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 p repared, The calcium/phosphorus molar ratios were 1,1.5, 1.66 and 2, r espectively. Particles (150-300 mu m) of these ceramics were packed in to holes (diameter 2.5 mm) made in the tibial metaphysis of mature mal e rats. At 2 weeks, 4 weeks, 8 weeks and 6 months after the operation, undecalcified specimens were prepared. Transmission electron microsco py showed that the bone-bonding behaviour of calcium phosphate ceramic s at the interface with bone did not vary with the calcium/phosphate m olar ratio. Amorphous substances or needle-like microcrystals were obs erved on the surface of the ceramics at 2 weeks after implantation. Th e ceramics showed direct continuity with small crystallites of bone ti ssue at 4 weeks, 8 weeks and 6 months after implantation. The ceramics appeared to be getting smaller with time. Collagen fibres were not ob served at the bone/ceramic interface. Neither chemical bonding nor mec hanical bonding by interlocking between bone and ceramics was describe d by morphological observation using transmission electron microscopy.