Pillar GuideInvisible ≠ clean
Biofilm in Dental Waterlines
How biofilm forms in dental unit waterlines, why it resists flushing, and what a maintenance protocol has to do about it.
ReadGuidesCase Studies
Documented Dental Waterline Infection Outbreaks
Two documented pediatric dental clusters involved pulpotomies, untreated municipal water, and no waterline monitoring program.
The short version
Key takeaways
- In a Georgia pediatric dentistry practice in 2015, CDC and the Georgia Department of Public Health investigated Mycobacterium abscessus infections among 24 children who had undergone pulpotomies, 14 of whom were confirmed cases, with a median age of 7.3 years.
- Georgia investigators found the practice was using municipal water without a waterline disinfectant and was not monitoring water quality; M. abscessus isolates from the dental unit water matched isolates from patient tissue.
- At an Orange County, California pediatric clinic in 2016, 71 case patients (22 confirmed, 49 probable) were identified among 1,082 at-risk patients following pulpotomy procedures, with a median age of 6 years and median symptom onset 85 days after the procedure.
- Pulpotomy is not classified as a surgical procedure, so it does not trigger CDC's sterile solution recommendation. Waterline water quality, rather than sterile technique, was therefore the controlling factor in both clusters.
- CDC issued a Health Advisory on October 31, 2022 reinforcing existing recommendations for maintaining and monitoring dental unit waterlines.
Georgia, 2015
What happened in the Georgia dental waterline outbreak?
CDC and the Georgia Department of Public Health investigated Mycobacterium abscessus infections among 24 children treated at a pediatric dentistry practice, 14 of whom met the confirmed case definition. All had undergone pulpotomies. The practice was using municipal water with no waterline disinfectant and was not monitoring water quality; M. abscessus recovered from the dental unit water matched isolates from patient tissue.
The genetic match made this case decisive rather than circumstantial. Investigators recovered M. abscessus from water sampled at the dental units and found the isolates identical to eight isolates taken from the tissue of seven patients. They concluded that the dental unit water was the source.
| Setting | A pediatric dentistry practice |
|---|---|
| Procedure | Pulpotomy |
| Children affected | 24 investigated; 14 (58%) confirmed cases |
| Median age | 7.3 years |
| Median onset | 74 days after the pulpotomy |
| Clinical findings | Cervical lymphadenitis in 100% of cases; mandibular or maxillary osteomyelitis in 48%; pulmonary nodules in 37% |
| Waterline practice | Municipal water in use, no waterline disinfectant, no routine water quality monitoring |
The Delay Is the Difficulty
A median of 74 days between the procedure and symptom onset means an affected child presents long after the appointment, usually to a different clinician, with a swollen jaw and no obvious connection to dentistry. Clusters of this kind are found by public health surveillance, not by the practice.
Orange County, California, 2016
What happened in the Orange County dental clinic outbreak?
Odontogenic Mycobacterium abscessus infections occurred among patients who had pulpotomies at a pediatric dental clinic between January 1 and September 6, 2016. Of 1,082 at-risk patients, investigators identified 71 case patients: 22 confirmed and 49 probable. The median age was 6 years, and the median symptom onset was 85 days after the procedure.
| Setting | A pediatric dental clinic |
|---|---|
| Procedure | Pulpotomy |
| At-risk patients | 1,082 |
| Case patients | 71 total: 22 confirmed, 49 probable |
| Median age | 6 years |
| Median onset | 85 days after the pulpotomy |
| Imaging findings | Abnormalities of the mandible or maxilla in 49 of 70; lymphadenopathy in 13 of 70; pulmonary nodules in 19 of 68 |
At one clinic over eight months, more than 1,000 children were exposed and 71 became cases. Treatment for invasive M. abscessus is prolonged, and the reported outcomes included jaw surgery.
What the Two Clusters Share
| Georgia, 2015 | Orange County, 2016 | |
|---|---|---|
| Organism | Mycobacterium abscessus | Mycobacterium abscessus |
| Procedure | Pulpotomy | Pulpotomy |
| Patients | Children, median 7.3 years | Children, median 6 years |
| Delay to symptoms | Median 74 days | Median 85 days |
| Source | Dental unit water; isolates genetically matched to patient tissue | Contaminated dental unit waterlines identified as the suspected source |
Why pulpotomies, in both cases
A pulpotomy exposes dental pulp but is not classified as a surgical procedure, so it does not trigger the recommendation to use sterile irrigating solutions. Practices therefore commonly irrigate with water from the dental unit, making the microbial quality of that water the controlling variable rather than sterile technique.
Waterlines still need treatment regardless of procedure classification. The line between “surgical” and “nonsurgical” does not track the line between exposed and unexposed tissue. California later addressed this directly by making irrigation of exposed pulp with water that is neither sterile nor disinfecting a form of unprofessional conduct.
What Changed Afterwards
What did CDC do in response to the dental waterline outbreaks?
CDC issued a Health Advisory through the Health Alert Network on October 31, 2022, reinforcing existing recommendations for maintaining and monitoring dental unit waterlines. The advisory did not introduce a new standard. It restated guidance already in place because the clusters showed that practices were not following it consistently.
Guidance covering both practices had existed since 2003, but neither practice was treating or monitoring its waterlines. The problem was inconsistent implementation and a lack of records.
Implications for a Practice Today
A practice needs a treatment protocol that staff perform consistently and test records that demonstrate it. Neither practice above had those records, so neither knew the protocol was failing.
Frequently Asked Questions
Have dental waterlines caused documented infections?
Yes. Two documented pediatric clusters, at a Georgia practice in 2015 and an Orange County, California clinic in 2016, were traced to dental unit water. In the Georgia investigation, organisms recovered from the waterlines genetically matched those found in patient tissue.
What organism was involved in the dental waterline outbreaks?
Mycobacterium abscessus, a rapidly growing nontuberculous mycobacterium. CDC also names Legionella and Pseudomonas aeruginosa among organisms found in untreated dental unit water.
Why were pulpotomies involved in both outbreaks?
A pulpotomy exposes dental pulp but is not classified as a surgical procedure, so it does not trigger the recommendation to use sterile solutions. Practices therefore commonly use dental unit water for irrigation, which makes the water quality in the line the controlling variable.
What did CDC change after these outbreaks?
CDC issued a Health Advisory on October 31, 2022 through the Health Alert Network, reinforcing existing recommendations for maintaining and monitoring dental unit waterlines rather than introducing new ones. The advisory's message was that the guidance already in place was not being followed consistently.
Sources
- Mycobacterium abscessus Infections Among Patients of a Pediatric Dentistry Practice, Georgia, 2015CDC Morbidity and Mortality Weekly Report 65(13) · Published April 8, 2016 · Last checked August 13, 2026
- Invasive Mycobacterium abscessus Outbreak at a Pediatric Dental ClinicOpen Forum Infectious Diseases 8(6) · Published April 6, 2021 · Last checked August 13, 2026
- Health Advisory: Preventing Infections Associated with Dental Unit WaterlinesCenters for Disease Control and Prevention · Published October 31, 2022 · Last checked August 9, 2026
- Best Practices for Dental Unit Water QualityCenters for Disease Control and Prevention · Published May 15, 2024 · Last checked August 9, 2026
Requirements vary by state and by equipment manufacturer. Always follow your dental unit and treatment product instructions for use, and confirm current rules with your state dental board.
Next step
The protocol these cases were missing
Shock the lines, treat them continuously, test on a schedule, and keep the record. LineTab provides continuous treatment with one tablet per reservoir refill.