Dental Unit Water Quality
Biofilm is a thin, slimy film of bacteria that sticks to moist surfaces, such as those inside dental unit waterlines. Biofilm occurs in dental unit waterlines because of the long, small-diameter tubing and low flow rates used in dentistry, the frequent periods of stagnation, and the potential for retraction of oral fluids.1 As a result, high numbers of common water bacteria can be found in untreated dental unit water systems. Disease-causing microorganisms found in untreated dental unit water include Legionella, Pseudomonas aeruginosa, and nontuberculous Mycobacteria. Dental health care personnel and patients could be placed at risk of adverse health effects if water is not appropriately treated.
For all non-surgical dental treatment output water, dental health care personnel should use water that meets environmental protection agency regulatory standards for drinking water (i.e., ≤500 colony forming units (CFU)/mL of heterotrophic water bacteria).2 Consult with the dental unit manufacturer for appropriate methods and equipment to maintain the quality of dental water. Commercial devices and procedures designed for this purpose include:
- Self-contained water systems (e.g., independent water reservoir) combined with chemical treatment (e.g., periodic or continuous chemical germicide treatment protocols).
- Systems designed for single-chair or entire-practice waterlines that condition or treat incoming water to remove or inactivate microorganisms.
- Combinations of these methods.
Available products to treat waterlines include tablet systems, continuous release straws and cartridges, initial and periodic shock treatments, and centralized systems. All products and systems must be used and maintained according to the manufacturer instructions for use (IFUs). If you have questions about the IFUs, contact the manufacturer of the treatment product or device that you are using.
For surgical procedures, sterile saline or sterile water should be used as a coolant/irrigant. Conventional dental units cannot reliably deliver sterile water even when equipped with independent water reservoirs containing low-microbial or sterile water because the water-bearing pathway cannot be reliably sterilized. Appropriate delivery devices (e.g., bulb syringe; sterile, single-use disposable products; or sterile water delivery systems that bypass the dental unit by using sterile single-use disposable or sterilizable tubing) should be used to deliver sterile water during surgery.
For all non-surgical pulpal and endodontic procedures, clinicians can also consider using sterile irrigants or antimicrobial solutions.3-6
Monitoring dental unit water quality can help identify problems in performance or adherence with maintenance protocols and provide documentation of compliance. Follow recommendations for monitoring water quality provided by the manufacturer of the unit or waterline treatment product. Commercial self-contained test kits or water-testing laboratories are available for this purpose.
If water testing results exceed the CDC recommended limit of ≤500 CFU/mL of heterotrophic water bacteria, the unit should be treated according to manufacturer IFU, and re-tested immediately after treatment. If a unit remains resistant to treatment over time, it may be necessary to replace waterlines or other water bearing components.
Yes, in October 2022 CDC released a Health Advisory, Outbreaks of Nontuberculous Mycobacteria Infections Highlight Importance of Maintaining and Monitoring Dental Waterlines to provide information about infections associated with contaminated water used during dental procedures. Contaminated water from dental units has been linked to outbreaks of Mycobacteria infections in children.7,8 Case reports also document infections with Mycobacteria and Legionella following endodontic procedures, third molar extractions, and general dental work.9,10 In reported cases, water samples taken from the dental clinics demonstrated levels of bacteria much higher than the recommended levels and reported breakdowns in infection prevention procedures to maintain and monitor dental water quality. These reports highlight the need for training to improve understanding of the underlying principles of dental unit water quality maintenance and monitoring, recommended practices, and their implementation in dental settings.
Ferric sulfate is a medicament used during pulpotomy procedures as a hemostatic agent. Ferric sulfate is recommended conditionally by the American Academy of Pediatric Dentistry as a medicament for pulpotomies.11 Anecdotal reports theorize that because certain types of Mycobacteria are iron-loving, ferric-sulfate may contribute to the severity of Mycobacteria infections associated with pulpotomy procedures. While this is biologically plausible, there is no evidence to demonstrate the use of ferric sulfate during a pulpotomy procedure causes or contributes to a Mycobacteria infection. More evidence is needed to determine what, if any, role ferric sulfate may cause in these infections.
If you wish to report adverse health outcomes regarding a drug or medical device used in your practice, you can contact the US Food and Drug Administration’s (FDA) MedWatch: The FDA Safety Information and Adverse Event Reporting Program.
