COMMUNITY DENTISTRY:

ISSUES RELATED TO DENTAL UNIT WATERLINES

PREPARED BY:

1. NOOR AFIQAH BT MOHD NOOR 1071102

2. MUHAMMAD HAFIZUL AMIN BIN JIMAAIN 1071103

3. MUHAMMAD HADI BIN MOHD HANIFAH 1071104

OUTLINE

1. Introduction

2. Issues

2.1. Are the potential pathogens from dental unit waterlines a health risk for you as a

dental professional?

2.2. What type of patients that might be particularly at risk from contaminated waterlines?

2.3. What can you do to decrease the risk from contaminated waterlines?

2.3.1. Methods for reducing contamination

2.3.2. Latest recommendations regarding dental unit waterlines

3. Discussion

3.1. Method in reducing DUWL’s contamination had been practices in Universiti Sains

Islam Malaysia (USIM)

4. Recommendation

5. Conclusion

6. References

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1. Introduction

Effective infection control is one of the cornerstones of good practice and clinical

governance. Due to a combination of negative publicity and an increased scientific

knowledge of dental unit waterlines’ (DUWL) biofilms and their associated risks,

contamination of dental unit waterlines has become a prominent infection- control issue. The

perceived threat to public health from DUWL contamination comes from opportunistic and

respiratory pathogens such as Legionella spp (causative agent of the pneumonia,

legionnairs’ disease), Mycobacteria spp and Pseudomonads. These organisms can be

amplified in the biofilm to reach infective concentrations, with the potential for inhalation or

direct contamination of surgical wounds. (Pankhurst CL et al.)

Bacteria in a water line at a dental office in Italy are being blamed for the death of an

82-year-old woman who contracted Legionnaires' disease just days after receiving dental

treatment. It occurs on February, 2011, an 82-year-old woman was admitted to the intensive

care unit with fever and respiratory distress. She was conscious and responsive. Chest

radiograph showed several areas of lung consolidation. She had no underlying disease.

Legionnaires’ disease was promptly diagnosed by Legionella pneumophilia urinary antigen

test; a bronchial aspirate was taken for microbiological examination. Oral ciprofloxacin was

started immediately. Nevertheless, the patient developed fulminant and irreversible septic

shock and died 2 days later. All samples from her home were negative on culture, but those

from the dental practice were positive for L. pneumophila. Laboratory experiments

demonstrated genomic matching between L. pneumophila found in the patient's respiratory

secretion and the dental unit water line. Aerosolized water from high-speed turbine

instruments was most likely the source of the infection. (Maria LR et. al., 2012)

Biofilm and bacterial contamination of dental unit waterlines (DUWLs) was first

reported in the literature nearly 50 years ago. (Blake, 1963) The quality of water from DUWLs

is important not only to the patient, but also to dental health care personnel as these groups

are regularly exposed to water and aerosols generated from the dental units. (Liaqat and

Sabri, 2011) Biofilms are microscopic communities that consist primarily of naturally

occurring water bacteria and fungi. They form thin layers on virtually all surfaces, including

dental water delivery systems. These common microbes or germs accumulate inside things

like showerheads, faucets and fountains, and in the thin tubes used to deliver water in dental

treatment. (American Dental Association, 1999)

Bioaerosols generated from DUWLs has been shown as a potential source of indirect

infection to dental health professionals. (Szymańska and Dutkiewicz, 2008) Most of the

bacteria isolated from DUWLs are Gram negative bacteria which can produce endotoxin

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such as Pseudomonas aeruginosa and Legionnella pneumophilia. Pseudomonas aeruginosa

is a natural water-loving biofilm producer, that when aerosolized is almost confirmed to cause

pneumonia-like disease in elderly or immuno-compromized individuals. (Atlas et al., 1995,

Barbeau et al., 1996)

Legionella pneumophilia in the DUWLs is the most frequent cause of human

legionellosis as was the case of a dentist in San Francisco, USA, who became seriously ill

from the disease. (Atlas et al., 1995) The ADA, OSAP and the CDC have been working since

the mid 90’s to do research and make recommendations to improve the quality of dental unit

water.

2. Issues

There are few issues related to the dental unit waterlines, which are:

1. Are the potential pathogens from dental unit waterlines a health risk for you as a dental

professional?

