It is presumed by most people, even those who work in the industry, that there are no concerns around water quality in dental surgeries. Sadly, this is far from the reality. It is fact that, from a microbiological perspective, the dirtiest part of a dental surgery is the water lines in the chair itself.

Dental Unit Water Lines (DUWL) is the term given to the small flexible tubes that are built in to the dental chair. These are a perfect havens for microorganisms. The water is warm, slow moving and flows through very small diameter lines, which offer a larger surface area, proportional to volume. This allows for rapid build up of biofilm.

In 1952, the American army established a standard in which the number of colony forming units must be less than 500, i.e., 500 bacteria per ml of water. To this day, most countries in the civilised world, including Australia recognise this safe limit. One exception incidentaly, is Japan, with an acceptable standard of just 100 CFU/ml.

Due to the added risk of infection during treatment, the American Dental Association (ADA) has set the microbial level for water coming from DUWL to be <200 CFU/ml.

The Australian Dental Association tends to sit somewhere in the middle, as their ‘Guidelines for Infection control’ state: ‘The number of bacteria in water used as a coolant/irrigant for non-surgical dental procedures should be less than 500 CFU/mL, since this is a widely used international limit for safe drinking water. When treating immunocompromised patients, it is recommended that water from dental unit waterlines contain less than 200 CFU/mL.’

Many papers from the research community show that bacterial levels in the majority of tests on DUWL water far exceed these allowable levels. Göksay, Çotuk, Zeybek1 note: “We have determined that only 2 (3.4%) out of 59 dental unit water samples were found to meet the standard.”

Indeed, intendant research by Bion Systems has found that no DUWL tested by the company in Australia, met either the ADA standard, or even the standard for potable water as laid down in the ‘Australian Drinking Water Guidelines”, of 500 CFU/ml.  The lowest reading recorded in this research was 3,100 CFU/ml, or nearly 16 times the ADA standard. The highest reading recorded was 150,000 CFU/ml. Göksay, Çotuk, Zeybek1 recorded a reading of 3,330,000 CFU/ml, a level one would expect to find in sewerage effluent.

One study found biofilm present in the lines of a brand new, unused chair2, whilst another study has shown that microbial levels in dental unit water reached 200,000 CFU/mL within just five days after installing new dental unit waterlines.3

Does this evidence point to a problem though? Yes, it does. There are a plethora of studies and media reports of dentists, staff and patients becoming ill, or worse dying from pathogens linked to DUWL.

One study identified the same Pseudomonas species both in dental units and in the nasal flora of 14 of 30 dentists evaluated4, whilst other studies indicate that dental personnel have higher exposure rates to Legionella species than non-dental populations used as control groups in the investigations5,6.

From a patients perspective, the risk of contracting disease and infection is also very real. In 2012, an 82 year old Italian woman died from legionnaires disease contracted from her dentist7. Genome testing proved that the legionella in the woman’s lungs was identical to the bacteria taken from the water lines of the dental surgery.

Possibly even more disturbing, is two separate clusters of Mycobacterium infections reported in the United States. In September 2015, nine children were confirmed to have contracted an infection whilst undergoing dental procedures in Georgia8. In September of 2016, a number of cases were reported, stemming from a public health clinic in Anaheim, Calafornia9. Dr. Eric Handler, health officer with the Orange County Health Authority explained: “The reason we’re so concerned is this infection is very hard to treat with antibiotics, instead, the tissue is surgically removed. Treatment can be very traumatic and deforming.” One child had 4 teeth and part of her jawbone removed. As of July 6, 2017, there were 73 cases, 72 requiring hospitalisation10.

The question is:  So what can be done about pathogens and biofilm formation in Dental Unit Water Lines?

Bion Systems have developed an AccuionTM copper-silver unit, specifically for the dental industry. These units have been successfully installed in dental and orthodontic surgeries around Australia and shown to reduce microbiological loads in DUWL to safe levels.

Contact us for more information


  1. Duygu Göksay, Ayşın Çotuk Zuhal Zeybek. Microbial contamination of dental unit waterlines in Istanbul, Turkey Environmental Monitoring and Assessment Volume 147, Issue 1–3, pp 265–269
  2. Tullner JB, Miller CH, Sheldrake MA, Gonzalez-Cabezas C. Accumulation of biofilm inside of dental unit waterlines. Annual Conference Proceedings, Organization for Safety and Asepsis Procedures, 1996; abstract #9602.
  3. Altas RM, Williams JF, Huntington MK. Legionella contamination of dental unit waters. Appl Environ Microbiol 1995;61:1203-13.
  4. Clark A. Bacterial colonization of dental units and the nasal flora of dental personnel. Proc R Soc Med 1974;67:1269-70.
  5. Fotos PG, Westfal HN, Snyder LS, et al. Prevalence of Legionella-specific IgG and IgM antibody in a dental clinic population. J Dent Res 1985;64(12):1382-5.
  6. Reinthaler FF, Mascher F, Stunzner D. Serological examinations for antibodies against Legionella species in dental personnel. J Dent Res 1988;67(6):942-3.
  7. Carollo K. ABC News. February 17, 2012. Accessed April 10, 2018
  8. Peralta G, Tobin-D’Angelo M, Parham A, et al. Notes from the Field. Mycobacterium abscessus Infections Among Patients of a Pediatric Dentistry Practice — Georgia, 2015. MMWR Morb Mortal Wkly Rep 2016;65:355–356. DOI:
  9. Ross E. NPR September 30, 2016. Accessed April 10, 2018
  10. OC Health Care Agency July 6, 2017. Accessed April 10, 2018