Detection of Bacterial Contamination in Dental Unit Water Lines and Testing the Effectiveness of Disinfectants against these Contaminants

Aim: Contaminated dental unit water lines (DUWLs) are a possible source for spreading microorganisms in dental practices. The aim of this study was to detect the bacterial contamination of dental unit water and investigate the effectiveness of the disinfectants.

Methodology: Bacterial contamination was detected by a) using bacterial culture of heterotrophic bacteria, total coliforms and Pseudomonas aeruginosa and b) Scanning electron microscopy (SEM) of DUWLs tube. Subsequently, dentists were suggested to treat the DUWLs with disinfectants to eradicate bacterial contaminants and its effectiveness was tested after three months.

Results: Bacterial contamination of the water samples ranged from not detected to 2.38×106 CFU/mL. Out of 34 DUWLs water samples tested, 30 (88.24%) samples exceeded the Centers for Disease Control and Prevention (CDC) and Environmental Protection Agency (EPA) recommended threshold of ≤500 CFU /mL, whereas only 4 (11.76%) samples met the standards. Contamination by total coliforms and P. aeruginosa was detected in 52.94% and 64.7% of samples respectively. SEM displayed a dense biofilm on DUWLs tubing confirming the bacterial contamination. The intervention for disinfection of DUWLs resulted more than 50% samples with acceptable bacterial count in test performed after three months.

Conclusion: The high rate of bacterial contamination of dental unit water highlights the need to disinfect and monitor the quality of DUWLs periodically.