2. What type of patients that might be particularly at risk from contaminated waterlines?

3. What can you do to decrease the risk from contaminated waterlines?

2.1. Are the potential pathogens from dental unit waterlines a health risk for you as

a dental professional?

Bacteria get into our dental system from the original source water. If the water that is

used in most dental units comes from the municipal (city) water supply; this is the main

source of the microorganisms. The Environmental Protection Agency (EPA) has set a

standard that municipal water must contain no more that a total of 500 CFU/ml (colony-

forming bacteria per milliliter) A colony-forming unit is defined as one bacterial cell or a small

number of bacterial cells and a milliliter are about ¼ of a teaspoon. In other words, ¼ of a

teaspoon of municipal water can have no more than 500 colony forming bacteria.

The problem is that even though municipal water enters the dental unit at less than or

equal to 500 CFU/ml, the water that exits the dental handpiece or air/water syringe may

contain as many as 200,000 cfu/ml. Counts greater than 1,000,000 CFU/ml have been

reported (OSAP, 2004). Studies have isolated as many as 32 different bacteria, 6 different

types of fungi, and 2 types of protozoa from dental unit water. In addition to municipal water,

contamination can also come from the hands of the worker or from retraction of fluids from

patient’s mouths. Sterile water being the only exception to that rule.

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Most of the bacteria come from retraction. This is why some units have higher

contaminations than others. It depends on who was seen in the chair and how badly the unit

is retracting. Retraction is the action that occurs when a water relay within the dental unit

shuts off and draws water back into the device. It is bad because if the level of retraction is

great enough, it will draw bodily fluids back past the handpiece that is being sterilized and

into the handpiece hose that is not.

2.2. What type of patients that might be particularly at risk from contaminated

waterlines?

Some microorganism in DUWLs are harmless and have low pathogenicity, others are

opportunistic microbes which can affect individuals who are immunocompromised.

Immunocompromised patients are as listed below:

Elderly patients

Smokers

Alcoholic patients

Organ transplant patients

Recipients of blood transfusions

Diabetes

Cancer

Autoimmune diseases

Chronic disorders

If we treat these immunocompromised persons with contaminated water, there is a greater

risk that they will become ill due to their compromised ability to fight disease. Since we may

not be aware of the immune status of some of our patients, it is especially important to stay

current and compliant with the recommendations of the agencies that advise the dental

profession. Although we are especially concerned for immunocompromised patients, all

patients are entitled to the highest quality of care. This care includes the maintenance of

dental unit water.

2.3. What can you do to decrease the risk from contaminated waterlines?

The dental unit water becomes stagnant inside the lines at several times; between

patients, overnight, on weekends, during lunch breaks. This intermittent stagnation of the

water allows the bacteria to grow and flourish on the walls of the waterlines. The four most

commonly discussed bacteria within biofilms of Dental Unit Water Line are Legionella

pneumophila, Mycobacterium spp., Pseudomonas aeruginosa, and Staphylococcus spp.

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Basically, there are two types of sources of water of Dental Unit Waterlines, which are

municipal water line and reservoir (bottle).

Below are the differences of dental unit water line compared to tap water line.

Dental unit water line Tap water line

Very small diameter 1/16”-1/8” ½” diameter

Very slow flow rate drips/sec 5 L/min flow rate (>1000x dental)

Plastic tubing is hydrophobic making

biofilm attachment easy. The tubing is

also a source of carbon for the bacteria.

Copper as a metal and as a dissociated

ion is antimicrobial/bacteriostatic

Large surface area to volume ratio Small surface area to volume ratio

Rough interior (extrusion molded) Smooth interior

Left stagnant for long periods Fresh every time turned on

Chlorine rapidly dissipates over 24

hours and can even be absorbed by the

tubing.

Chlorinated and replenished with every

use.

Below are the comparisons between distilled water and city water.

Distilled Water City Water

No Chlorine Chlorinated

No Minerals Calcium, Lime, Rust, etc.

Must be delivered or made onsite Dispensed out of tap

Not sterile Not sterile

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2.3.1. Methods for reducing contamination

1. Stop retraction. (Our Clinic Solutions)

Install an anti-retraction valve. It only allows the water to flow in one direction. Anti-

retraction valve can fail as with most leakage problems within a delivery unit, check

valves fail due to contamination from biofilm. Once this occurs, the check valve needs

to be replaced.

