Dental Unit Waterlines Chapter 24 Flashcards
Introduction
Outbreaks of waterborne disease have
occurred in a broad range of facilities
Published reports have associated
illness with exposure to water from
dental units
Bacteria capable of causing disease in
human beings are found in DUWLs,
which is reason for concern
In community water, the number of
waterborne bacteria is kept to fewer than
500 colony-forming units (CFUs) per
milliliter
The water from air-water syringes and
dental handpieces often has bacterial
levels hundreds or thousands of times
greater than those permissible in drinking
water
The types of bacteria that are found in
dental unit water are frequently the same
types found in community wate
Background
Dental healthcare workers are exposed to
Legionella bacteria at a much higher rate
than are members of the general public
Dental personnel are exposed to
contaminated DUWLs through inhalation of
the aerosol generated by the handpiece and
air-water syringe
At least one suspected fatality of a dentist
resulting from legionellosis has been recorded
Published case reports have described
immunocompromised patients in whom
postoperative infections developed as a result
of contaminated dental water
Microorganisms in Dental Unit
Water
Primary source of microorganisms in
DUWLs is the public water supply
Saliva can be retracted into DUWLs during
treatment (“suckback”)
Antiretraction valves on dental units and
thorough flushing of the dental lines
between patients minimize the chance of
suckback
The public water source has a CFU count
of less than 500/ml before entering the
DUWLs; once that water enters the DUWLs
and colonizes within the biofilm, the CFU count shyrockets
Sources of Microorganisms
There are two communities of bacteria
in DUWLs
One bacterial community exists in the water
itself: planktonic (free-floating)
The other exists in the biofilm attached to
the walls of the DUWLs
Biofilm
Biofilm exists in all places in which
moisture and a suitable solid surface are
found
Biofilm consists of bacterial cells and other
microbes that adhere to surfaces and form
a protective slime layer
Biofilm can contain many types of bacteria,
as well as fungi, algae, and protozoa
Viruses, such as the human
immunodeficiency virus, cannot multiply in
DUWLs
Biofilm in Dental Waterlines
At the dental unit, the water enters plastic
waterlines, which pass through a
multichannel control box that allows the
water to be distributed to the hoses that
feed various attachments, such as high-
speed handpieces, air-water syringes, and
ultrasonic scalers
DUWLs have a narrow tube (⅛ to 1⁄16 inch)
Biofilm forms on the inside of DUWLs as
water flows through the unit
Bacterial Characteristics
Bacteria embedded in the protective
biofilm (slime layer) are extremely
difficult to remove or kill
Bacteria in the biofilm are up to 1500
times more resistant to chemical
germicides than are planktonic (free-
floating) bacteria
During use of the dental handpiece or
air-water syringe, some bacteria already
present in the incoming public water, as
well as bacteria dropping off the biofilm,
are carried out
Growth-Promoting Factors
Several factors contribute to the
formation of biofilm in DUWLs
Water moves at normal line pressure
(slowly)
Intermittent stagnation of water inside the
units typically occurs between patients,
overnight, and over weekends, allowing
planktonic communities of bacteria to
attach to the walls of the tube
The bacteria become stabilized on a
surface, and the nutrients in the water feed
them
Microfiltration Cartridges
Disposable inline microfiltration cartridge
can dramatically reduce bacterial
contamination in dental unit water
Device must be inserted as close to the
handpiece or air-water syringe as possible
Use of filtration cartridges combined with
water reservoirs ensures improved water
quality
Cartridges must be changed according to
the manufacturer’s recommendations
Self-Contained Water Reservoirs
Supply air pressure to the water bottle
(reservoir)
Air pressure in the bottle forces the water
from the bottle up into the DUWL and out
to the handpiece and air-water syringe
Self-contained water systems have two
advantages
Dental personnel can select the quality of
water to be used (e.g., distilled, tap, sterile)
Maintenance of the water system (between
the reservoir bottle and the handpieces and
syringes) is under the control of the dentist
and staff
Methods for Reducing
Bacterial Contamination
It is not yet possible to eliminate
biofilm, but it can be minimized with the
use of:
Self-contained water reservoirs
Chemical treatment regimens
Microfiltration
Daily draining and drying of lines
Chemical Agents
Chemicals can be used to help control biofilm
in two ways
Periodic or “shock” treatment with biocidal levels
(levels that will kill microorganisms) of chemicals
Continuous application of chemicals to the system
(at a level that will kill the microorganisms but not
harm human beings)
Always check with the manufacturer of the
dental equipment to determine which
chemical product and maintenance protocol is
recommended
Monitor water quality in the dental unit in
accordance with the manufacturer’s recommendation’s
Infection Control
and Dental Unit Water
Using the proper water
Dental unit water should not be used as an
irrigant for surgery involving the exposure of
bone
Only use sterile water from special sterile
water–delivery systems or hand irrigation
with sterile water in a sterile disposable
syringe
Minimizing Aerosol
Always use the high-volume evacuator
when using the high-speed handpiece,
ultrasonic scaler, and air-water syringe
The high-volume evacuator may also
reduce exposure of the patient to these
waterborne microorganisms
Flushing Waterlines
All DUWLs and handpieces should be
flushed in the mornings and between
patients
Although this will not remove biofilms
from the lines, it may temporarily
reduce the microbial count in the water
It will help clean the handpiece
waterlines of materials that may have
entered from the patient’s mouth
Flushing also brings a fresh supply of
chlorinated water from the main
waterlines into the dental unit
