation and crystalli zation. Based upon differential thermal analysis (DTA) results, a two-step heat treatment was used for crystal nucleation and growth. X-ray diffractio n (XRD) analysis demonstrated that bioresorbable beta-Ca2P2O7 (beta-DCP), b eta-Na2CaP2O7, Na2Mg(PO3)(4) phases were formed in the glass matrix dependi ng upon the relative contents of the additives. By adding higher contents o f Na2O and TiO2 and using CaO/P2O5 = 1.5-2.0, crystallization of beta-DCP a nd Ca-3(PO4)(2) (beta-TCP), and the formation of a dense structure in the g lass ceramics were obtained. The precipitation of these crystals could be w ell distinguished at a magnification of 4000x and phases were dispersed in areas of micron size. A porous structure may be easily formed after the sol uble phases are dissolved in physiological media. These glass ceramics with high CaO/P2O3 ratio, modified by the above mentioned additives are expecte d to find use as implants for bone replacement/regeneration and drug delive ry carriers synergistically, because the soluble phases may act as drug del ivery carriers and the porous structure will allow for bone ingrowth. (C) 2 000 Elsevier Science B.V. All rights reserved.