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4 things you NEED to know about waterline disinfection


Contaminated waterlines are a frightening proposition, but they're easily mitigated with these proactive steps.

It’s easy to take something as omnipresent as water for granted, but clean as it may look, danger can lurk just under the surface. Without proper cleaning and disinfection, microorganisms can collect in the dental unit waterline forming biofilm - a layer of microorganisms or bacteria - that can become dislodged and enter the water stream. If that happens, then really bad things can transpire.

For instance, consider infections that occurred at two separate children’s dental clinics - Georgia in 2015 and California in 2016. Both cases caused Mycobacterium abscessus infections in dozens of children. Fortunately such outbreaks are rare, but there are a few things dental practices can do to keep themselves - and their patients - safe.

Read more: How clean are the dental unit waterlines in your office?

The importance of testing

A key component of any waterline safety program is regular testing.

“Dirty waterlines and clean waterlines, unfortunately, look exactly alike,” says Peggy Spitzer, a dental hygienist and clinical education manager for Certol International. “We cannot see inside the tubing, we cannot see the biofilm forming.”

“I don’t think many offices are aware they need waterline disinfection,” adds Karen Daw, an infection control consultant and former clinic health and safety director for The Ohio State University College of Dentistry. “This is why water should be tested. I understand why many assume if the water is distilled or comes from a treated public water source then it must be safe, right? However, water travels into units, some with warmers (bacteria love warm water, by the way), then through very narrow tubing before it exits the handpiece or air/water syringe. And water sits in those lines, sometimes overnight, sometimes over the weekend or even a holiday break. Add low flow rate and voila: You have bacteria soup. Let that sit long enough and you could end up with harmful biofilm.”

How to test

While testing is critical, there’s no regulatory guideline on when or how to do it. Rather, it’s placed in the hands of manufacturers to ensure their specific equipment meets safety guidelines.

“How do you know if you are delivering water of acceptable quality unless you monitor?” asks Dr. Marie Fluent, DDS, former educational consultant for the Organization for Safety, Asepsis and Prevention (OSAP). “And that’s a big question. Since the CDC does not provide the specific recommendations for monitoring your water, clinicians must rely on the manufacturer of the dental unit and the manufacturer of the waterline maintenance products for recommendations. However, unless you test your dental unit water, how do you know if you have a problem?”

There are two main ways of testing dental unit waterlines: an in-office testing kit and a mail-in service.

“There are advantages and disadvantages to both,” Dr. Fluent says. “With an in-office variety, the results are available more quickly because it’s done in your own facility immediately after acquiring the water sample. However, the in-office tests may be a little bit less accurate than the mail-in variety. There is evidence to suggest the in-office methods underestimate water contamination, and this may be due to several factors: variations in room temperature and a lack of neutralization (or stabilization powder) in the test sample. The powder stabilizes the bacteria present in the test tube. Thus, when filling the test tubes, it is important to fill slowly and carefully to maintain the powder.”

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“Whatever product is being used to maintain the waterlines, follow the manufacturer’s instructions for use (IFU) on whether testing is recommended,” Daw adds. “Once tested, follow the manufacturer’s recommendations for frequency of testing to ensure the water remains at the EPA recommendation for safe levels of heterotrophic bacteria, or 500 CFU/mL (colony forming units per milliliter). Testing can be done in-house or via a mail-in service. In-office water testing is great for immediate pass-fail test results. A mail-in service provides the practice with third-party verification.”

There are no specific recommendations on when to use one method versus the other.

“We are sort of in the infancy of dental unit waterline testing, maintenance and monitoring,” Dr. Fluent says. “As years pass by, more detailed recommendations will most likely be provided. At this point in time, either testing method is appropriate. But as time goes on, I believe we are going to see more detailed recommendations, and possibly regulations, for dental unit waterline testing.”

Another consideration is where the water is tested. If a problem is discovered, how does the practice know whether the contaminated water originates within the dental unit or at the water’s source?

