Detection and Quantification of Bacterial Flora in Dental Unit Water Systems and the Effect of Flushing on its Reduction

Statement of Problem: The origin of Dental Unit Water Lines (DUWL) contamination is specially related to the formation of biofilm which is com posed of microorganisms within water and is located on the tubing lines. Purpose: In this descriptive study, we evaluated the degree of contamination with Gram positive and Gram negative bacteria in DUWLs of the dental school and also determined the efficacy of flushing on reducing its microbial count. Materials and Methods: Thirty dental units from all the departments of dental school in Tehran University of Medical Sciences were selected for this study. Sampling consisted of a two step procedure before and after one minute of flushing. The samples were taken from air/water line of each selected dental unit separately. Air/water syringe of each unit was completely disinfected with Deconex before sampling. Results: The range of the contamination varied from190 to 23 ×105 CFU/ml. The bacterial contamination included anaerobic Gram negative bacilli, non-fermenting Gram negative bacteria, Gram positive cocci and Gram positive bacilli. In all the samples taken from water taps, contamination was noted, varying from 25 to 1700 CFU/ml. This was significantly lower than the contamination of air/water syringe of the dental units. Conclusion: Applying the right principles for infection control such as using disinfectants or sterile water in dental settings and daily flushing before visiting patients can be of great significance.