Tissue reaction to alumina implants inserted into the tibiae of rats

We examined the tissue reaction to three alumina implants--single-crystal alumina (SA), dense polycrystal alumina (DPA), and porous polycrystal alumina (PPA)--inserted transcortically, extending into the medullary canal of rat tibiae, and assessed the quantitative differences in bone reaction using an image processing system. There was no difference in the degree of maturation of newly formed bone around the three kinds of alumina. SA and DPA were encapsulated with a continuous bone layer, but some bone tissue was attached focally around PPA. Bone trabeculae in the control site diminished in size and number chronologically. Multinucleated giant cells were observed on the surface of DPA and PPA, but not on SA. Tabulation of the quantitative evaluation indicated that SA showed the highest, DPA a lower, and PPA the lowest in bone contact rate, bone contact thickness, and bone contact area. These data suggest that SA is superior to the other two as an implant material.