IN-VITRO STABILITY PREDICTIONS FOR THE BONE HYDROXYAPATITE COMPOSITE SYSTEM/

Electroacoustic measurements of the zeta (zeta) potential as a functio n of pH were collected and used to probe the nature of the ionic contr ibutions to the bond formed between synthetic hydroxyapatite (HA) and bone. HA powder and wet bone powder were dispersed into an electrolyte solution comprised of physiologic saline (0.154M NaCl), electroacoust ic measurements collected, and the zeta potential calculated as a func tion of FH. The zeta potential and particle size then were used to cal culate the stability of the composite dispersion, where stability is t he ability of a particulate suspension to remain unagglomerated. The s tability was used to predict the homo- (HA to WA and bone to bone) ver sus heterocoagulation (HA to bone) behaviors for the HA/bone system. A lthough single component bone and HA demonstrated stability against ag glomeration, the HA/bone interaction was determined to be unstable for all pH levels tested, including pH 7.4, the normal in vivo pH. These results establish one factor responsible for the observed physicochemi cal bonding between bone and HA noted by many in the orthopedic commun ity. (C) 1998 John Wiley & Sons, Inc.