A children’s dental clinic in Anaheim, CA has been identified as responsible for transmitting Mycobacterium abscessus, a rare bacterial infection. M. abscessus is found in dust, water, and soil and known to contaminate medical devices. Mycobacterium can contaminate a water supply when found in large numbers or when it is a particularly virulent strain.

As of September 27th, three confirmed and nineteen probable infections have been traced to the clinic. Upon investigation, the Orange County Health Care Agency found high levels of microorganisms in the office water supply, and ultimately, they traced the infection to the clinic’s dental unit waterlines. The practice is no longer using office water for patient procedures.

All of the affected children had pulpotomies. According to Dr. Eric Handler, health officer with the Orange County Health Authority, "The reason we're so concerned is this infection is very hard to treat with antibiotics." Often, infected tissue must be surgically removed. "Treatment can be very traumatic and deforming," explained Dr. Handler.

Biofilm

According to the CDC, studies have demonstrated that dental unit waterlines can become colonized with microorganisms, including bacteria, fungi, and protozoa, which promotes the development of biofilm. While these microbes may not affect healthy individuals, they can be harmful to certain populations (e.g., young children, elderly individuals, and immunocompromised patients).

Standards for Optimal Dental Unit Water Quality

All dental offices should be following accepted infection control principles. Dental infection prevention guidance, including management of dental unit water quality, can be found in the CDC Guidelines for Infection Control in Dental Health-Care Settings, 2003. This publication offers recommendations for preventing and controlling infectious diseases and managing health and safety concerns related to infection control in dental settings. The information below is taken from the Guidelines and reflects the CDC’s recommendations for maintaining dental unit water quality.

In accordance with the ADA, OSAP, and CDC, the number of bacteria in water used as a coolant / irrigant for nonsurgical dental procedures should, at a minimum, be as low as reasonably achievable, or <500 CFU/mL, the regulatory standard for safe drinking water established by the Environmental Protection Agency (EPA), the American Public Health Association (APHA), and the American Water Works Association (AWWA). Because conventional dental units cannot reliably deliver sterile water even when equipped with independent water reservoirs, delivery devices (e.g., bulb syringe or sterile, single-use disposable products) should be used to deliver sterile water for oral surgical procedures.

Improving Dental Unit Water Quality

Unfortunately, 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.

In addition, patient material (e.g., oral microorganisms, blood, and saliva) can enter the dental water system during patient treatment. Dental devices that are connected to the dental water system and that enter the patient’s mouth (e.g., handpieces, ultrasonic scalers, or air / water syringes) should be operated to discharge water and air for a minimum of 20–30 seconds after each patient. This procedure is intended to physically flush out patient material that might have entered the turbine, air, or waterlines. The majority of recently manufactured dental units are engineered to prevent retraction of oral fluids, but some older dental units are equipped with anti-retraction valves that require periodic maintenance. Users should consult the owner’s manual or contact the manufacturer to determine whether testing or maintenance of anti-retraction valves or other devices is required. Even with anti-retraction valves, flushing devices for a minimum of 20– 30 seconds after each patient is recommended.

Maintaining and Monitoring Dental Unit Water

Dental workers should be trained regarding water quality, biofilm formation, water treatment methods, and appropriate maintenance protocols for water delivery systems. Water treatment and monitoring products require strict adherence to maintenance protocols, and noncompliance with treatment regimens has been associated with persistence of microbial contamination in treated systems. Clinical monitoring of water quality can ensure that procedures are correctly performed and that devices are working in accordance with the manufacturer’s standards.

Dentists should consult with the manufacturer of their dental unit or water delivery system to determine the best method for maintaining acceptable water quality (i.e., <500 CFU/mL) and the recommended frequency of monitoring. Monitoring of dental water quality can be performed by using commercial self-contained test kits or commercial water-testing laboratories.

References

Ross, Erin. Infection Outbreak Shines Light On Water Risks At Dentists Offices. Web Blog Post. SHOTS: Health News from NPR, 30 Sept. 2016. http://www.npr.org/sections/health-shots/2016/09/30/495802487/infection-outbreak-shines-light-on-water-risks-at-dentists-offices

Centers for Disease Control and Prevention. (December 19, 2003). Guidelines for Infection Control in Dental Health-Care Settings (MMWR Publication No. 52 [RR17]; 1-61). http://www.cdc.gov/Mmwr/preview/mmwrhtml/rr5217a1.htm