SummaryAdult albino rabbits were implanted with 304 stainless steel discs and cylinders (rods) in the following sites: beneath periosteum of the anterior calvarium, under the masseter muscle of the left mandibular ramus and in the body of the sacrospinalis muscle. (1) The tissue reaction around the disc implants was compared with that observed around the cylinder implants through the study of histological sections. (2) The degree of reactions observed at the various sites was contrasted with that seen at the other sites. In all cases the muscle implants showed the greatest reaction. Discs showed many micro areas of tissue reaction randomly around their periphery. I n contrast all the rod shaped implants in muscle showed a greater reaction towards the ends than in the mid portion of the shaft (clubbing) but rods implanted at other sites did not show this phenomenon. The results show that much of the histological tissue reaction seen around muscle implants is really caused by mechanical trauma which must be differentiated from a non-compatibility reaction. It is important to choose a test site where mechanical trauma will be minimal (submasseteric site) and use an implant shape (discs) which will not produce clubbing.Biological materials used in medicine and dentistry have undergone much investigation over the last three decades. While much effort has been directed towards defining the mechanical characteristics of

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An analysis of the tissue sections from previous implant studies was performed define additional criteria which could be considered in determinations of biocompatibility of implant materials. Adult albino rabbits were implanted with biomaterials in the sacrospinalis muscle for periods of 2, 6, 18, and 54 weeks. Fourteen different implant materials were used in this study. The tissues were examined histologically for the appearance of adipose fat cells within the membrane surrounding the implant as an important criterion of tissues implant compatibility. The results were compared with other previously used criteria in judging biocompatibility of implant materials. For the most compatible nonreactive materials, adipose tissue formation within the pseudomembrane began at 6 weeks and was quite extensive at 54 weeks. The reactive materials studied by us did not exhibit this phenomenon.

SummaryAdult albino rabbits were implanted with disks of 316 and 304 stainless steel in the subperiosteum of the anterior calvarium and the left mandible and in the left paravertebral and thigh muscles. The corresponding opposite sites were sham operated. The histopathological slides revealed that there was variation in thickness of the membrane in sections of both the paravertebral and thigh muscles; one side showing greater reaction than the other, which corresponded with the appearance of the implants. Sections of the calvarium revealed minimal bone and soft tissue reaction, although the implants showed corrosion compatible with soft tissue sites. The mandibular sections revealed extensive bone tissue reactions with minimum masseter muscle reactions, but the appearance of the implants due to corrosion was different than those of all other sites. Moderate eosinophilic infiltration was observed in sections containing deposits of corrosion products.