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Oral Health Topics

Dental Unit Waterlines

Background: Organized dentistry has traditionally assumed responsibility for assessing and improving the quality of dental care provided to patients. The widespread adoption of enhanced infection control methodologies by dental practitioners is just one example of the profession’s commitment to high quality patient care.

In 1995, the American Dental Association Board of Trustees and ADA Council on Scientific Affairs adopted a statement on dental unit waterlines. This statement was in response to scientific evidence that the microbiologic quality of water used in dental treatment could be improved; and called for the design of dental equipment so that, by the year 2000, water delivered to patients during nonsurgical dental procedures consistently contained no more than 200 colony-forming units per milliliter (cfu/ml) of aerobic mesophilic heterotrophic bacteria at any point in time in the unfiltered output of the dental unit. Since 1995, technological advances have made this goal possible. In addition, the CDC now recommends that coolant water used in non-surgical dental procedures meet EPA regulatory standards for drinking water, which is less than or equal to 500 colony forming units of heterotrophic bacteria per milliliter of water. This CDC recommendation was published in their Guidelines for Infection Control in Dental Health-Care Settings—2003 (CDC has different guidelines about water used in oral surgical procedures). Considering these developments, a statement was adopted in 2004 to update the 1995 ADA statement on dental unit waterlines.

In 2012, a case report was published concerning an 82-year-old otherwise healthy woman who developed Legionnaire’s disease after a dental visit.1 The current statement updates the 2004 ADA statement on dental unit waterlines to recognize this case report.

The Council is sensitive to heavy regulatory burden imposed on dentists in recent years by various federal, state and local government agencies. In some cases, the regulations have been based on limited science. The Council reaffirms its strong belief that both the profession and the public are served when recommendations affecting dental practice are based on sound science and take into account their cost in light of their expected benefit. The recommendations that follow are made in light of these considerations.

Dental unit waterlines must be maintained regularly to deliver water of an optimal microbiologic quality. Although infection associated with microbial contamination of waterlines appears to be rare, it has been shown that the level of microorganisms in untreated dental unit waterlines is greater than 500 CFU/mL, which exceeds the drinking water standard. Colonization of microorganisms within the waterlines-while it may not be a concern to healthy individuals-might place elderly or immunocompromised patients at unnecessary risk. Dental unit waterlines (the tubes that connect the high-speed handpiece, air/water syringe and ultrasonic scaler to the water supply) have been shown to harbor, in significant numbers, a wide variety of microorganisms including bacteria, fungi, and protozoans. These microorganisms colonize and replicate on the interior surfaces of the waterline tubing, inevitably resulting in adherent heterogeneous microbial accumulations termed “biofilms”. Biofilms, once formed, serve as a reservoir significantly amplifying the numbers of free-floating microorganisms in the water exiting the waterlines. It has been suggested that heating dental unit water to increase patient comfort, as is the practice in some dental offices, may further augment biofilm formation. In dental unit waterline systems that are not maintained, these microbial accumulations can contribute to occasional objectionable odors and visible particles of biofilm material exiting the system.

Water Quality Improvement: Dental unit water systems designed for general dental practice must be regularly maintained in order to deliver water of an optimal microbiologic quality. Manufacturers of dental equipment are encouraged to continue to develop accessory components that can be retrofitted to dental units currently in use, whatever the water source (public or independent), to aid in achieving this goal. Further, the ADA urges industry to continue to ensure that all dental units manufactured and marketed in the U.S.A. in the future have the capability to be equipped with a separate water reservoir independent of the public water supply. In this way, dentists not only will have better control over the quality of the source water used in patient care, but also will be able to avoid interruptions in dental care when “boil water” notices are issued by local health authorities.

In 1993, CDC recommended that dental waterlines be flushed at the beginning of the clinic day to reduce the microbial load. However, studies have demonstrated this practice does not affect biofilm in the waterlines or reliably improve the quality of water used during dental treatment. Dental unit water that remains untreated or unfiltered is unlikely to meet drinking water standards, <500 CFU/mL, therefore, one or more commercial devices and procedures designed to improve the quality of water should be employed. At the present time, commercially available options for improving dental unit water quality include the use of:

  • Independent water reservoirs
  • Chemical treatment regimens
  • Source water treatment systems
  • Daily draining and air purging regimens
  • Point-of-use filters

Additionally, strict adherence to maintenance protocols is required to sustain the quality of dental unit water. Industry and independent researchers are strongly encouraged to continue to explore the possible alternatives and adjuncts to the above listed options. Dental practitioners should always consult with the manufacturer of their dental units before initiating any waterline treatment protocol.

