TRANSMISSION ELECTRON-MICROSCOPY OBSERVATIONS AT THE INTERFACE OF BONE AND 4 TYPES OF CALCIUM-PHOSPHATE CERAMICS WITH DIFFERENT CALCIUM PHOSPHORUS MOLAR RATIOS

Four kinds of calcium phosphate ceramics, beta-calcium pyrophosphate (Ca2P2O7), beta-tricalcium phosphate (Ca-3(PO4)(2)), hydroxyapatite (Ca-10(PO4)(6)(OH)(2)) and tetracalcium phosphate (Ca-4(PO4)(2)O), were prepared, The calcium/phosphorus molar ratios were 1,1.5, 1.66 and 2, respectively. Particles (150-300 mu m) of these ceramics were packed into holes (diameter 2.5 mm) made in the tibial metaphysis of mature male rats. At 2 weeks, 4 weeks, 8 weeks and 6 months after the operation, undecalcified specimens were prepared. Transmission electron microscopy showed that the bone-bonding behaviour of calcium phosphate ceramics at the interface with bone did not vary with the calcium/phosphate molar ratio. Amorphous substances or needle-like microcrystals were observed on the surface of the ceramics at 2 weeks after implantation. The ceramics showed direct continuity with small crystallites of bone tissue at 4 weeks, 8 weeks and 6 months after implantation. The ceramics appeared to be getting smaller with time. Collagen fibres were not observed at the bone/ceramic interface. Neither chemical bonding nor mechanical bonding by interlocking between bone and ceramics was described by morphological observation using transmission electron microscopy.