2. Self-Contained Water Systems

In order to comply with recommendations, it is necessary to install an independent

water supply on each dental unit. This unit can be filled with higher quality (distilled)

water than the municipal supply. It also allows for maintenance procedures that lower

the overall microbial count. It is impossible to comply with these recommended

protocols without a self-contained water supply. Remember that even sterile water in

the self-contained bottle will exit the waterline highly contaminated. Therefore,

surgical procedures should never be irrigated from a dental unit waterline, but from an

independent sterile water delivery system. The use of water heaters in dental units is

not recommended because they increase levels of bacterial colonization. The

maintenance of the water system is under the control of the doctor and staff.

3. Chemical Treatment Regimens

Consult with the manufacturer of the dental unit to determine the proper chemical

treatment. Some agents are placed in the bottles once a week, flushed through the

lines, and left overnight to decrease the biofilm. Others are added daily to the

treatment water to deliver continuous antimicrobial activity in the lines. Chemical

agents making antimicrobial claims should be registered with the EPA. There are a lot

of methods and chemicals available such as:

Dry flushing

Bleaching (5.25% sodium hypochlorite 1:10 ratio)

Filtration (iodine inline filters, clearline)

Sterilization (UV lights)

Shock treatments (Mint-A-Kleen, Sterilex)

Tablet in bottle treatments (BluTab, ICX)

Sterilizable water delivery tubings

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4. Microfiltration Cartridges

Disposable microfiltration cartridges can be used to decrease dental waterline

contamination. They should be inserted as close to the handpiece or air/water syringe

as possible. Most are replaced daily. They do not decrease the colonization in the

waterline, but filter the microbes before they exit the line into the patient’s oral cavity.

Therefore, filters are often used in combination with antimicrobial agents.

5. Weekly Waterline procedures

Remove the self-contained water bottle and empty. Weekly, place the recommended

amount of cleaner into the bottle, reconnect, turn unit on to pressurize, and flush line

until you see the cleaner coming through the line. Leave for the recommended time

period, usually overnight. The next morning, flush all the cleaner through the line.

Remove the bottle and fill with high quality water (distilled), flush all the water through

the line to remove all the cleaner from the lines. Do not touch the tubing that goes into

the bottle. Refill with water.

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2.3.2. Latest recommendations regarding dental unit waterlines

Guidelines for Properly Treating Dental Unit Waterlines (Updated September 2004).

1) Follow current ADA and CDC recommendations to flush handpiece hoses and air/water

syringes for 20-30 seconds between patients. Also, if recommended by the dental unit

manufacturer, install and maintain antiretraction valves to prevent oral fluids from being

drawn into dental waterlines.

2) Do not heat dental unit water. Warming the water promotes biofilm formation.

3) Consider implementing equipment and procedures that have been shown to improve the

quality of water such as separate reservoirs, chemical treatment protocols, and sterile

water delivery systems.

4) Use a separate water reservoir system to eliminate the flow of municipal water into the

dental unit. This allows better control over the quality of source water for patient care, and

eliminates interruptions in dental treatment when local health authorities issue boil-water

notices. Contact the manufacturer of the dental unit for recommendations for a

compatible system and treatment protocols before purchasing.

5) Use sterile solutions for all surgical irrigations.

6) Educate and train all dental health-care personnel on effective treatment measures to

ensure compliance and minimize risks to equipment and personnel.

7) Follow recommendations for monitoring dental unit water quality provided by the

manufacturer of the unit or waterline treatment product to assess compliance with

recommended protocols and identify technique errors or noncompliance. In the absence

of manufacturer's instructions, monitor dental unit water quarterly.

8) Monitor scientific and technological developments to identify improvements as they

become available.

9) Ensure that sterile water systems and devices marketed to improve dental water quality

have received FDA clearance.

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3. Discussion

1. Not every student practices the daily protocol as it is not being highlighted so well.

2. Daily and weekly routine must be done by student with the supervision of supervisor.

3. A written instruction or protocol should be provided as a guidelines or checklist.

3.1. Method in reducing DUWL’s contamination had been practices in Universiti

Sains Islam Malaysia (USIM)

The faculty have strict specification upon buying the dental chair with the technologies

to reduce water contamination. Features such as anti-retraction valve must be included.

A study had been done by the lecturers of USIM regarding the microbial contamination level

of water supply system at the faculty found out that the quality of water supplied at the

Faculty of Dentistry, USIM was within the limits recommended by the ADA which is the

bacterial loads of not more than 200 cfu/ml for dental procedures.

