Comparison of tetrazolium colorimetric and 51Cr release assays for cytotoxicity determination of dental biomaterials

Objectives. The purpose of this study was to compare a methylthiazole tetrazolium (MTT) dye colorimetric method with the standard 51Cr assay as methods of assessing cytotoxicity of dental materials. Methods. Two MTT-based colorimetric formats, test tube and 96-well microplate methods, were compared to the 51Cr release assay. A series of eigth dental materials were evaluated. Cytotoxicity profiles were determined for each test material. A TC50 value (Toxic Concentration required to kill 50% of the cells) was determined for each biomaterial, and these results were used to make statistical comparisons between the methods. Results. The three methods were statistically correlated (p < 0.005) by comparison of the eight samples tested. That is, the same rank in toxicity was given by the two tetrazolium sample formats and the 51Cr method. Significance. The MTT assay was found to have several advantages in comparison to the current standard 51Cr release assay. Optimized in the 96 well format, complete dose response curves and greater sample comparisons can be made rapidly, making the MTT method more economical in time and cost. Furthermore, the MTT method is based on intracellular biochemical changes, measuring cell viability rather than cell morbidity, and has lower detectable limits than the 51Cr release method. There is also less detector chemical binding interference than encountered in the 51Cr release method.