Water Quality Monitoring: It is important that waterline treatment schedules include water quality monitoring. Simple and inexpensive methods to estimate the number of free-floating heterotrophic bacteria in dental unit water are available. A well-designed water quality indicator should be self-contained and easy to use in-office; accurately detect a wide concentration range and type of aerobic mesophilic heterotrophic waterborne bacteria within a reasonable incubation time at room temperature; and be relatively inexpensive to use. In addition to in-office testing kits, laboratories across the U.S. also offer mail-in testing services.

Delivery of Sterile Surgical Irrigation: According to the 2003 CDC Recommendations, “Sterile solutions such as sterile saline or sterile water should be used as a coolant/irrigation in the performance of oral surgical procedures. Oral surgical procedures involve the incision, excision, or reflection of tissue that exposes the normally sterile areas of the oral cavity including biopsy, periodontal surgery, apical surgery, implant surgery, and surgical extractions of teeth (removal of erupted or nonerupted tooth requiring elevation of mucoperiosteal flap). Conventional dental units cannot reliably deliver sterile water even when equipped with independent water reservoirs because the water-bearing pathway cannot be reliably sterilized. Delivery devices (e.g., bulb syringe or sterile, single-use disposable products) should be used to deliver sterile water. Oral surgery and implant handpieces, as well as ultrasonic scalers, are commercially available that bypass the dental unit to deliver sterile water or other solutions by using single-use disposable or sterilizable tubing.”

Training and Education: The ADA has resources available to educate dental practitioners regarding microbial contamination and biofilm formation in dental unit waterlines, and improving the quality of water delivered to patients. Additionally, manufacturers should be active in training and educating the profession in the proper use and maintenance of their systems.

In summary, the Council recognizes that the scientific literature supports the need for improvement in dental unit water quality. The Council will continue to work with industry and the research community to address research and development needs that will allow the delivery of water of an optimal microbiological quality to the dental patient. The Council recommends dissemination of this information to dentists as part of the ADA’s ongoing service to the profession and the public.

1. Ricci ML, Fontana S, Pinci F, et al. Pneumonia associated with a dental unit waterline. Lancet 2012;379(9816):684. April 2012

Cleaning Dental Unit Waterlines

1. Identify the source of water for your dental unit.

Municipal water supply This source may provide limited access to the waterline, but in such instances there are options for controlling water quality: 1) install a point-of-use filter between the dental instrument and the waterline tubing, 2) retrofit the dental unit so that the water is supplied by a self-contained water system for easy delivery of chemical treatments (contact the dental unit manufacturer about installing a self-contained water system), or 3) install a system that allows delivery of cleaning agents at the junction box.

Self-contained water system A reservoir (bottle) that attaches to the dental unit waterline, which isolates it from the municipal water supply. Water (tap, distilled, sterile etc.) must be added manually. The simple task of regularly adding cleaning agents to the bottle make this a convenient system.

2. Identify products that fit your needs and are compatible with your dental unit (contact the dental unit manufacturer). Some cleaning agents, like bleach, can corrode parts of the dental unit.

3. Develop a schedule for waterline maintenance (based on manufacturer recommended treatment methods) and assign the duty to a particular person.

4. Establish a protocol for monitoring the quality of dental unit water.


Inclusion or omission of any product in the following tables does not imply its endorsement, approval, or disapproval by the ADA (report omissions to science@ada.org). This information was collected from publicly accessible documents.

Filters may be installed in-line near the point-of-use (e.g. between the waterline and the dental instrument) to block the passage of microorganisms. Filters will have no effect on the development of biofilm in the waterlines, but will remove microorganisms as the water is delivered to the patient. Filters must be periodically replaced, the frequency of which will depend on the amount of biofilm in the waterlines. Filters may or may not remove endotoxin.


