CDC's dental waterline advisory: 500 CFU/mL for routine water, sterile for surgery, after NTM outbreaks in children

What it says#

CDC distributed Health Advisory CDCHAN-00478 through its Health Alert Network on October 31, 2022, "to emphasize the importance of following existing recommendations for maintaining and monitoring dental waterlines." The occasion was that "multiple outbreaks of nontuberculous Mycobacteria (NTM) infections have occurred in children who received pulpotomies in pediatric dental clinics where the dental treatment water contained high levels of bacteria." In March 2022, CDC had been notified of a new cluster of suspected NTM infections in children after dental procedures at a pediatric clinic; the investigation was ongoing at the time, and "preliminary site visit data report that dental unit waterline testing results showed microbial counts much higher than the level recommended by CDC."

The advisory describes the two earlier outbreaks in detail. In 2015, 24 cases of odontogenic NTM infection were reported in children who had pulpotomies at a pediatric dental clinic in Georgia. The clinic used municipal water during procedures, was not using a disinfectant in its waterlines and was not monitoring water quality; testing "showed very high microbial counts of Mycobacterium abscessus," and the isolates from the water "were found to be identical to eight isolates from tissue samples from seven of the patients." In 2016, a clinic in Orange County, California had 71 patients identified with odontogenic NTM infections after pulpotomies. Municipal water stored in a pressurized bladder tank was used to fill the unit bottles; there was no disinfectant and no monitoring; every water sample exceeded the CDC level, and multiple NTM species were found in syringe water from five of six treatment rooms. The children were 4 to 8 years old. Many "developed severe infections with clinical diagnoses such as cervical lymphadenitis and mandibular or maxillary osteomyelitis," needed hospitalization, intravenous antibiotics and surgery, and were left with "permanent tooth loss, hearing loss, facial nerve palsy, and incision fibrosis."

The rule the advisory restates has three tiers. First, "because of the potential to form biofilm, CDC recommends that all dental unit waterlines be treated regularly with disinfectants to meet the Environmental Protection Agency (EPA) regulatory standards for drinking water (i.e., ≤500 colony forming units (CFU)/mL of heterotrophic water bacteria)," and that water is what "all non-surgical dental procedures" use. EPA's drinking-water table lists the heterotrophic plate count treatment technique as "no more than 500 bacterial colonies per milliliter." Second, "for all oral surgical procedures, use sterile saline or sterile water as a coolant or irrigant," delivered by a bulb syringe, a sterile single-use disposable product, or "sterile water delivery systems that bypass the dental unit by using sterile single-use disposable or sterilizable tubing." The advisory defines oral surgical procedures as those involving "the incision, excision, or reflection of tissue that exposes the normally sterile areas of the oral cavity," with examples: biopsy, periodontal surgery, apical surgery, implant surgery, and surgical extractions including removal of an erupted or nonerupted tooth requiring a mucoperiosteal flap, bone removal or tooth sectioning. Third, "for all non-surgical pulpal therapy and endodontic procedures, consider following more conservative recommendations" from the American Academy of Pediatric Dentistry, the American Association of Endodontists and the Organization for Safety, Asepsis and Prevention, "which recommend irrigation with a sterile and/or antimicrobial solution."

Around those tiers sit the routines. Consult the unit manufacturer on methods and equipment to maintain water quality; "follow recommendations for monitoring water quality provided by the manufacturer of the unit or waterline treatment product"; and "discharge water and air for a minimum of 20-30 seconds after each patient from any device connected to the dental water system that enters the patient's mouth." For facilities: an infection prevention plan "that includes policies and standard operating procedures dedicated to maintaining and monitoring water quality"; training "based on the manufacturer's instructions for use," given to all new hires, when new equipment is purchased "and then at least annually"; and documentation of "all maintenance records, monitoring results, and employee trainings," kept "according to state and federal requirements." Suspected health-care-associated infections, including from dental care, are to be reported to public health authorities. CDC's current Dental Unit Water Quality page, dated May 15, 2024, adds one sentence the advisory does not: "All dental units should use systems that treat water to meet drinking water standards (i.e., ≤500 CFU/mL of heterotrophic water bacteria). Independent reservoirs, or water-bottle systems, alone are not sufficient." The 2003 guideline explains why: "simply using source water containing <500 CFU/mL of bacteria (e.g., tap, distilled, or sterile water) in a self-contained water system will not eliminate bacterial contamination in treatment water if biofilms in the water system are not controlled. Removal or inactivation of dental waterline biofilms requires use of chemical germicides."

Who it applies to#

The advisory's recommendations are addressed to "dental providers" and "dental facilities" without carving out any setting. Every operatory with a handpiece, an air/water syringe or an ultrasonic scaler has the tubing CDC describes. The outbreaks were pediatric and the procedure was the pulpotomy, but the 500 CFU/mL standard applies to routine water for every non-surgical procedure on every patient, and the sterile-irrigant rule applies to every flap extraction, implant and periodontal or apical surgery in a general office.

What the advisory does not say is how often to test. It defers to the manufacturer of the unit or the treatment product, as the 2003 guideline does. CDC's own Dental Unit Waterlines Workgroup told HICPAC on August 22, 2024 that the current guidelines have "no recommended frequency for monitoring water quality," "no recommendation for follow-up steps if monitoring results exceed recommended limit," and "no recommendation for use of water during pulpal therapy procedures," and that the workgroup, meeting since July 2023, was drafting an update. That material is labeled draft and "should not be construed to represent any agency determination or policy." As of the check date, the 2003 guideline, the 2016 summary and the 2022 advisory remain the operative CDC documents.

What changed#

Nothing in the standard changed in 2022; the advisory says so in its first sentence. What changed is that CDC put a dental-equipment failure in a Health Alert Network message and attached named outbreaks with counts, ages and outcomes to a number that had lived quietly in a 2003 guideline. The two earlier outbreaks share one description: municipal water in the bottle, no disinfectant, no monitoring. That describes a great many operatories, which is why the advisory reads as a warning to the whole profession rather than to two clinics.

The 2024 page update closed the loophole most offices relied on, the belief that a bottle system with clean source water was itself the control. The HICPAC workgroup's stated gaps, frequency, follow-up and pulpal therapy, are the questions an owner still has to answer with the manufacturer's instructions and the specialty organizations' guidance.

Where the source is#

The advisory lives on CDC's archive subdomain, archive.cdc.gov, where CDC moved older HAN messages; it is free and loaded without difficulty. CDC's Dental Unit Water Quality page and the Summary of Infection Prevention Practices are on cdc.gov and loaded with full browser headers, though cdc.gov refused automated downloads of its PDFs, so the 2003 guideline is linked here in its MMWR web version and the 2016 summary as its web page. The HICPAC workgroup slides of August 22, 2024 were read from the PDF at cdc.gov/hicpac and are cited only for the gaps they list. EPA's drinking-water regulations page, the source of the 500 per milliliter figure, is on epa.gov. The AAPD, AAE and OSAP documents the advisory points to were not read for this entry.