Microbial contamination of dental unit waterlines: origins and characteristics

Microbial adherence to the internal surface of dental tubing and the formation of a highly protective biofilm layer is predictable, given the ideal growth conditions in the tubing. The slime layer is the most common cause of dental water contamination. Various environmental and human-derived potential pathogens have been reported worldwide. Dental equipment such as retracting shut-off valves, antiretracting valves that tend to fail, or waterlines that are inaccessible contribute to a situation in which virtually every standard dental unit contains contaminated water. While exposure to Pseudomonas, Moraxella, Staphylococcus, and Legionella has been linked to dental water, the medical risk of dental unit waterline contamination is most significant to immune-deficient individuals. Regulations and technological devices are emerging to manage dental water quality.