Concepts in biocompatibility testing of dental restorative materials

Due to the diversity of adverse biological effects which might be caused by dental restorative materials, biocompatibility assessment cannot rely on a single test but has to be based on a planned and structured approach (concept). First, the possible harm evoked by the material, the known data, and suitable biological and other test methods available must be taken into consideration. Modern regulatory concepts require for this purpose the services of experts to propose the appropriate set of required tests for a given material. The use of standards is generally emphasized because of better comparability of the data. Other tests may be chosen if more appropriate. Modern scientific concepts of biocompatibility testing are based on the need for rapid and cost-effective test methods, avoiding animal tests whenever possible. While formerly in vitro experiments did not take into account the special clinical situation in which the material would be used, modern concepts try to simulate important parameters of the in vivo situation as closely as possible. This may be achieved, for example, by including suitable barriers between the material and the target cells, by constructing appropriate target cells, and by choosing clinically relevant markers for measuring the biological effects caused by the material. There are indications so far that through this approach the number of animal tests can be reduced. The use of these methods may also lead to a better understanding of the mechanisms behind the biological reactions (mechanistic approach) in describing the biocompatibility of dental restorative materials.