CODHA Explorer January 2023

Michelle Strange, MSDH, RDH

Picture this… you are finishing up with a patient in your clinic. They sit up, remove their glasses, and you tell them it’s time to rinse. You grab a cup and run to the bathroom, filling it with water from the toilet bowl before presenting it to your patient. 

Are you grossed out yet? You shouldn’t be. Because unfortunately, in many cases, your clinic toilet water is safer and cleaner than what’s coming out of your dental water unit!

A little while ago, I tested the dental water unit lines in a clinic against water from the clinic’s toilet, and guess which came back looking more hygienic? Yup, the toilet water. Shocking, I know.

There must be something in the water!
Dirty dental water is not a new concern. While infection control has come a long way in recent years, for some reason, this area is repeatedly overlooked. Many studies have found that dental water lines are extensively contaminated with microbial biofilms,1  and pathogens of at least 40 different species have been found, including non-tuberculosis Mycobacterium, Streptococci, and Legionella. 

These bacteria, which are being sprayed directly into our patients’ mouths during dental procedures, can cause severe illness, particularly in our elderly and immunocompromised patients. So, where is it coming from? 

While the microorganisms likely come from the source water or the patient’s saliva, the low flow rates in the dental unit waterlines (DUWL), coupled with frequent periods of stagnation, allow pathogens the perfect environment to replicate.2

Out of sight, out of mind!
The cleanliness of dental unit water lines is so often overlooked, and we have to ask ourselves why that is when they are so capable of spreading disease to our clients. Unfortunately, the microorganisms that are found in the water are not visible to the human eye. Even if the water is running clear, bacteria could still lurk unseen. Dirty waterlines and clean waterlines can look the same. 

Furthermore, many clinics use distilled water for their units and assume that this means their water is safe. This makes it even more critical to implement water testing protocols, but there have yet to be regulatory guidelines on how or when to do that.3

Test your water, treat your water, and shock your lines!
During a public health investigation, the water of seven dental stations was found to contain bacterial counts over the 500 colony-forming units recommended by the CDC. In fact, a whopping 91,333 CFU/mL was recorded as the average.4  

At a conference hosted by OSAP, leading dental infection control experts stated that “dental unit waterlines” are the most pressing infection control issue facing dentistry over the next five years.5  Thankfully, OSAP has now developed guidelines and general recommendations for practitioners to help address this. 

These include recommendations to stay up to date with current information regarding the control of biofilm contamination, to regularly review instructions for the use of the dental water unit, to flush waterlines for 20-30 seconds between patients, and to monitor dental unit water quality frequently.6

The importance of an ICC!
Of course, with DUWL hygiene not being something that falls within the day-to-day operating procedure of many clinics, it is vitally important that they have a standard operating procedure (SOP) of their own. It is also crucial that all staff members are educated on the importance of managing dental water quality and be trained to comply with the SOPs.

Appointing an infection control coordinator to do this is essential for the safety of patients and staff alike. It will help avoid very preventable waterborne diseases being spread in the clinic. 

Some action items that the ICC could implement based on the OSAP guidelines include;

  • Reviewing and understanding the instructions for the use of the dental unit
  • Testing waterlines monthly
  • Shocking waterlines with a strong disinfecting agent
  • The precise documentation of all procedures and tests to prove infection control compliance
  • Not relying on reverse osmosis units and distillers to limit the growth of bacterial colonies
  • Using sterile water for surgical procedures

Having an ICC is imperative for creating a safety culture in any practice.7  After all, if not everyone is on board and there is no one to oversee the implementation of safety procedures correctly, then it is highly likely that the ‘out of sight, out of mind’ mentality will continue.  

It is time that we all clean up our act regarding patient safety, and by having a trusted ICC working in our clinics and ensuring our waterlines are safe, we can remove some of the risk factors that may cause serious harm.

Michelle Strange, MSDH, RDH CDIPC, is an authorized OSHA Trainer and compliance consultant.
Michelle has been a clinician in dentistry since 2000 and is currently a practicing hygienist, speaker, writer, owner of MichelleStrangeRDH and Level Up Infection Prevention Podcast.
Find out more about Michelle at or


1 “Breaking the Chain of Infection: Dental Unit Water Quality Control.” Accessed 1 Dec. 2022.
2 Dental Unit Waterlines (DUWL) –” Accessed 1 Dec. 2022.
3 “4 things you NEED to know about waterline disinfection.” 27 Aug. 2018, Accessed 1 Dec. 2022.
4 “Invasive Mycobacterium abscessus Outbreak at a Pediatric Dental ….” Accessed 1 Dec. 2022.
5 “The Importance of OSAP’s New Dental Water Quality ….” 24 Oct. 2022, Accessed 1 Dec. 2022.
6 “Journal of Dental Infection Control and Safety.” Accessed 1 Dec. 2022.
7 “How To Prevent Infection Control Breaches with an ICC | igniteDDS.” Accessed 1 Dec. 2022