A boil-water advisory is a public health announcement that the public should boil tap water before drinking it. During a boil-water advisory:
- Do not deliver water from the public water system to the patient through any dental equipment that uses the public water system. This restriction does not apply if the water source is isolated from the municipal water system (e.g., a separate water reservoir or other water treatment device cleared for marketing by the Food and Drug Administration).
- Have patients rinse with bottled or distilled water until the boil-water advisory has been cancelled.
- Do not use tap water to dilute germicides or for hand hygiene unless the water has been brought to a rolling boil for >1 minute and cooled before use.
- For hand hygiene, use antimicrobial products that do not require water (e.g., alcohol-based hand rubs) until the boil-water notice is cancelled. If hands are visibly contaminated, use bottled water and soap for handwashing; if bottled water is not immediately available, use an antiseptic.
When the advisory is cancelled:
- Follow the local water utility’s guidance on flushing all incoming waterlines from the public water system (e.g., faucets, waterlines, and dental equipment). If no guidance is provided, flush dental unit waterlines and faucets for 1 to 5 minutes before using for patient care.
- After the incoming public water system lines are flushed, disinfect dental unit waterlines as recommended by the dental unit manufacturer.
- Guidelines for Infection Control in Dental Health-care Settings – 2003. MMWR2003; 52(No. RR-17):1–66. https://www.cdc.gov/mmwr/PDF/rr/rr5217.pdf. Accessed September 22, 2022.
- US Environmental Protection Agency. National Primary Drinking Water Regulations. https://www.epa.gov/sites/default/files/2016-06/documents/npwdr_complete_table.pdf. Accessed September 22, 2022.
- American Academy of Pediatric Dentistry, Guidelines for Infection Control, https://www.aapd.org/research/oral-health-policies–recommendations/infection-control/. Accessed September 22, 2022.
- American Academy of Pediatric Dentistry, Pulp Therapy for Primary and Immature Permanent Teeth, https://www.aapd.org/media/Policies_Guidelines/BP_PulpTherapy.pdf. Accessed September 22, 2022.
- American Association of Endodontists, AAE Position Statement on Vital Pulp Therapy,. Accessed September 22, 2022.
- Organization for Safety, Asepsis and Prevention (OSAP). Dental Unit Water Quality: Organization for Safety, Asepsis and Prevention White Paper and Recommendations– 2018. 1, Issue 1, 2018 October 31.
- Hatzenbuehler LA, Tobin-D’Angelo M, Drenzek C, Peralta G, Cranmer LC, Anderson EJ, Milla SS, Abramowicz S, Yi J, Hilinski J, Rajan R, Whitley MK, Gower V, Berkowitz F, Shapiro CA, Williams JK, Harmon P, Shane AL. Pediatric Dental Clinic-Associated Outbreak of Mycobacterium abscessus Infection. J Pediatric Infect Dis Soc. 2017 Sep 1;6(3):e116-e122. doi: 10.1093/jpids/pix065. PMID: 28903524.
- Singh J, O’Donnell K, Nieves DJ, Adler-Shohet FC, Arrieta AC, Ashouri N, Ahuja G, Cheung M, Holmes WN, Huoh K, Tran L, Tran MT, Pham N, Zahn M. Invasive Mycobacterium abscessusOutbreak at a Pediatric Dental Clinic. Open Forum Infect Dis. 2021 Apr 15;8(6):ofab165. doi: 10.1093/ofid/ofab165. PMID: 34113683; PMCID: PMC8186244.
- Pérez-Alfonzo R, Poleo Brito LE, Vergara MS, Ruiz Damasco A, Meneses Rodríguez PL, Kannee Quintero CE, Carrera Martinez C, Rivera-Oliver IA, Da Mata Jardin OJ, Rodríguez-Castillo BA, de Waard JH. Odontogenic cutaneous sinus tracts due to infection with nontuberculous mycobacteria: a report of three cases. BMC Infect Dis. 2020 Apr 21;20(1):295. doi: 10.1186/s12879-020-05015-5. PMID: 32316920; PMCID: PMC7171849.
- Ricci ML, Fontana S, Pinci F, et al. Pneumonia associated with a dental unit waterline. Lancet2012; 379(9816):684.
- American Academy of Pediatric Dentistry, Use of Vital Pulp Therapies in Primary Teeth with Deep Caries Lesions, https://www.aapd.org/media/Policies_Guidelines/G_VPT.pdf. Accessed September 22, 2022.