The presence of Pseudomonas aeruginosa in the dental unit waterline systems of teaching clinics

Objective: The objective of this study was to evaluate the extent of Pseudomonas aeruginosa contamination of Dental Unit Water (DUW) at a Dental Teaching Center in Jordan. Methods: Water samples were collected from 30 dental units, 10 from each of three teaching clinics, namely conservative dentistry, periodontology, and prosthodontics. Samples were collected from the outlet of the air/water syringe, high-speed handpiece and water cup filler, at the beginning of the working day (before use), after 2 min flushing, and at midday. Results: P. aeruginosa was detected in 86.7% (26/30) of the dental units at the beginning of the working day, and in 73.3% (22/30) after 2 min of flushing and at midday. Conservative dentistry units had the highest counts, followed by periodontology and prosthodontics (P< 0.05). Overall, the highest counts (log 10 count CFU ml -1 ) were at the beginning of the working day (1.38 ± 1.05), and the lowest counts after flushing for 2 min (1.10 ± 1.03), and higher numbers were seen again at midday (1.15 ± 1.04) (P < 0.05). Conclusions: 86.7% of the dental units were contaminated with P. aeruginosa, the conservative dentistry units had the highest amount of contamination. Flushing the DUW for 2 min significantly reduced the counts of P. aeruginosa.