The students before starting their clinical session had being taught by the dental

technicians regarding the safety and protocols upon handling the dental chair and its

equipments such as the handpieces. Following the protocols by agencies should aids in

reducing the contamination of DUWL’s such as the recommended protocols by CDC on

2003:

1. Consult with the dental unit manufacturer for appropriate methods and equipment.

2. Follow manufacturer’s directions for monitoring water quality

3. Discharge water and air for a minimum of 20 to 30 seconds after each patient from any

dental device connected to the water system

4. Consult with the manufacturer on the need for periodic maintenance of anti-retraction

mechanisms.

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4. Recommendation

If the students being approach with patient asking regarding the DUWL’s, here are

some guidelines in explaining the issue of dental unit waterlines to patients in an easy-to-

understand and non-threatening manner.

1) Dental unit waterlines are small tubes (pipes) that deliver water to equipment such as the

high-speed handpiece (drill), air/water syringe and ultrasonic scaler [point out these

devices in the operatory]. During certain dental procedures, water is used to cool the

equipment and to flush away debris. It is also used with ultrasonic instruments to remove

calculus (tartar) and stain from teeth.

2) When water is used during a dental procedure, suction is used to vacuum up the water

and debris.

3) Microorganisms (germs) that are found in domestic water supplies can contaminate

dental unit waterlines.

4) Any surface that is exposed to water for a long period of time can develop a biofilm

(organized layer of germs and their products). This problem is common wherever water is

delivered through small pipes or tubes, like in the dental units.

5) Microorganisms (germs) found in dental unit waterlines pose a negligible threat to the

public and dental team. At present, there are no studies that show increased health risks

to dental patients from this water.

6) The bulk of microorganisms (germs) should not cause disease in normal, healthy

individuals, but may lead to illness in medical compromised patients (those with a weak

body defense system).

7) There are several options to lessen the problem and reduce the risk in dentistry. Some

are flushing the waterlines at the beginning/end of the day and between patients, using

independent water reservoirs and point-of-use filters, and chemically treating the

waterlines.

8) Explain to the patient exactly what your clinic does to address the issue.

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Here are also the flow chart to ease the students and the dental assistant as for their daily

protocol in reducing the contamination (Ma Mei Siang, 2012):

1) During each day, flush lines 20 to 30 seconds between every patient.

2) In the evening, empty the water from the bottle, places the bottle back on the unit, and

flushes all the remaining water out of the lines. Remove the bottle and leave off the unit

overnight to dry. The rationale for this procedure is that colonization of microbes is

decreased in a dry environment.

3) The next morning, place a clean bottle containing treatment water on the unit and turn on.

4) Flush the line for 2 to 3 minutes prior to seating the first patient. Flushing the line is not

considered a water quality control measure. It helps to clear stagnant water from the lines

and continues to be recommended at this time.

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5. Conclusion

DUWL is not a public health concern as it is not wide spread. Therefore, we do not

have to explain it to the public unless we are being asked. Contamination of DUWL is

universal. It is difficult if not impossible to eradicate the biofilm in these tubing and prevent its

regrowth. Nevertheless, every attempt has to be taken to minimize the contamination of the

tubing in order to maximize the health of the dental health care personnel and the patient.

Although the number of published cases of infection resulting from exposure to water from

contaminated DUWLs is limited, there is a medico-legal requirement to comply with potable

water standards and to conform to public perceptions on water safety (Sehulster and Chinn,

2003)

Dentists are encouraged to follow manufacturers’ instruction in maintaining the

DUWLs and use disinfectant whenever possible. Until ideal guidelines for maintaining

DUWLs is released by a professional body, flushing water for 20-30 seconds before starting

the morning session and in between patient treatments, remains the most economic way of

reducing bacterial load in DUWLs.

Most of the microorganisms found in DUWL are Gram negative, heterotrophic

bacteria that have little potential to cause disease in immunocompetent people. However,

immunocompromised patients and occupational exposed staff members may be at risk of

infection by such microorganisms. Owing to the multiple ports of entry of microbes to the

DUWL system, at present no single method or device completely eliminates biofilm formation

in the waterlines.

We must follow the safe water guideline as instructed by the authorities below.

• CDC (Center of Disease Control & Prevention) - For routine dental treatment, meet

regulatory standards for drinking water. <500 CFU/mL of heterotrophic water bacteria.

