Biological evaluation of dental restorative materials--a comparison of different test methods

Three restorative materials--two composite resins and zinc oxide-eugenol cement--were subjected to three cytotoxicity tests--chromium release, millipore filter, and agar overlay--one implantation test, and a pulp study. In the cytotoxicity test the materials were evaluated freshly prepared and after storage at 37 degrees C for 24 h. In the implant test polyethylene tubes holding freshly prepared materials were inserted subcutaneously into rats. After 30 and 90 days the tissue response at the end of the tube and at a window site along the side of the tube was assessed. In the pulp study the materials were placed in cavities prepared in newly erupted monkey teeth. After 7 and 78 days the reaction of the pulp tissue was studied. Comparison of the results from the cytotoxicity tests revealed a varying degree of correlation, indicating that the three tests were not interchangeable. When data from the pulp study were compared to those of the cytotoxicity tests and implantation test, the correlation was not as good. This emphasizes that the final biological evaluation of dental restorative materials still has to be carried out as pulp studies.