Quality of dental unit water at university dental clinic, private and public clinics in Tromsø. Investigation of bacteria levels in water samples in dental chair water lines

Abstract

Abstract: Exposure to water with high bacterial counts violates the basic principles of clinical infection control in dental clinics. Therefore, bacterial counts in water that comes from the dental chair unit should always be evaluated. As guideline water that comes from hand pieces/three-way syringes should have less than 200 colony forming units per one mL of water.

Aims: The aim of this study is to investigate levels of bacteria in dental unit water at University Dental Clinic (UDC), public and private clinics in Tromsø, and assess the hygiene procedures for dental unit water at the different clinics.

Materials and methods: Water samples from dental chair at UDC, public and private clinics were obtained for microbiological analysis. Water samples were cultivated in agar plates and in prefabricated sample kits to investigate the growth of bacteria. Digital droplet PCR (ddPCR) was used to evaluate the bacterial load in these samples.

Results: Differences in the amount of bacteria in water samples between UDC, private and public clinics were detected. UDC had lower bacterial load in the dental unit water than the private and the public clinics. There was a significant difference in level of E.coli counts, Heterotrophic plates counts (HPC) and the ddPCR counts between the UDC and the other two groups. There was also a significant difference between the private and the public clinics, in level of bacteria determined by the ddPCR. The public clinics had the highest level of bacteria in the water from the dental chair units.

Conclusion: It seems that water coming from the dental chairs at UDC have the lowest bacterial load than the water obtained from the dental chairs at public and private clinics. The reason of high bacterial loads in the private and public clinics could be suboptimal infection control measures in these places. In addition, high bacterial load could be attributed to old pipe system and lack of stringent water filtration system within the clinics. Even though the study has shown high levels of bacterial load we cannot conclude that dental unit water is considered to be a risk for immunocompromised patients. This is because of, no attempt has been done to identify, what kind of bacteria that are present in the water and if these bacteria are pathogenic or not.