Biofilms in Dental Unit Water Lines.

Biofilm formation has become a significant problem in dental unit water lines (DUWLs). The formation of biofilms and microbial growth in DUWLs leads to an unacceptably high number of microorganisms in the water used for spraying, cooling, and ultrasonication procedures. These procedures form aerosols which can be inhaled by the patients, and consequently dentistry constitutes an area of specific concern for patient safety. In particular, older and immunocompromised patients are at risk of serious respiratory tract infections if the water contains pathogens such as Legionella pneumophila and Pseudomonas spp. In the EU it is recommended that the water in DUWLs should not exceed 200 colony-forming units (CFU) of heterotrophic bacteria (bacteria living on organic material) per milliliter of water to be acceptable in dental work. A number of efficient products are available on the market that can be applied onto dental units. New dental units are nowadays equipped with "inbuilt" systems. Such measures have resulted in an acceptable standard of water in 95% of the 1,200 dental units in the Public Dental Health Service of the Västra Götalands region of Sweden that were followed yearly for 4 years. For the majority of the remaining DUWLs with an unacceptable standard this is due to neglect or inappropriate routines for water-cleaning procedures. It is the ability to follow instructions rather than the cleaning procedure itself that is decisive if clinics and dental units are to have an appropriate standard of water in their systems.