Elaboration conditions influence physicochemical properties and in vivo bioactivity of macroporous biphasic calcium phosphate ceramics

Two different preparations of biphasic calcium phosphate (BCP) were charact erized in vitro: BCP1 from a mechanical mixture of hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP) powders, and BCP2 from calcination of a calcium-deficient apatite (CDA). The structural, physicochemical and mech anical parameters of these two preparations were investigated, and two diff erent macroporous BCP1 (MBCP1) and BCP2 (MBCP2) implants were manufactured and implanted in rabbit bone for in vivo bioactivity studies. Scanning elec tron microscopy observations showed that MBCP1 implants had a significantly higher degradation rate (P<0.0001) than MBCP2 implants. This was probably caused by the presence of calcium oxide impurities in BCP1 and the more int imate mixture and stable ultrastructure of BCP2. No significant difference about the newly formed bone rate in these two BCP preparations was observed . Very slight variations in sintering conditions appeared to influence the biodegradation behavior of the two MBCP implants despite their identical HA /beta-TCP ratios and similar porosity. Precise and complete in vitro charac terization enabled us to understand and predict in vivo degradation behavio r. (C) 1999 Kluwer Academic Publishers.