• ADA – Encourages industry and the research community to improve the design of dental

equipment so that by the year 2000, water delivered to patients during nonsurgical dental

procedures consistently contains no more than 200 CFU/ml at any point in the time in the

unfiltered output of the dental unit.

• EPA (Environmental Protection & Agency) - The number of bacteria in water used as a

coolant/irrigant for nonsurgical dental procedures should be as low as reasonably

achievable and, at a minimum, <500 CFU/mL

• OSAP (Organization for Safety,   Asepsis and Prevention) - The regulatory standard for

safe drinking water of <500 CFU/mL

• APHA (American Public Health Association) - the regulatory standard for safe drinking

water of <500 CFU/mL

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• AWWA (American Water Works Association) -the regulatory standard for safe drinking

water of <500 CFU/mL

• European Union Drinking Water Standards specify a maximum of 100 CFU/mL

Combinations of currently available procedures and equipment, including anti-

retraction devices, flushing, independent water supplies used in conjunction with biocide

purges or fully autoclavable waterline circuitry should provide water that is of a standard

higher than that of drinking water. However, all these systems require strict adherence to

maintenance protocols to perform to their full potential.

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6. References

1. American Dental Association (ADA) (1999). Dental unit waterlines: approaching the

year 2000. ADA Council on Scientific Affairs. J Am Dent Assoc, 130(11): 1653-1664.

2. Atlas RM, Williams JF, Huntington MK (1995). Legionella contamination of dental-

unit waters. Appl Environ Microbiol, 61(4): 1208-1213.

3. Adec’s Systems Guide, Publication No. 85-0801-00

4. Barbeau J, Tanguay R, Faucher E, Avezard C, Trudel L, Côté L, Prévost AP (1996).

Multiparametric analysis of waterline contamiantion in dental units. Appl Environ

Microbiol, 62(11): 3954-3959.

5. Blake GC (1963). The incidence and control of bacterial infection of dental units and

ultrasonic scalers. Br Dent J, 115: 413-416.

6. Liaqat I, Sabri AN (2011). Biofilm, dental unit water line and its control. Afr J Clin

Exper Microbiol, 12(1): 15-21.

7. Martin MV. The significance of the bacterial contamination of dental unit water

systems. Br Dent J 1987;163:152-4.

8. Ma Mei Siang et. al. The microbiological quality of water from dental unit waterlines in

Malaysian Armed Forces dental centres. Arch Orofac Sci (2012), 7(1): 7.

9. Maria LR, Stefano F, Federica P, Emanuela F, Maria FP, Paolo F, et. al.. Pneumonia

associated with a dental unit waterline. The Lancet. 2012 Feb 18-24, Vol. 379:9816,

p. 684.

10. Mills SE. The dental uni t water l ine controversy: defusing the myths, defining the

solutions. J Am Dent Assoc 2000;131:1427-41.

11. Sehulster L, Chinn RY; CDC; HICPAC (2003). Guidelines for environmental infection

control in health-care facilities. Recommendations of CDC and the Healthcare

Infection Control Practices Advisory Committee (HICPAC). MMWR Recomm Rep,

52(RR-10): 1-42.

12. Szymańska J, Dutkiewicz J (2008). Concentration and species composition of aerobic

and facultatively anaerobic bacteria released to the air of a dental operation area

before and after disinfection of dental unit waterlines. Ann Agric Environ Med, 15(2):

301-307.

13. Julian Holmes. Dental Unit Water Lines (DUWL’s) – A Review of The Problem &

Solutions. Retrieved from http://www.the-o-zone.cc/HTMLOzoneF/pdf/DUWL0207.pdf

on 1st April 2012.

14. Pankhurstn CL, Johnson NW, Woods RG. Microbial contamination of dental unit

waterlines: the scientific argument. Int Dent J 1998;48:359-68

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15. USAF Dental Evaluation & Consultation Service. Retrieved from

http://airforcemedicine.afms.mil/idc/groups/public/documents/afms/ctb_109865.pdf on

1st April 2012.

16. Caroline LP. Risk Assessment of Dental Unit Waterline Contamination. Retrieved

from http://www.sterilox.com/PDFs/Pankhurst_Paper_RiskDUWL.pdf on 1st April

2012.

17. OSAP. Retrieved from http://www.osap.org/?page=Issues_DUWL_1 on 1st April 2012.

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