The mechanical properties of calcium phospate ceramics modified by collagen coating and populated by osteoblasts.

Bioceramics containing hydroxyapatite (HA), tricalcium phosphate (TCP) or composites which combine the best properties of both materials are among the principal candidates for bone replacement grafts. In this study we have investigated the mechanical strength of HA, TCP and composites of the two in the ratios 75;25 (H75), 50:50 (H50) and 25:75 (H25). The strength of each material was investigated in the presence and absence of collagen coating, and the influence of osteoblast culture for up to 28 days on strength was determined. TCP, H25 and H75 were significantly weakened by collagen coating, the strengths of the other materials were either not affected (HA) or increased (H50). Culture with osteoblasts significantly increased the strength of uncoated HA and H50, but this effect was not observed when the materials were coated with collagen. Our results indicate that ceramic composition affects the interactions between collagen coating, culture with osteoblasts and mechanical strength of the material. Although collagen coating has been found to increase the proliferation of osteoblasts into these ceramic materials, it may be necessary to stabilise and optimise the coating process to minimise effects on mechanical strength.