An In Vitro Model for Studying Bioresorption Rate of Calcium Phosphate Bone Graft Materials

Published

October 16, 2008

Author(s)

Laurence C. Chow, Shozo Takagi, Milenko Markovic

Abstract

It has been postulated that the in vivo resorption rates of calcium phosphate bone graft materials are closely related to their dissolution rates in demineralizing solutions having ionic compositions mimicking the acidic environment produced by osteoclasts. Direct pH measurements of the extracellular fluid from bone resorbing cells-bone matrix interface showed that the pH was as low as 4.7. In the present study, a constant-composition dissolution system was used as an in vitro mineral resorption model to understand the factors that may control the resorption rate of calcium phopshate cements, a new class of self-hardening and bioresorbable bone defect repair materials. The types of CPC samples studied included (1) CPC comprised of stoichiometric OHAp(Ca/P = 1.67) and Ca-deficient OHAp (Ca/P = 1.50), (2) CPC with low and high microporosities (< 1 [mu]m), and (3) CPC with high and low macroporosities (> 100 [mu]m). Both microporosity and macroporosity promoted the rate of CPC dissolution but the role of Ca deficiency was not entirely clear. For a given type of CPC specimen, the dissolution rate was significantly greater at pH 4.5 than at pH 5.0. The findings suggest the possibility that CPC may be formulated to have the desired resorption rates for specific clinical applications. This in vitro model should also be useful in studying the factors that control resorption rates of other calcium phosphate biomaterials and coating.

Citation

Society for Biomaterials

Pub Type

Journals

Keywords

bioresorption, bone graft materials, calcium phosphate cement, dissolution, macroporosity, microporosity

Citation

Chow, L. , Takagi, S. and Markovic, M. (2008), An In Vitro Model for Studying Bioresorption Rate of Calcium Phosphate Bone Graft Materials, Society for Biomaterials (Accessed July 16, 2025)