Fabrication of fluoride-substituted carbonate apatite ceramic

The long-term objective of our study is to develop calcium phosphate biomaterials incorporating optimum levels of magnesium, zinc and fluoride (F). Separately, these ions have been associated with bone formation, biomineralization and osteoporosis therapy. Fluoride-substituted carbonate apatite (CFA) is the carrier of F. Currently only powdered CFA is available. Porous, dense or granular ceramic body of CFA is more valuable as a bone grafting material although no ceramic CFA is reported. Objectives: The purpose of this study is to fabricate a CFA ceramic. Methods: A CFA powder with CO₃ and F contents of 11.1 and 0.66 wt%, respectively, was mixed with a carbonate apatite powder with CO₃ content of 12.3 wt% at a weight ratio of 1:1. The mixed powder was uniaxially pressed at a pressure of 28 MPa, followed by sintering for 1-3 hours at 700 ºC in a CO₂ gas atmosphere. The sintered body was characterized by X-ray diffraction (XRD). CO₃ and F contents were determined by infrared (IR) spectroscopy and a F ion meter, respectively. Results: The CFA powder was successfully sintered into a microporous ceramic body. No decomposition product was detected by XRD. The IR spectra of sintered CFA had carbonate bands at 875, 1430 and 1460 cm^-1. CO₃ and F contents of the sintered CFA were 10.9 and 0.14 wt%, respectively, which were less than those before sintering. The CO₃ and F contents, however, were still 2-4 times higher than those of bone. Conclusion: CFA powder is sintered into a ceramic body without serious decomposition. The CFA ceramic body contains sufficient amounts of CO₃ and F. Supported by grant no. EB003070 from the NIBIB/NIH and by Grant-in-Aid for Scientific Research (C) no 16500310 from JSPS, Japan.