Clinical applications of dental prosthesis mainly focus on base metal alloy porcelain-fused metal restoration. The biological risks of using base metal alloys are generally known. Evaluation of alloy biocompatibility includes cytotoxicity tests prior to animal tests and clinical trials. Cytotoxicity assays include the neutral red test, 51Cr release assay, molecular filter test, methyl thiazolyl tetrazolium(MTT) colorimetric assay, cell counting kit-8(CCK-8) test, lactate dehydrogenase test, hemolysis test, and flow cytometry. The most widely used cells are L929 cells and HeLa cells. Toxicity tests on cell cultures are conducted through direct- and indirect-contact methods. Animal tests can produce immune responses or complementary activation; however, such tests are difficult to control, expensive, and time-consuming. Nevertheless, animal tests can simulate comprehensive responses, which are difficult to obtain from cytotoxicity tests. Thus, both cytotoxicity and animal tests are essential for biological compatibility evaluations of oral materials.
