Contamination of dental unit water lines with Pseudomonas aeruginosa

Objective: This study evaluated the extent of Pseudomonas aeruginosa (P. aeruginosa) contamination in the Dental Unit Water (DUW) at a dental institution for three different specialty teaching clinics. Methods: Water samples from thirty dental units at the Dental Teaching Center of Jordan University of Science and Technology were investigated. Samples were collected from three teaching clinics, namely; conservative dentistry, periodontology and prosthodontics. The water samples were collected from the outlet of air/water syringe, high speed handpiece and water cup filler. Time of sampling was, at the beginning of the working day (before use), after 2 minutes flushing, and at mid day. Data was analyzed by Repeated Measures followed by Bonferroni test. Results: At the beginning of working day P. aeruginosa was detected in 86.7% (26/30) of the dental units, and in 73.3% (22/30) after 2 minutes of flushing and at mid day. The water samples of conservative dentistry clinic had the highest counts, followed by periodontology and prosthodontics (P<0.05). Overall, the highest P. aeruginosa counts (log10 count CFU/ml) were at the beginning of working day (1.38 ± 1.05), followed by reduced counts after flushing for 2 minutes (1.10 ± 1.03), and then became higher at mid day (1.15 ± 1.04) (P<0.05). Conclusion: 86.7% of the dental units were contaminated with P. aeruginosa, and the Conservative dentistry units had the highest contamination. Flushing the DUW for 2 minutes significantly reduced the counts of P. aeruginosa.