BONE-BONDING BEHAVIOR OF PLASMA-SPRAYED COATINGS OF BIOGLASS(R), AW-GLASS CERAMIC, AND TRICALCIUM PHOSPHATE ON TITANIUM-ALLOY

The bone-bonding behavior of three kinds of bioactive ceramics coated on titanium alloy by the plasma-spray technique was investigated. Tita nium alloy (Ti-6A1-4V) coated with Bioglass(R) (45S5), apatite-wollast onite containing glass ceramic (AW), or beta-tricalcium phosphate (TCP ) was prepared, and rectangular specimens were implanted into the tibi al bones of mature male rabbits, which were sacrificed 8 or 24 weeks a fter implantation. The tibiae containing the implants were dissected o ut and subjected to detachment tests to measure the failure load. The bone-implant interface was investigated by Giemsa surface staining, co ntact microradiography, and scanning electron microscopy-electron prob e microanalysis (SEM-EPMA). Eight weeks after implantation, the failur e loads for implants coated with Bioglass(R), AW, and TCP were 1.04 +/ - 0.94, 2.03 +/- 1.17, and 3.91 +/- 1.51 kg, respectively, and 24 week s after implantation, the respective failure loads were 2.72 +/- 1.33, 2.39 +/- 1.30, and 4.23 +/- 1.34 kg. Failure loads of AW- and TCP-coa ted implants did not increase significantly with time. After the detac hment test, breakage of the coating layer was observed. Bioactive cera mics can act as stimulants that induce bonding between bone and metal implants. However, failure load of metal implants coated with the bioa ctive ceramics was lower than that of bulk AW or TCP. It appears impos sible to obtain a higher failure load using a bioactive-ceramic coatin g on titanium alloy. Histologically, the coating layer was found to be come detached from the metal implant and the bone tissue bonded to the coating layer. SEM-EPMA observation revealed breakage of the coating layer, although bonding between bone and the coating layer was evident . A Ca-P-rich layer was observed at the interface between bone and the AW coating, and a Ca-P-rich and a Si-rich layer were observed at the interface between bone and the Bioglass(R) coating. For clinical appli cation, it would seem better to use coated metal implants for short-te rm implantation. However, there is a possibility of breakage of the co ating layer because of both dissolution of the bioactive ceramic and m echanical weakness at the interface between the coating layer and the metal implant. (C) 1996 John Wiley & Sons, Inc.