Evaluation of Bacterial Contamination Level of Waterlines in Dental Units in Dentistry School of Qom University of Medical Sciences in 2018

Background and Objectives: According to hazardous infection possibility in patients with a weakened immune system, old adults, and children, microbial contamination in the waterlines of dental units has become a recent concern. The aim of the present study was to evaluate the microbial contamination in dental unit waterlines in the School of Dentistry, Qom University of Medical Sciences, Qom, Iran.   Methods: This descriptive-analytical study investigated 94 water samples collected from three parts of each unit, including air/water syringe, turbine headpiece, and cup filler, in the School of Dentistry in 2019. The water samples were taken on Saturday and Wednesday before and 60 sec after flushing on the same unit. The samples were transported in closed sterile containers to the Microbiology Laboratory. All the samples were incubated on nutrient agar plates using the Spread plate technique. Subsequently, bacterial contaminations were counted and reported based on CFU/ml for every plate. The data were analyzed using the Kruskal-Wallis test and Wilcoxon signed-rank test by SPSS software version 25.   Results: The total mean of the bacterial counts was reported as 16,457 CFU/ml. The pre-clinic and periodontics were reported with the highest and lowest bacterial counts, respectively. The mean of bacterial counts after flushing was significantly lower than that reported before flushing on the same unit (P<0.001). The mean bacterial contamination of different parts of the dental units was similar (P=0.145). There was no statistically significant difference between the mean bacterial counts of Saturday and Wednesday (P=0.074).   Conclusion: The obtained results of this study demonstrated that the biological contamination level of dental unit waterlines is high, and flushing can result in a partial decrease in this regard.