Overview—Dental Unit Water Quality

Drinking water must meet a certain standard with respect to concentrations of contaminants and chemicals.

The maximum concentration of heterotrophic bacteria set by the EPA, the American Public Health Association (APHA) and the American Water Works Association (AWWA) is 500 colony-forming units per milliliter (CFU/ml) of drinking water. The quality of water delivered by dental units will not meet this standard without regular maintenance.

In fact, research has shown that microbial counts can be as high as 200,000 CFU/ml within 5 days of installation of new dental unit waterlines; 1 and, without maintenance, levels as high as 10 6 CFU/ml of dental unit water have been found. 2,3 The small diameter of dental waterline tubing, combined with their design and flow rate, enable bacteria and other microorganisms to form a biofilm that coats the inside of the tubing. As the water travels through the waterlines the microorganisms slough off resulting in contamination of the water.

Although there is no evidence that dental unit water is harmful to patients 4 , the CDC has stated that, "Exposing patients or dental health care personnel to water of uncertain microbiological quality, despite the lack of documented adverse health effects, is inconsistent with generally accepted infection control principles."