Characterization and bioactivity of tape-cast and sintered TCP sheets

The purpose of this study was to investigate the influence of sintering temperature on in vivo and in vitro bioactivities of sintered tricalcium phosphate (TCP) sheets prepared by the tape casting technique. Green sheets of beta-TCP prepared by tape casting were sintered for 2 h in a furnace at atmospheric pressure, at five different sintering temperatures: 900, 1000, 1100, 1150, and 1200 degrees C. Measurement of X-ray diffraction and Fourier transform infrared spectrometry showed the presence of alpha-tricalcium phosphate phase in the TCP sheet sintered at 1200 degrees C, in addition to beta-TCP phase. As compared with the other sintered TCP sheet, the TCP sheet sintered at 1200 degrees C demonstrated a lower dissolution rate in phosphate buffered saline solution at 37 degrees C and pH 7.4 over 24 weeks, and more amount of apatite formation in Hanks' balanced salt solution with pH 7.4 was observed. After 4 weeks' implantation of sintered TCP sheets into tibial diaphyses of rabbits, the bone-sheet contact of the TCP sheet sintered at 1200 degrees C was significantly higher than that of the TCP sheet sintered at 900 degrees C. These results indicate that a flat sintered TCP sheet prepared by tape casting is a promising material for a bone substitute.