Dental unit water systems (DUWS) harbor bacterial biofilms, which are known reservoirs for pathogens.1 In 1995, the ADA Council on Scientific Affairs responded to scientific evidence that suggested the microbiologic quality of water used in dental treatment required improvement.2 A call to action was taken on the design of dental equipment. By the year 2000, water used during nonsurgical dental procedures consistently contained no more than 200 colony-forming units per milliliter (CFU/mL) of aerobic mesophilic heterotrophic bacteria in the unfiltered output of the dental unit. A heterotroph is “an organism that cannot fix carbon from inorganic sources (such as carbon dioxide) but uses organic carbon for growth.” https://en.wikipedia.org/wiki/Heterotroph These bacteria are not necessarily harmful, but determining the heterotrophic plate count is used as an indication of the amount of residual disinfectant present in a water supply. Since then, technological advances have made this possible. The Centers for Disease Control and Prevention (CDC) now recommends that “coolant water used in nonsurgical dental procedures meet EPA regulatory standards for drinking water,” which is less than or equal to 500 CFU of heterotrophic bacteria per milliliter of water. This recommendation was published in the CDC’s Guidelines for Infection Control in Dental Health-Care Settings—2003. (Guidelines from the CDC differ about water used in oral surgical procedures.)
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