Microbial water quality management of dental unit water lines at a dental school.

Contaminated dental unit water lines (DUWLs) are a possible source for spreading micro-organisms in dental practices. This study reports the microbial load of the water from DUWLs of a large dental school over time. The water quality of 231 dental chairs was tested three times over 1.5 years; 175 DUWLs at student clinics and 56 DUWLs at staff clinics. DUWLs at the staff clinics met the Dutch requirement of 100 colony-forming units/mL. An increasing number of DUWLs at the student clinics complied with this requirement, indicating that the local protocols are adequate but that compliance can be improved.