Abstract: OBJECTIVE: To evaluate the in vitro cytotoxic effects of tongue depressors with different materials and their scientific bases for toxicity. METHODS: The L929 cell line was cultured and organized into different groups:blank control, negative control, positive control and treatment groups. The latter group was treated with tongue depressors of the three materials with 25%, 50%, 75% and 100% extraction concentrations. After 24 h of treatment, all cell cultures were evaluated for their morphology under a microscope, viability using the MTT method and other cytotoxic effects. RESULTS: The results showed that cells in the positive control group and in the group which was treated with the 100% extract from wooden tongue depressors were completely destroyed. On the other hand, cells in the group which was treated with 100% extract from bamboo tongue depressor grew normally. Approximately 20% of the cells in the group which was treated with 100% extract from stainless steel tongue depressor showed abnormal morphologies:round with shrinkage, poor adherence to the wall and lacking intracellular particles. Results from the MTT assay show that the cell viability for the mentioned two groups which indicated toxicity were 89.1% (bamboo) and 81.2% (stainless steel). According to criteria of cytotoxicity, exposure to extracts from wooden tongue depressors caused potential cytotoxicity. CONCLUSION: Our results indicate that tongue depressors which were made of certain materials caused cytotoxic effects in vitro. Our data should be useful in strengthening safety guidelines for use of these tongue depressors.

Key words: tongue depressor, L929 cell, cytotoxicity, MTT