423 Osseointegration of macroporous calcium phosphate ceramics having a different chemical composition P. Fray&net, J.L. Trouillet*, N. Rouquet, E. Azimus* and A. Autefage* Bioland Inc., 132 Rte d’Espagne, 31100 Toulouse, and “Ecole Nationale V&&inaire de Toulouse, Toulouse, France Calcium phosphate macroporous ceramics are biocompatible for bone surgery. Their osseointegration is, however, sometimes very poor. To measure the effect of the calcium phosphate content of the ceramic on its osseointegration, macroporous ceramics, differing in their chemical composition, were implanted into sheep femurs. The ceramics were composed of different percentages of hydroxyapatite (HA) and /Ltricalcium phosphate (P-TCP). All other characteristics were the same. Results were assessed histologically with image analysis and showed significant differences in the amount of bone formed at the contact of the different ceramics. Ceramics containing /LTCP induced better osseointegration than pure HA ceramics. Keywords: Ceramics, hydroxyapatite, tricalcium phosphate, osseointegration Received 27 October 1992; accepted 9 November 1992 Calcium phosphate ceramics, especially hydroxyapatite (HA) ceramics, are used as bone-filling biomaterials’-5, As with the manufacturing process of every ceramic material, three main stages are required for their elaboration”. The material, initially in a powder form, is shaped at room temperature into the definitive part: for the third stage, the part is sintered to obtain the fusion of the grains of the material and eliminate the internal microporosity. During this process, the physical and chemical characteristics of the material can change. The final calcium phosphate material can have very different characteristics. One of these is the chemical composition of the material. This depends only partly on the composition of the initial powder. Non-stoichiometric HA is relatively unstable. At ca. 900°C, some other phases (tricalcium phosphate, calcium oxide) can appear’, ‘, Even perfectly stoichiometric HA may give rise to an oxyhydroxyapatite at temperatures >lOOO”C or to tricalcium phosphate and tetracalcium phosphate at >157O”C. Analysis of commercially available HA for bone substitution showed that the chemical composition of the material was different from that of a supposedly pure HA9 (N. Rouquet, unpublished data). A variable amount of p-tricalcium phosphate (p-TCP) phase was found in most of the specimens analysed. To evaluate the influence of this phase on the osseointegration of calcium phos- phates, we implanted calcium HA ceramics, differing Correspondence to Dr P. Frayssinet. only in the amount of P-TCP in the material, into sheep. Implants were then histologically analysed after different periods of implantation. MATERIALS AND METHODS zyxwvutsrqponmlkjihgfedcbaZYXW Macroporous calcium phosphate ceramics Pure HA powder (Bioland, France] was obtained by a double decomposition method. Pure P-TCP powder (Bioland, France) was blended with HA powder to obtain two different powder mixtures, containing 75% HA-25% /3-TCP and 50% HA-50% /?-TCP, respectively. The macroporous specimens were manufactured according to classical processes. A slurry made from the different powders, water and additives, was prepared. This solution was then manipulated to obtain an initial ceramic shape. The final sintering stage gave a 100% crystalline calcium phosphate material. Using this technique, cylinders with a diameter of 0.9 cm and a length of 1 cm were made. A porosity consisting of interconnecting macropores from 300 up to 1500 pm was produced. The resulting porosity was 70%. Three types of implants were made, each having a different calcium phosphate phase composition. Their TCP:HA ratio was 0,0.3 and 1. All the manufacturing processes, except the composition of the powder, were the same. The com- position of the specimen was assessed by X-ray diffraction (quantitative determination) (Figure 1). 0 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA 1993 Butterworth-Heinemann Ltd Biomaterials 1993, Vol. 14 No. 6 0142-9612/93/060423-07