Bacterial contamination of four commonly used dental materials Dr. M. Ghavam* - Dr. M. Aligholi** *- Associate Professor of Operative Dentistry Dept. - Faculty of Dentistry – Tehran University of Medical Sciences. **- The member of Microbiology Dept. Faculty of Medicine – Tehran University of Medical Sciences. Background and Aim: Bacterial contamination of dental materials and devices used in dental clinics and laboratories can lead to infectious diseases in patients, dentists and dental care providers. The aim of this study was to examine bacterial contamination of four dental materials. Materials and Methods: In this analytic-descriptive study, flour of pumice, zinc oxide powder, prophylaxis paste and wooden wedges of available commercial brands were tested. To assure an examiner-blind study, the samples were coded in the microbiology laboratory. In sterile conditions, the samples were inoculated in tryptycase soy broth and sodium tioglycolate for aerobic and anaerobic bacterial growth, respectively. The media was then incubated in 35 degrees centigrade and checked daily. Results: Flour of pumice showed contamination to coagulase-negative staphylococci, enterococcus faecallis, bacillus and diphteroid. Some of the prophylaxis pastes were contaminated with micrococcus roseous, coagulase-negative staphylococci and diphteroid. One brand of wooden wedges demonstrated contamination to staphylococcus, diphteroid and bacilli. Zinc oxide powders were not contaminated. None of the samples showed contamination to anaerobic bacteria. Conclusion: Some of the investigated materials showed bacterial contamination, but the identified bacteria are not pathogen in normal situations. Key words: Bacterial contamination - Flour of pumice - Zinc oxide - Prophylaxis paste - Wooden wedge | 
