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Abstract
RF magnetron sputter deposition was used to produce 0.1, 1.0 and 4.0 microm thick
Ca-P coatings on TiO(2)-blasted titanium discs. Half of the as-sputtered coated specimens
were subjected to an additional infrared heat treatment for 30s at 425-475 degrees
C. X-ray diffraction demonstrated that infrared radiation changed the amorphous 4
microm sputtered coatings into an amorphous-crystalline structure, while the amorphous
0.1 and 1 microm changed in a crystalline apatite structure with the presents of tetracalciumphosphate
as a second phase. Scanning electron microscopically examination of the sputtered
coatings revealed that annealing of the 4 microm thick coatings resulted in the appearance
of small cracks. Subsequently, the discs were implanted subcutaneous into the back
of rabbits. After 1, 4, 8 and 12 weeks of implantation, the implants were retrieved
and prepared for histological and physicochemical evaluation. Histological evaluation
revealed that the tissue response to all coated implants was very uniform. A very
thin connective tissue capsule surrounded all implants. The capsule was usually free
of inflammatory cells. At the interface, there was a close contact between the capsule
and implant surface and no inflammatory cells were seen. Physicochemical evaluation
showed that the 0.1 and 1 microm thick amorphous coatings had disappeared within 1
week of implantation. On the other hand, the 4 microm thick amorphous phase disappeared
during the implantation periods, which was followed by the precipitation of a crystalline
carbonate apatite. Further, at all implantation periods the heat-treated 1 and 4 microm
thick coatings could be detected. Occasionally, a granular precipitate was deposited
on the heat-treated 4 microm thick coating. Fourier transform infrared spectroscopy
showed the formation of carbonate apatite (CO(3)-AP) on the 4 microm thick amorphous
coating and on the heat-treated specimens. On basis of our findings, we conclude that
1 microm thick heat-treated Ca-P sputter coating on roughened titanium implants appear
to be of sufficient thickness to show bioactive properties, under in vivo conditions.