Tissue reaction of rats and guinea-pigs to Co-Cr implants with different surface finishes.

An investigation was carried out with the following objects: (a) To study the effect of different surface textures of metallic implants upon the s.c. tissues of rats and guinea-pigs; (b) to compare the reaction of the s.c. tissues of the rat with the reaction of the s.c. tissues of the guinea-pig following implantation of similar solid state materials. Two cylindrical Co-Cr-Mo implants, measuring 0·4 in. long and 0·1 in. in diameter were implanted, one on either side of the mid-line, in the dorso-lumbar region of 36 rats and 36 guinea-pigs. The implants on the right side had a rough surface texture and the implants on the left side a smooth surface texture. The tissue reaction around the implants was examined microscopically and macroscopically at intervals of 2, 4, 7, 14, 42 and 84 days following implantation. During the initial inflammatory process minor differences were observed in the tissue reaction around rough and smooth implants. However, these differences were considered to be within normal biological variation. At 84 days calcified material was observed around a rough implant in a guinea-pig. Apart from this isolated finding, the tissue reaction around the rough and smooth implants was similar. At 84 days all the implants were surrounded by a fibrous connective tissue capsule which was relatively thick and loosely woven in the rat and which was thin and compact in the guinea-pig. The vascularity and cellularity around the implants were slightly more evident in the rat than in the guinea-pig. However it was observed that the vascularity and cellularity of normal rat tissue was also more evident than that of normal guinea-pig tissue.