frequency of bacteria and fungi isolated from pumice in dental laboratories

background: this study was conducted to determine the species of oral and non-oral microorganisms in dental laboratory pumice in order to undertake the necessary disinfection control protocols. methods: fourteen active and well-known dental laboratories of tehran entered our study. samples of pumice were collected from polishing containers in a completely sterilized and controlled condition. they were immediately sent to microbiology laboratory and were cultured in specific media in order to identify the aerobic and anaerobic bacteria and also genera of fungi. results: microorganisms recovered from pumice were shown in frequency order as follows: acinetobacter lowffi, bacillus cereus, staphylococcus aureus, pseudomonas aeruginosa, diphteroids, serratia mercescens, enterobacter aerogenes, morganella morgani, providencia rettgeri, staphy-lococcus albidus and streptococcus sanguis. therefore both oral and non-oral bacteria were visible. the isolated fungi were aspergillus niger, fusarium sp., aspergillus flavous, cephalosporium sp . and pencillium sp . conclusion: this study showed that polishing pumice was contaminated by both oral and non-oral bacteria and fungi. therefore, the chance of cross-contamination still severely exists, and measures should be conducted to prevent the contamination of technicians, dentists and patients.