Microbial Contamination of Pumice Powder and Slurry in Dental Laboratories of Hamadan

Background: Using contaminated pumice in polishing process of dental prostheses may result in cross-contamination of dentists, laboratory technicians, and patients. Objectives: This study aimed to determine the presence and level of microbial contaminants in pumice powder and slurry used in dental laboratories of Hamadan city. Materials and Methods: Forty specimens, including ۲۰ pumice powders and ۲۰ pumice slurries were collected from ۱۰ randomly selected dental laboratories and inoculated onto selective and non-selective media in order to count the total colony-forming units (CFU). Isolated fungi and bacteria were identified using Gram-stain and deferential diagnostic tests. Results: Results of this study showed ۸۵% contamination rate for pumice powders and ۱۰۰% for pumice slurries. Frequencies of Grampositive and Gram-negative bacteria isolated from the powders were ۶۸% and ۳۲% respectively. For the slurries the frequencies were ۶۱% Gram-positive and ۳۹% Gram-negative. Organisms detected in pumice powders composed of Staphylococcus epidermidis, E. coli, Acinetobacter, B. cereus, Enterobacter, Candida, and diphtheroids. Organisms detected in pumice slurries included Staphylococcus epidermidis, E. coli, Citrobacter, S. aureus, Enterobacter, B. cereus, B. proteus, Candida, and diphtheroids. Conclusions: According to this study, pumice powder and slurry used in dental laboratories of Hamadan are contaminated. Therefore, the Laboratory staff should be aware of the hazards posed by the presence of pathogens in dental laboratories