Dental Unit Waterlines
Studies have shown that colonies of microorganisms,
or biofilms, can form on the inside of the small-bore plastic
tubing that transports water within the dental unit to handpieces
and air-water syringes. Once formed, a biofilm serves as a
reservoir that may dramatically increase the number of free-floating
microorganisms in water used for dental treatment.
Most organisms isolated from dental water
systems originate from the public water supply and do not
pose a high risk of disease for healthy persons. Although
a few pathogenic organisms, such as Legionella spp. and Pseudomonas
sp., have been found, adverse public health threats have not
Dental Unit Water
Despite a lack of documented adverse health
effects, using water of uncertain microbiological quality
is inconsistent with infection control principles. Clearly,
dental unit water quality (DUWQ) is a concern. Levels of contamination
in water from untreated systems can exceed 1 million colony
forming units per milliliter (mL) of water.
Untreated dental units cannot reliably produce
water that meets drinking water standards (fewer than 500
CFU/mL of heterotrophic water bacteria). Even using source
water containing <500 CFU/mL of bacteria (e.g., tap, distilled,
or sterile water) in a self-contained 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.
Dental Water Quality
For routine dental treatment, meet regulatory
standards for drinking water.*
* <500 CFU/mL of heterotrophic water bacteria.
For this reason, CDC recommends that water
used for routine dental treatment meet regulatory standards
for drinking water (fewer than 500 CFU/mL of heterotrophic
Available DUWL Technology
In recent years, commercial devices and
procedures designed to improve the quality of water used in
dental treatment have become widely available. Examples of
methods shown to be effective include the following:
- Self-contained water systems combined with intermittent
or continuous chemical treatment.
- In-line microfilters.
- Combinations of these treatments.
- Another alternative is to bypass the conventional dental
water delivery system entirely and use either autoclavable
or disposable pathways, such as sterile water delivery systems.
As with any dental equipment, always consult with the dental
unit manufacturer for appropriate methods to maintain the
recommended quality of dental water.
Monitoring of dental water quality may be performed using
commercial self-contained test kits or commercial water-testing
laboratories. In-office water-testing systems are available
that work at room temperature using small paddles or plates
of culture medium to reveal bacterial colonies after 72 or
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.
Sterile Irrigating Solutions
During oral surgical procedures, microorganisms may enter
the bloodstream and other normally sterile areas of the oral
cavity (e.g., bone or subcutaneous tissue). For this reason,
sterile solutions (e.g., sterile saline or sterile water)
should be used as a coolant/irrigator when performing surgical
Because the tubing cannot be reliably sterilized, conventional
dental units cannot reliably deliver sterile water even when
equipped with independent water reservoirs. Sterile water
delivery devices, such as sterile irrigating syringes, or
bulb syringes should be used to deliver sterile water. Sterile
water systems, such as those used with surgical handpieces,
bypass the dental unit and use sterile disposable or autoclavable
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