1. Dental Unit Waterlines
Chapter 24
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2. Chapter 24 Lesson 24.1
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3. Learning Objectives Pronounce, define, and spell the Key Terms.
Discuss why there is a renewed interest in contamination of dental-unit waterlines (DUWLs).
Explain why DUWLs contain more bacteria than faucets do.
Identify the primary source of microorganisms in dental-unit water.
Explain the role of biofilm in DUWL contamination.
(Cont’d)
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4. Learning Objectives (Cont’d)
List the factors in bacterial contamination of dental-unit water.
Describe methods to reduce bacterial contamination in DUWLs.
Describe the recommendations of the Centers for Disease Control and Prevention (CDC) for dental-unit water quality.
Explain the CDC’s recommendation for the use of saliva ejectors.
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5. Introduction
Outbreaks of waterborne disease have occurred in a broad range of facilities. Although there is no evidence of a widespread public-health problem, published reports have associated illness with exposure to water from dental units. The fact that bacteria capable of causing disease in human beings are found in DUWLs is reason for concern.
(Cont’d)
The CDC recommends that dental water meet the same standards as drinking water.
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6. Introduction (Cont’d)
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 water, but the levels of bacteria found in the dental units are almost always higher.
Most organisms isolated from dental-water systems originate from the public water supply and do not pose a high risk of disease to healthy persons.
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7. 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.
What other pathogenic organisms are dental healthcare workers exposed to? (According to the CDC, Pseudomonas.)
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8. Microorganisms in Waterlines
The primary source of microorganisms in DUWLs is the public water supply.
Saliva can be retracted into DUWLs during treatment. This process is called “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 skyrockets.
How does biofilm function in the plastic tubing? (It serves as a reservoir that dramatically increases the number of free-floating microorganisms in water.)
Monitoring of dental water quality can be performed with the use of self-contained commercial test kits.
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9. Communities of Bacteria
There are two communities of bacteria in DUWLs:
One bacterial community exists in the water itself and is referred to as planktonic (free-floating).
The other exists in the biofilm attached to the walls of the DUWLs.
How does biofilm form? (Biofilm forms when bacteria adhere to surfaces exposed to water and begin to excrete a slimy gluelike substance.)
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10. Fig. 24-1 Close-up of a dental tube’s opening.
The small-bore tubing is ideal for the formation of biofilm.
What is the best-known biofilm? (Dental plaque.)
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11. Fig A, Magnification of biofilm formation on the walls of the tube. B, Cross-section of biofilm formation in DUWL. (Courtesy of Sultan Chemists, Inc, Englewood, NJ.) A B
Biofilm is responsible for diseases such as ear infection, bacterial endocarditis (infection of the inner surface of the heart and its valves), and Legionnaire’s disease.
Biofilm may also be responsible for a variety of nosocomial (hospital-based) infections caused by infections at surfaces of catheters, medical implants, wound dressings, and other medical devices.
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12. Fig. 24-3 Bacteria in biofilm taken from DUWLs. (Courtesy of Dr
Fig Bacteria in biofilm taken from DUWLs. (Courtesy of Dr. Shannon Mills, U.S. Air Force.)
Biofilm is highly resistant to antibiotics.
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13. Biofilm
Biofilm exists in all places where 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.
Have students name five pathogens or organisms identified in dental water. (Pseudomonas, Moraxella, Klebsiella, Legionella, Mycobacterium.)
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14. Fig. 24-4 Bacteria in biofilm dropping into waterlines
Fig Bacteria in biofilm dropping into waterlines. Some bacteria are planktonic and enter directly from the municipal water supply.
Biofilm is notorious for causing pipe plugging, corrosion, and water contamination.
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15. Methods of Reducing 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
The American Dental Association and CDC recommend flushing of DUWLs for several minutes each morning.
Handpieces should be flushed with air or water for 20 to 30 seconds between appointments.
Some manufacturers may recommend the installation of antiretraction valves to prevent oral fluids from being drawn into the DUWLs.
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16. Self-Contained Water Reservoirs
These systems supply air pressure to the water bottle (reservoir).
The 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.
Use of a self-contained reservoir eliminates the need for inflow of municipal water and permits the introduction of chemical agents to remove or inactivate biofilm.
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17. Fig. 24-5 Self-contained dental-water unit. (Courtesy of Dr
Fig Self-contained dental-water unit. (Courtesy of Dr. Ronald Johns.)
Self-contained water systems require clearance by the U.S. Food and Drug Administration (FDA).
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18. Fig Reservoir water bottles and lines on self-contained water systems must be cleaned and disinfected in accordance with the manufacturer’s instructions. The container under the water bottle will catch any solution drips. Note: The dental assistant is careful not to touch and contaminate the neck of the bottle. (Courtesy of Pamela Landry, RDA.)
Keep in mind that the water used on the patient is only as clean as the water entering the unit.
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19. Microfiltration Cartridge
A disposable inline microfiltration cartridge can dramatically reduce bacterial contamination in dental-unit water.
This device must be inserted as close to the handpiece or air-water syringe as possible.
It should be replaced at least daily on each line. The use of filtration cartridges combined with water reservoirs can ensure improved water quality.
The filter traps suspended organisms before they reach the surplus.
Filtration cartridges require FDA clearance.
Some filters also release germicides, which require U.S. Environmental Protection Agency registration.
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20. Fig The DentaPure cartridge releases 2 to 6 ppm of iodine as the water passes over it. The water delivered to the handpiece water, 3-way water syringe, and ultrasonic scaler is treated. The cartridges are changed every 40 days. (Courtesy of DentaPure, Fergus Falls, Minn.)
Microfilters reduce bacterial contamination of the water but do not affect the biofilm that colonizes DUWLs.
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21. 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 the water quality in the dental unit in accordance with the manufacturer’s recommendations.
Biofilm is extremely resistant to chemical destruction; therefore chemical treatments must be performed regularly, usually once a week.
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22. Water for Surgical Procedures
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.
Why is it important not to use dental-unit water during surgery? (Procedures such as periodontal surgery, root canals, and tooth extractions are riskier because they expose the gum line. Introducing dental-unit water could also introduce disease-causing bacteria.)
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23. 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.
Commercial devices and procedures designed to improve the quality of water used must be implemented to improve the quality of dental water.
Flushing will not remove biofilm from the lines; biofilm can form while water is moving through the lines.
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24. Minimizing Aerosols
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.
Why should the high-volume evacuator be used? (It will reduce contamination from the aerosol, spatter from the patient’s saliva, and contamination from the water spray.)
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25. Using Protective Barriers
The dental dam greatly reduces direct contact.
The dam also greatly reduces the aerosolization and spattering of the patient’s oral microorganisms onto the dental team.
Protective barriers, including masks, eyewear, and face shields, also serve as barriers for the dental team.
What is the purpose of the rubber dam? (It serves as a protective barrier for the patient against the dental-unit water.)
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