Ultrastructure of the interface between titanium and surrounding tissue in rat tibiae--a comparison study on titanium-coated and -uncoated plastic implants

Purposes The purposes of this study were to prepare experimental titanium‐coated plastic implants suitable for electron microscopy examination of the titanium‐bone interface and the response of tissue surrounding titanium, and to histologically compare surrounding tissue responses in coated and uncoated implants. Materials and Methods Experimental plastic implants were prepared from a plastic rod coated with a thin film of titanium. Plastic implants without coatings were used as controls. The implants were placed into tibiae of 10‐week‐old male rats. The specimens with implants were harvested 4 weeks after placement and observed under a light microscope, a transmission electron microscope, and a scanning electron microscope. Results In the transmission electron microscopy, the titanium layer of the experimental implant was a uniform layer that was approximately 150‐ to 250‐nm wide. The new bone formation was observed around both titanium‐coated implants and plastic implants. However, there was no direct bone contact with the plastic implant. Discussion The responses of tissue surrounding the experimental implants varied. Under an electron microscope, the following areas were observed: (1) an area with a direct contact between the titanium and bone, (2) an area at the interface where an amorphous layer was observed, (3) an area with progressing calcification in the surrounding tissue where the cells were adjacent to the titanium surface, and (4) an area in which bone resorption and apposition were observed and remodeling was thought to be occurring. Conclusion The experimental titanium was homogenous and was considered to be highly useful in observing the responses of the surrounding tissue to the titanium surface.