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MICROBIAL CONTAMINATION IN DENTAL UNIT WARM WATER SYSTEMS,
NAVAL DENTAL SCHOOL BETHESDA MD
Pagination or Media Count:
Aerosols can be created and disseminated by high speed rotary instruments using water from the warm water system of dental units. If these aerosols contain appreciable quantities of microorganisms, this may introduce a danger of airborne infection into the dental operating room. The purpose of this study was to determine the presence of microbial contamination in dental unit warm water systems and to ascertain the level, extent, and persistence of this contamination. The warm water systems of 44 dental units at three naval facilities and one U.S. Public Health Service facility were sampled and tested for the presence of microorganisms. All were found to be contaminated with 4000 or more colony-forming units cfu per ml, with a mean recovery of 631,000 cfu per ml. These microorganisms were essentially flavobacteria, pseudomonas, and other gram-negative bacilli. Flushing water through the drinking cup warm water dispenser, air turbine handpiece line, and warm water syringe of each unit for 2 minutes at approximately 1,500 ml per minute reduced the concentration of microorganisms to less than 10 cfu per ml in most units. Persistently contaminated units required flushing times up to 30 minutes. It was concluded that the warm water system of dental units is a focal source of microbial contamination and that until effective sterilization procedures are developed all dental units should be flushed for at least 2 minutes prior to daily use. Author
APPROVED FOR PUBLIC RELEASE