- The MTT assay is the most commonly utilized method to assess the cytotoxicity of dental materials in accordance with ISO guidelines.
- This assay measures cell viability by evaluating the metabolic activity of cells.
- The principle is based on the reduction of the yellow tetrazolium salt (MTT) into insoluble purple formazan crystals by mitochondrial enzymes of living cells.
- The amount of formazan produced correlates directly with the number of viable cells, making it a reliable indicator of cytotoxic effects.

- In contrast, other assays listed, such as the Ames test, are primarily used for mutagenicity testing, while the Comet assay assesses DNA damage at the cellular level.
- The Trypan blue exclusion test is used for a quick evaluation of cell viability by membrane integrity but is less sensitive and quantitative compared to the MTT assay.

Hence, the MTT assay combines sensitivity, reproducibility, and standardization, which aligns with the stringent requirements of ISO 10993-5 for biological evaluation of medical and dental devices.

Reference: Textbook of Dental Materials, Volume 1, Chapter 7: Biocompatibility and Cytotoxicity Testing, Page 145-147