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Best practices for dental unit waterline management

July 10, 2023
Dental practices must keep a close eye on bacterial levels in dental unit waterlines. Melissa Van Witzenburg, RDH, explains the importance of the often-overlooked DUWLs and the processes for maintaining their cleanliness.

In recent years, society has become hypervigilant about infection control. In dental care, standards have been established to ensure safety for both patients and practitioners. Specific infection control measures are more visible to patients, such as plastic barriers, personal protective equipment, sterilization indicator tape, and pouches. Less visible are the dental unit waterlines (DUWLs). However, if left unchecked and improperly managed, bacteria in the waterlines could be harmful to both the clinician and the dental patient.

Biofilm background

To adequately discuss best practices for DUWLs, it is important to understand what biofilm is and how it impacts the waterlines in dental offices. Biofilm is a slimy layer of bacteria that thrives in dental waterlines. Biofilm can be hidden in the small waterlines, which have a diameter of approximately 0.5–2 mm.1 The small-diameter tubing makes it difficult to remove the bacteria that collects in the DUWLs due the tubes’ low water flow. DUWLs are used with high-speed dental handpieces, ultrasonic scalers, and air/water syringes.

According to the Centers for Disease Control and Prevention (CDC), DUWL quality for patient treatment should be less than 500 colony-forming units (CFUs) and should be treated according to the manufacturer-specific recommendations to achieve this threshold.1

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A recent health advisory report released in October 2022 by the CDC demonstrated that elevated levels of bacteria and associated infections were reported in DUWLs after pediatric, endodontic, oral surgery, and general dentistry procedures. According to the CDC, “Microorganisms that can be found in untreated DUWLs include Legionella, Pseudomonas aeruginosa, and nontuberculous Mycobacteria.1 Publications, in turn, highlight the need for frequent testing of DUWLs, better understanding among practitioners regarding water quality, and the risks to patients and dental staff associated with elevated bacterial levels. It is important to keep in mind that elderly and immunocompromised patients are at an increased risk of infection transmission due to contaminated DUWLs. An established, robust infection control protocol is vital to patient safety, positive treatment outcomes, and a healthy employer/employee relationship.

Best practices for DUWLs

Dental hygienists take an oath to provide patients with a high standard of care and “to do no harm.” In alignment with this oath, following best practices for frequent testing and proper treatment of DUWLs is the only way to ensure the highest standard of patient care.

How water flows into the dental office impacts the individual practice management protocol for DUWLs. Whether an independent water bottle system is used or municipal water is plumbed directly into the operatories, a chemical germicide should be used to ensure microbiological water quality standards are met. Products such as DentaPure cartridges assist in reducing patient and practitioner bacterial exposure during dental treatment by controlling bacterial growth in the waterlines. These cartridges reduce bacterial exposure for approximately one year using nonallergenic iodinated resin beads.2

There are several relatively simple DUWL infection control measures you can implement into your daily practice:

  • If one-way valves are not being used, it may be necessary for dental hygienists to remind patients not to close their mouth around the saliva ejector. Safe-Flo saliva ejectors with one-way valves reduce potential backflow of saliva and bacteria that can occur should this happen.3
  • Another source of bacterial accumulation in DUWLs that can compromise a water management protocol is unused waterlines, often referred to as dead legs. Any unused waterlines should be properly and effectively terminated.
  • Using warm water during treatment to make patients more comfortable and to decrease root sensitivity can promote colonization of bacteria.4,5 Waterline heaters are not recommended for daily patient treatment.
  • Be sure to flush the DUWLs for 20–30 seconds between patients.

In addition to the day-to-day infection control measures, it is equally important that the bacterial levels of the DUWLs be monitored routinely and treated when high levels of bacteria are indicated.

Regulation of DUWL testing

What is the difference between a recommendation and a requirement? Legally, a recommendation is simply a suggestion or advisement, and a requirement is a demand or a need that must be met.6 Similar to individual state laws, each state’s dental board determines if dental offices are required to regularly test DUWLs, as recommended by the CDC and endorsed by the ADA. In December 2021, Washington became the first state to require expanded routine DUWL testing beyond the CDC’s requirements.7 At the time of this article’s publication, 35 individual state dental boards have adopted the CDC’s recommendations for DUWLs as the standard of care.8

For dental offices to meet these standards of care, both in-office testing and mail-in lab testing services are available. Initially, it may be beneficial to use a mail-in lab testing service that provides exact CFU counts and as a measure to establish a baseline. The in-office tests provide a pass/fail result, allowing dental practices to identify potential biofilm growth issues, which in turn can be implemented as a routine monitoring test.9

It is crucial to note that each waterline in the dental office should be tested. While one DUWL can have a low bacterial load, it does not mean that another DUWL in the same office will have the same test result. According to the Organization for Safety, Asepsis, and Prevention (OSAP), DUWL testing should be performed after the following events: installation of new equipment, initiation of new water protocol, after periods of disuse, and after unit repairs.10

