Classically, the biocompatibility of an implanted material has been described in terms of the morphological appearance of the inflammatory reaction to the material. Therefore, histologic evaluation of the tissues adjacent to the implanted materials as a function of implantation time has been the most commonly used method of evaluating the biocompatibility of a material. Our choice of different implant models for animal experiments depends on the kind of material and its application. In our histological lab paraffin and methylmethacrylate sections are prepared from tissues acquired in animal experiments or patient biopsies. For bone specimens mostly undecalcified embedding is used.
Many special stains are available.
Microradiographs and evaluation of sequential polychrome markers by tetracyclines can also be performed. The CT provides the 3-dimensional measurement of density distribution. Additionally, the integration of a material and the surrounding bone can be evaluated by biomechanical methods which include the measurement of the relative motion between bone and implant surfaces, shear strength and push out strength. A very sensitive method for testing the toxicity of biomaterials and their degradation products is the assessment of in vitro toxicity. In vitro cell culture methods have the advantage of relatively well-controlled variables and are generally accepted as a very effective method for biocompatibility testing.