Zinc-containing a-tricalcium Phosphate Cement for Stimulating Bone Formation: A Preliminary Study

Zinc-containing b-tricalcium phosphate (Zn-bTCP) with optimum zinc content has been shown to promote bone formation [Kawamaura et al 2000]. Incorporation of Zn-bTCP in a calcium phosphate cement (CPC) resulted in higher level of proliferation of human osteoblastic cells, in vitro. Objectives: The purpose of this study was to prepare a Zn-CPC using Zn-aTCP and investigate its effect on bone formation in vivo. Methods: Zn-free aTCP or Zn-aTCP (containing 0.19 wt% Zn) powders, or their mixtures with zinc contents of 0.04, 0.08 and 0.11 wt% were used. All the powders were less than 20 mm in particle size with nearly the identical particle size distribution. These powders were mixed with a 12 wt% sodium succinate solution at a powder-to-liquid ratio of 2.0 and were set at 37 ° C in an atmosphere at 100 % humidity for 1 day followed by curing in pure water at 37 ° C. The set cements were implanted in medullary cavity of rabbit (New Zealand white) femora for 4 weeks. Bone formation was determined from histological sections. Results: All the implanted set cements prepared from Zn-aTCP (containing 0.04 to 0.11 wt% Zn) were associated with a higher osteoblastic activity and greater bone formation compared to those prepared from Zn-free aTCP. However, inflammatory reaction was also observed around those prepared from powders containing more than 0.08 wt% Zn. Conclusion: Zn-aTCP used in preparation of calcium phosphate cement promotes greater bone formation attributed to the Zn ions released. Studies are ongoing to determine the optimum Zn concentration. [Supported by Three Dimensional Tissue Module Project of METI, and Advanced Support System for Endoscopic and Other Minimally Invasive Surgery of the New Energy and Industrial Technology Development Organization (NEDO)].