“Water should be tested coming out of your dental unit (air water syringe, handpieces, scalers and any other devices attached to water) as well as the source water,” Dr. Fluent says. “And that will help you determine, if there is contamination, where it does occur.”

“Test kits are available and not too hard to use,” Spitzer adds. “They need to be used at baseline (starting point) before any treatments and on a regular basis thereafter to confirm treatment is working.”

Up next: Shocking the system


Shock the system

Maintaining waterlines requires regular chemical treatment, including an occasional shock. How often a shock is performed depends on the practice and its equipment.

“Remember when dental water made the news two years running?” Daw asks. “Several children in two separate clinics had infections caused by Mycobacterium abscessus. The source of bacteria was untreated DUWLs with biofilm. So, what to do if the office is using a waterline disinfection product and tests only to discover they have high levels of bacteria? The office may want to implement a more aggressive treatment. Similar to shocking a pool, many manufacturers recommend shocking units upon installation and periodic shocking to remove bacteria and biofilm. This then brings the bacteria to levels the disinfection product can then help to maintain or eliminate.”

More from the author: 5 do's and don'ts of sterilization in the dental practice

The government leaves treatment requirements and specifications in the hands of waterline manufacturers.

“The CDC states that the dental unit manufacturer will recommend appropriate methods for equipment to maintain the quality of the water, so always check with the manufacturer of your dental unit for recommended products to shock and maintain waterlines” Dr. Fluent says. “In addition, the CDC recommends that the waterlines be flushed at the beginning and at the end of the day and between patients. Flushing is recommended to remove contaminated fluids because they become stagnant, and to remove potential retraction of patient-derived contaminants. Keep in mind that flushing alone will not guarantee the delivery of safe water. Some type of product must be used to prevent the buildup of biofilm and to expel existing biofilm.”

Available treatments

Manufacturers offer several different ways to treat dental unit waterlines. Dr. Fluent explains the different methods:

  • Tablets – “These are used alone on a daily basis to keep microbial levels low.”

  • Tablet used in conjunction with a separate shocking treatment – “This shock expels the existing biofilm and the tablet prevents buildup of microorganisms.”

  • Straws and cartridges – “They can be used in independent water reservoirs in the dental waterline unit. These straws and cartridges administer a small amount of antimicrobial agent on a continuous basis to prevent microbial buildup.”

  • Shock treatments only

  • Central treatments – “A waterline system that dispenses a certain quality of water.”

  • Daily liquid – “This is a product that you would put into your water reservoir on a regular (daily) basis.”

“These various treatment types are available by many manufacturers and numerous product choices are available.” Dr. Fluent says. “Clinicians should consult with the manufacturer of their dental unit and evaluate the pros and cons of each of these product choices to determine which type of product would be best for their dental unit and their situation. Whichever product your facility decides to utilize, it is important to follow the manufacturer’s instructions precisely. Any deviation in instructions may affect the success of the product.

Related reading: Is your practice safe?

“Some products require that they be used each time the water bottle is changed,” Daw adds. “Other products only need to be changed annually. Some products require a separate shock, while others have it built in. The best product is one that the team will remember to use properly. If it requires multiple steps, it’s possible one of those steps might get skipped. And if the instructions are numerous, it will need to be explained clearly to the person who is responsible for using the product. Using a product incorrectly, or forgetting to use it all, can mean unsafe water.”

Waterline testing and maintenance is becoming an important enough topic that - while not directly regulating it - agencies and organizations are taking an active interest in the issue.

“The FDA now has an area on its website dedicated to the maintenance of dental unit waterlines,” Dr. Fluent says. “The CDC also has information on dental unit waterlines as does the American Dental Association. The Organization for Safety, Asepsis and Prevention (OSAP) is currently working on a white paper that will provide its position and recommendations. This paper has not yet been finalized, so stay tuned for more information.”

While contaminated waterlines are a frightening proposition, like many other infection control concerns, it’s easily mitigated with proactive procedures. Practices should stay on top of testing and maintenance to ensure patient safety.

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