Mode of action

Contact information


In-line filter

0.22 micron pore size

Pall Corporation
Ann Arbor, MI


In-line filter that continuously releases iodine

0.22 micron pore size

Fergus Falls, MN

Chemicals remove, inactivate, or prevent formation of biofilm. Chemical treatments are either continuously infused into, or are intermittently added to, the dental unit water. These products may not result in delivery of purified water should the water pass through waterlines containing biofilm. If the waterline is contaminated with biofilm, it may be necessary to remove the biofilm with another treatment before using the products described below. Consult the directions for use.


Tablet added to water bottle for continuous use

ProEdge Dental Products
Centennial, CO


Tablet added to water bottle

Newberg, OR

IGN 500

Proprietary chemical for continuous use

Airel West

Micrylium Lines

Chlorhexidine gluconate based for intermittent use

Micrylium Laboratories
Toronto, ON, Canada


Water, glycerin, alcohol, chlorhexidine gluconate,

xylitol, dye for continuous

or intermittent use

Anodia Systems
Danville, KY

Sterisil CartridgeTM

In-line cartridges continuously clean and maintain dental unit waterlines

Sterisil, Inc.
Palmer Lake, CO


Tablets added to bottle for continuous use. Clean and maintain waterlines.

Sterisil, Inc.
Palmer Lake, CO

Citrisil Shock

Tablets for intermittent use

Sterisil, Inc.
Palmer Lake, CO

Sterilex Ultra

Hydrogen peroxide based for intermittent use


VistaCleanTM Aqueous cleaner derived from natural citrus botanicals for continuous or intermittent use Vista Research Group
 Ashland, OH 419.281.3927

Water Quality Monitoring 

The only way to know that a dental unit waterline cleaning regimen is effective is to test the water coming out of the unit. Dental unit water testing products and services are used to monitor the dental unit water quality. Testing is usually done using three samples of water taken from the same dental unit. Dental equipment (e.g. handpieces) should be removed before the samples are taken. It is important that you do not contaminate the water during sampling; therefore, wear gloves and follow the directions for the particular product or service carefully.

The following is a list of dental unit water testing products and services available to the dental profession. Currently, the American Dental Association does not have an evaluation program for these products or services. The listing or omission of a product or service does not imply endorsement, approval, or disapproval by the Association (report omissions to science@ada.org). Not all biological monitors can

be used with all types of sterilization devices; contact the manufacturer regarding the proper use of these products.

Dental Unit Water Quality Testing Products (for in-office use)

HPC Total Count Sampler (product # MHPC10025)
Billerica, MA
Phone: (800) 645-5476

Disinfection Control Paddle Tester (product # 26195-10)
Hach Company
Loveland CO
Phone: (800) 227-4224

Dental Unit Water Quality Testing Services 

E-mail: info@aquaknow.com
Phone: (877) 734-7661

Loma Linda University School of Dentistry
E-mail: SAS@llu.edu
Phone: (909) 558-8069 or (909) 558-8176 

MicroTest Laboratories
E-mail: microtestlabsinc@yahoo.com
Phone: (800) 713-3334 

ProEdge Dental Products
E-mail: miker@proedgedental.com
Phone: (888) 843-3343

The Texas A&M University System Health Science Center
Baylor College of Dentistry
E-mail: cdms@bcd.tamhsc.edu
Phone: (214) 370-7214


Biofilm – Slime producing bacterial communities that may also harbor fungi, algae, and protozoa. These microorganisms colonize and replicate on the interior surfaces of waterline tubing, creating adherent microbial accumulations.

Colony-forming unit – The minimum number of separable cells that can give rise to a visible colony.

Endotoxin – Part of the outer layer of the cell wall of Gram-negative bacteria that is associated with the lipopolysaccharide complex. Pathogenic and non-pathogenic bacteria can release endotoxins. Endotoxins are heat stable but can be degraded by oxidizing agents (e.g. peroxide and hypochlorite).

Heterotrophic bacteria – Bacteria that require a carbon source to grow. These bacteria are not necessarily harmful, but determining the heterotrophic plate count is used as an indication of the amount of residual disinfectant present in a water supply.

Point-of-entry filters – Filter water entering the dental unit.

Point-of-use filters – Filter water exiting the dental unit. Usually installed between the waterline and the dental instrument.

Additional Resources