Abstract
Studies conducted over the last 40 years have demonstrated that the water output from dental unit waterlines (DUWLs) is often contaminated with high densities of microorganisms. It has been monitored the microbiological quality of the water in 30 public dental facilities in northern Italy in order to assess the health risk for patients and dental staff. In each facility, samples of water both from taps and from DUWLs were analyzed in order to evaluate heterotrophic plate counts (HPCs) at 22 °C and 36 °C, and to detect coliform bacteria, Pseudomonas aeruginosa, Legionella pneumophila and amoebae. In 100% of the samples taken from the DUWLs, the concentration of HPCs was above the threshold as determined by the Ministère de la Santé et des Solidarités (2007). The concentration of P. aeruginosa was greater than the indicated threshold in 16.67% of the hand-pieces analyzed. A total of 78.33% of samples were contaminated by L. pneumophila, while in the samples taken from the DUWLs alone, this percentage rose to 86.67%. Amoebae were detected in 60% of the samples taken from hand-pieces; all belonging to the species V. vermiformis. This study documented the presence of various microorganisms, including Legionella spp., at considerably higher concentrations in water samples from DUWLs than in samples of tap water in the same facilities, confirming the role of the internal DUWLs in increasing microbial contamination, especially in the absence of proper management of waterborne health risks.
Highlights
Studies conducted over the last 40 years have revealed that the water output from dental unit waterlines (DUWLs) is often contaminated with high densities of microorganisms; [1,2] such contamination may be caused by the water supply itself, or, more probably, by the suck-back of biological fluids from the oral cavities of patients [3,4]
The guidelines issued by the Centers for Disease Control and Prevention (CDC) on infection control in dental health care settings recommend that level of heterotrophic plate counts (HPCs) in dental unit output water should not exceed 500 colony-forming units (CFU)/mL [2]
Data from the present study suggest the presence of considerable contamination in DUWLs that could be a source of hazards, for dental patients and for healthcare personnel, who are routinely exposed to the same risk [9]
Summary
Contamination levels ranging from 102 to 108 colony-forming units (CFU)/mL have regularly been reported [1,4,5]. These counts can occur because the features of dental unit waterlines (e.g., flow rates, materials and system design) promote both bacterial growth and the development of biofilm [2], which protects the organisms from desiccation, chemical aggression and predation [6]. Public Health 2019, 16, 2648; doi:10.3390/ijerph16152648 www.mdpi.com/journal/ijerph
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