Even if a dental practice uses daily treatment products to minimize the bacterial load in DUWLs, it is still necessary to adhere to routine testing protocol. These adjuncts are not a replacement for routine testing, nor are they a guarantee that the CFUs are at a safe level for patient treatment. They are merely an additional attempt at reducing bacterial buildup in the DUWLs. OSAP recommends continuing to test DUWLs at regular intervals until bacterial levels are acceptable for two consecutive monthly cycles. After this, testing can be reduced to no less than every three months.10

When bacterial levels in DUWLs exceed 500 CFUs, potential next steps for practices may include shocking and/or treating the waterlines, along with additional testing. Liquid Ultra Solution is one example of a product that can be used for shocking DUWLs. It also functions as a cleaner that can be directly added to the independent water bottles themselves.11 This product helps break down existing biofilm and inhibits further production, and is only for independent bottle systems.

VistaTab is an antimicrobial tablet that can be used for routine waterline treatment.12 While these two products can both be used for shocking and maintaining DUWLs, Liquid Ultra Solution is more effective when the CFU count is significantly above the normal range. Any antimicrobial cleaning product must be flushed completely out of the system after use, according to the manufacturer instructions for use (IFU), prior to any successive patient treatment.

IFU for whichever products a dental practice uses to treat DUWLs should be followed as directed. Proper documentation of the test results and protocols should remain on file in the office. This documentation should include the date and location the sample was obtained, the type of test, results, and any remediation needed (including treatment dates and product used).

When discussing best practices for DUWLs, the infection control coordinator (ICC) is an important part of the practice’s execution of infection control protocols. ICC responsibilities could include establishing infection control training schedules, managing or creating reports and logs, maintaining copies of IFU for proper guidance and use of products and equipment, staying current on infection control guidance and protocols, among other duties. It is not the sole responsibility of the ICC to execute the water management plan; success relies on the participation of the entire dental team.

The ICC is often sought when questions or concerns arise about procedures and protocols. Knowledge, expertise, and leadership will be key to thrive in this position. Successful ICCs need to stay abreast of local, state, and national changes in infection control protocols. Resources such as the GreenLight Dental Compliance Center, which offers a comprehensive online guide to infection control protocols specific to each state, can be an asset to the ICC.13

Updating office protocol

Flexibility and implementation are two words that describe the last few years, as dental hygienists have navigated an environment with rapidly changing infection control protocols. Dentistry and infection control are not static; they continually evolve. Dental practitioners should practice the highest standard of care with respect to DUWLs, in addition to their individual state recommendations. The role of the dental hygienist is to care for patients’ overall health, which is why health histories are updated, proper sterilization techniques are practiced, and DUWL protocols should be in place in every dental office. 

Editor's note: This article appeared in the July 2023 print edition of RDH magazine. Dental hygienists in North America are eligible for a complimentary print subscription. Sign up here.


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  2. What you can’t see may harm your patients, your staff, and your practice’s reputation. DentaPure. Crosstex International. 2019. Accessed February 22, 2023. https://www.crosstex.com/sites/default/files/public/dlit00692_rev_b_0419_dentapure_brochure_single_pages_0.pdf
  3. Safe-Flo saliva ejectors. HuFriedyGroup. Accessed April 25, 2023. https://www.hufriedygroup.com/saliva-ejectors/safe-flotm-saliva-ejectors
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  6. The Law Dictionary. Accessed February 23, 2023. https://thelawdictionary.org/recommend
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  8. Dental waterlines: CDC compliance & protecting your practice. Henry Schein. March 8, 2022. Accessed April 27, 2023. https://www.henryschein.com/us-en/dental/events-education/article-Safe-Waterlines.aspx
  9. Waterline testing: what do you need to know? HuFriedyGroup. July 12, 2022. Accessed March 28, 2023. https://www.hufriedygroup.com/blog/dental-water-testing-how-to-ensure-accurate-results
  10. Dental unit water quality: Organization for Safety, Asepsis and Prevention white paper and recommendations—2018. Organization for Safety, Asepsis and Prevention. Updated 2000. Accessed April 27, 2023. https://www.osap.org/assets/docs/resources/toolkits-topics/dental-unit-water-quality-organization-for-safety-asepsis-and-prevention-white-paper-and-recommendations-2018.pdf
  11. Kill biofilm bacteria in dental unit waterlines with Crosstex Liquid Ultra Solution. HuFriedyGroup. Accessed April 1, 2023. https://www.hufriedygroup.com/sites/default/files/2022-10/DMW-TRE-Liquid%20Ultra-Brochure-DLIT00838%20Rev%20B-US-2205.pdf
  12. VistaTab dental waterline cleaner tablets. HuFriedyGroup. Accessed April 5, 2023. https://www.hufriedygroup.com/periodic-treatment/vistatabtm-dental-waterline-cleaner-tablets
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