ABSTRACT
Cross contamination via dental laboratories is an important problem. Among dental and laboratory procedures, two of the most important topics are disinfection of impressions and disinfection of prostheses. Because pumice slurry is widely used in final stages of polishing and finishing of prostheses, it should not be contaminated and if so, it could be a serious potential source of cross-infection. Therefore, this study was done to determine the incidence and also the type of pathogenic oral and non-oral microorganisms in polishing pumice of dental laboratories in the city of Shiraz. This study was a descriptive-analytical investigation. In the same controlled and sterilized condition, the used pumice samples were collected from 12 dental laboratories. Immediately, they were transported to microbiology section of standard institute and cultured in specific and non specific media. For isolation of different types of oral and non oral microorganisms, 16 different tests were applied. A wide range of microorganisms were isolated from all samples of dental pumices. Dominant bacteria in our study in order of frequency were: Acinetobacter lowffi, Bacillus cereus, Staphylococcus aureus, pseudomonas aeroginosa, diphtheroids, citrobacter frundi, enterobacter aerogenes, morganella morganii, clebsiella pneumonia, staphylococcus saprophyticus, streptococcus viridanse. 85.70% of the bacteria detected were non-oral microorganisms and 14.30% were oral microorganisms. This study showed that dental pumices are heavily contaminated with oral and especially with non-oral microorganisms and there was a high risk of cross-infection between clinician, patient and technician. Therefore infection control in all steps of prosthesis construction is recommended