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Dental Water: The Dirty Little Secret

July 1, 2006
Just as biofilms form rapidly on teeth, they also colonize rapidly inside dental unit waterline (DUWL) tubing.
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Just as biofilms form rapidly on teeth, they also colonize rapidly inside dental unit waterline (DUWL) tubing. I observed this problem firsthand several years ago in a dental hygiene clinic where DUWLs were not purged, flushed, or disinfected. With water syringe in hand, I emptied some of this water into a plastic cup. Lo and behold, there were brown, stringy, slimy biofilms in the cup. I was completely grossed out, to say the least!

The majority of organisms in biofilms are harmless environmental species, but some dental units harbor respiratory pathogens that can be harmful to patients and clinicians. There is plenty of scientific evidence that water used routinely as a coolant and irrigator is heavily contaminated with biofilm-containing microorganisms, and these slimy substances live on the walls of small-bore tubing.

DUWL tubing is typically 1/8” or 1/16” in diameter, which creates a high surface area to volume ratio. In other words, a higher percentage of water comes in contact with the tubing than it would in a tube with a larger diameter. Visualize the brown, stringy, slimy biofilms being expressed into a patient’s mouth and aerosolized into the operatory. The water is of poor microbiological quality and would most likely fail U.S. drinking water standards.1

During January, when the Atlanta sky where I live was gray and gloomy, I registered for an OSAP dental infection-control course in the city’s midtown area. For those of you who are unfamiliar with OSAP, it stands for the Organization for Safety and Asepsis Procedures (, which is dedicated to promoting infection control and safety practices supported by science and research.

Of the many topics discussed during the four-day conference, dental unit waterlines was the one I knew the least about. I learned rather quickly that bugs love stagnant water, and we seem to have plenty of that in our operatories! Does anyone remember ABC’s “20/20” television report in August 2000 that focused on dental water? I remember the shocking statistics that showed water samples containing a myriad of bacteria were considered safe under federal drinking standards. The message was that dental unit water has the “potential” to be dangerous, especially with the “suck back” from air/water syringes.

In 2003, the Centers for Disease Control and Prevention (CDC) issued guidelines for infection control in dental care settings, and most hygienists have read this important document. If not, go to Pay close attention to the dental unit waterline section that recommends using water that meets the Environmental Protection Agency’s (EPA) regulatory standards for drinking water, which is <500 CFU/mL. What does CFU/mL stand for? CFU refers to colony-forming units, and is a scientific term that is a measure of the growth or density (total amount) of bacterial colonies. Click here to view Synopsis of Dental Unit Waterline Treatment Products and Devices

Who is at risk for contamination?

According to the CDC, individuals with HIV/AIDS, diabetes, transplant recipients, chemotherapy patients, and those with a weakened immune system may be more susceptible to microbial contaminants in drinking water.2 Under certain conditions, some patients even need to boil their drinking water.2 This risk is worsening due to increasing numbers of immunocompromised patients and dental personnel with weakened immune systems who have potential for contamination through aerosol mists.

Here’s the confusing part about selecting treatment protocols, devices, and products that will help you attain this CDC goal. There are two ways to purify dental unit water: a continuous delivery system or an intermittent system in which a solution is delivered to the waterlines on a scheduled basis. What’s so confusing about this? There are many products on the market that accomplish this task, but costs are different. Also, some products involve daily, weekly, or monthly maintenance that can be forgotten or left incomplete. Ease of use is an important issue, and some products are registered with the FDA/EPA while others are not.

According to OSAP, there is no universally accepted dental water treatment product or protocol to ensure EPA requirements for purity in dental unit water.3 Factors to consider when selecting a system include initial and annual cost, ease of use, registration by the EPA or other governmental agency, compatibility with dental equipment and materials, and patient safety issues.3 Don’t listen to rumors about incompatibility of waterline disinfectants with dental bonding agents until you talk to a company representative.

Some waterline products have FDA/EPA clearance to enter the market and some do not. In general, products that are solutions are handled and cleared by the EPA because they are classified as pesticides, whereas products that attach to dental units and make biological claims go through the FDA for clearance to the marketplace.

The California Department of Pesticide Regulation has mandated that all waterline cleaners sold into the state must be registered not only with the State of California EPA, but also the Federal Government EPA. This decision has resulted in at least one product being withdrawn from the California market voluntarily, and all of the other waterline cleaners/pesticides being placed on hold until registered with the state agency.4

When I visited OSAP, I had an opportunity to stroll around the exhibit hall and meet about a half dozen sales representatives from companies that market and sell these products. My general impression after meeting several of them was that there are many effective, safe, and economical systems. There are many questions that you, as an oral health-care professional, need to ask salespeople. Here are a few suggestions:

Is this product cleared by the FDA or EPA? This tells you that the company’s claims have been reviewed. Ask for the registration number. If they can’t or won’t tell you, go to the FDA and EPA Web sites at and, and type the company name in the search bar. If the information is not provided, be forewarned as to the veracity of their claims.
What is in your product? Is it safe for patients, staff, and equipment? Again, ask for written documentation.
What is the annual cost to use? Remember, this is very different from cost to purchase.
Ask for references such as dental schools, hygiene schools, and military clinics. Ask other offices what they use and why.

Table 1 shows the various DUWL products and devices that were evaluated by the U.S. Air Force Dental Evaluation and Consultation Service (DECS). This list was presented to participants at the OSAP course I attended and is printed in an abbreviated version here for RDH readers. In addition to reading Table 1, please visit DECS provides a detailed evaluation of each product which can be read online.

A water bottle disinfection system is useful only if all of the units in the dental practice are fitted with water bottles. If done correctly, the water bottles must be filled each day, cleaned each week, and taken off the unit every night, and every line must be purged at each chair each night. Also, the bottle threads, once stripped, need to be replaced, and the labor on bottle threads can be expensive.

In addition, compliance with water bottle instructions is difficult to monitor, and it’s likely that team members will not always comply with daily and weekly instructions. Many bottle systems are safe and economical and many reputable companies sell them, but make sure to calculate the cost of maintaining the bottle system when making your final decision.

Whatever treatment option you choose, remember that doing nothing or placing an antimicrobial in your water bottle is likely inconsistent with EPA regulatory standards for drinking water. Regardless of whether or not your state mandates compliance with CDC infection-control guidelines, failure to keep patient treatment water at or below the EPA drinking water limit of 500 cfu’s is failure to meet the standard of care.

Soon, one of your patients will ask about your water disinfection protocol, and you will want to proudly tell him or her exactly which system you use. I also predict that in the future, dental practices will post signs in the reception area announcing compliance with EPA regulatory standards for dental treatment output water. As with other safety and infection-control issues, dental hygienists can take the lead and stand proud.


1 DePaola LG, et al: A review of the science regarding dental unit waterlines. JADA 2002; 133:1199-1206.
2 Centers for Disease Control and Prevention: Guidelines for infection control in dental health-care settings 2003. MMWR, Dec. 19, 2003; 52 (RR-17).
3 OSAP (Organization for Safety and Asepsis Procedures): Practice tip. Infection Control In Practice Jan. 2006; 5(1).
4 Insider eJournal: California criticizes EPA’s enforcement response to biofilm products Jan. 31, 2006; 3(2).