Bio-compatibility in selection of materials for implantation.

In this paper the factors which contribute importantly to incompatibility and functional failure of implant materials are examined. The interaction of these criteria in the etiology of implant failure is discussed in terms of the host response to an inert implant and the modulation of this response in the presence of cytotoxic sequellae. Cellular injury either of traumatic or biochemical origin is seen to stimulate sequestration of the offending implant by fibrous tissue. Difficulties associated with routine quantification of such response by animal implantation studies have led to development of rapid in vitro techniques to predict the quantity and cytotoxicity of moeities released by an implant. These techniques are based on infrared analysis and primary mammalian tissue culture with a pseudo body fluid to which materials are exposed at elevated temperature. The protocols allow formulation of rational criteria for rejection of candidate materials for clinical implantation and acceptance for definitive preclinical animal implant studies. The procedures are applicable for routine monitoring of materials accepted for fabrication of prototype or production implants and of fabricated prostheses.