Stimulatory effect of zinc-releasing calcium phosphate implant on bone formation in rabbit femora

Although hydroxyapatite (HAP) and tricalcium phosphate (TCP) are currently used as bone graft substitutes or coatings on metallic prostheses because o f their excellent biocompatibility and osteoconductivity, they do not stimu late bone formation or inhibit bone resorption. Zinc, an essential trace el ement in many animals, has a direct specific proliferative effect on osteob lastic cells and has a potent and selective inhibitory effect on osteoclast ic bone resorption in vitro. Therefore, zinc-containing p-tricalcium phosph ate (ZnTCP) ceramics and composite ceramics of ZnTCP and HAP (ZnTCP/HAP) we re implanted in the femora of New Zealand White rabbits for il weeks to pro mote bone formation. The implants were sintered ceramics with zinc contents of 0 (control), 0.063, 0.316 and 0.633 wt %. Histological and histomorphom etrical investigation of the undecalcified sections revealed an increase by 51% (p = .0509) in the area of newly formed bone around the ZnTCP/HAP impl ants of 0.316 Zn wt % compared with the control. Plasma zinc concentration was unchanged. An increased bone resorption on the endosteal surface was ob served when ZnTCP and ZnTCP/HAP of 0.633 Zn wt % were implanted. To promote bone formation, the optimum zinc content of the calcium phosphate ceramics was therefore 0.316 wt %. (C) 2000 John Wiley & Sons, Inc.