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 com­posed 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 dent-al 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 ×10 5 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. KEY WORDS: Dental unit; Water line; Bacterial contamination; Flushing