#9 Dental Unit Waterline Asepsis Flashcards
What was the History of Dental Unit Waterline ?
- Contamination first reported (1963) by Dr. Blake in Great Britain
- Hand pieces cooled by separate water reservoir
What was the problem?
-Microbes colonize dental water lines forming biofilm leading to contaminated water & aerosols.
What are biofilms?
- Microbial colonies that adhere to solid surfaces in areas where there is sufficient moisture
- Portions of the biofilm break away, contaminating the water with high levels of bacteria
What are 3 examples of bacteria that can colonize the biofilms?
1) Pseudomonas aeruginosa
2) Staphylococcus aureus
3) Legionella species
What are 5 components of the biofilm?
1) Seeding dispersal
2) Rolling
2) rippling
3) streaming
4) detaching
What is the Safe Water Drinking Act set level (How much bacteria is present) for MUNICIPAL water ?
500 CFU/mL
Colony Forming Units
- What are the untreated DUQL levels ?
- What is the counts reported within 5 days of installation of new lines?
- 1,000-1,000,000 CFU/mL
- 200,000 CFU/mL
What is the bacterial population explosion every 20 minutes?
1 bacteria –> 8 a.m
4096–> 12 noon
134,217,728 –> 5 p.m
(contamination peaks at about 24 hrs)
Where do the bacteria come from?
1) The oral cavity
2) The waterlines
3) cross contamination
Where do the majority of microorganisms come from?
- The municipal water system
- Some come from anti retraction device failure
- There have been reported cases of cross contamination into the DUWL becomes of..
What is the Anti-Retraction Valve?
- Prevents back flow of fluid from patient into DUWL
- Failure allows retraction of fluid from patient #1 into the waterline, contaminating lines.
- Bacteria then delivered to patient #2
What are the characteristics of the DUW?
- Very small diameter 1/16” to 1/8”
- Very slow flow rate-drips/second
- Plastic tubing is hydrophobic (biofilm attachment)
- Tubing provides carbon for the bacteria
- Large surface area to volume ratio
- Interior surface is rough
- Left stagnant for hours
- Chlorine dissipates over 24 hrs
What are the characteristics of Tap Water?
- -1/2” diameter
- 5 L/min flow rate= 1000X dental flow
- Copper is antimicrobial & bacteriostatic
- Small surface area to volume ratio
- Interior surface is smooth
- Line is flushed w/ fresh water often
- Cholinated at every use
What is the DUWL-Surface colonization?
- Mineralized found in water are deposited on surface tubing
- Molecules in water help bacteria found in the water to adherer to these surfaces
- Overtime a micro colony is formed
What is the DUWL-Surface: volume?
-As the diameter of the tubing decreases, the surface area covered by biofilm increases. At the same time, the volume of water passing by DECREASES
What is an example of a Biofilm Disease?
Legionellosis (Water borne bacteria)
- Flu-liek symptoms called PONTIAC FEVER
- Pneumonia
-Two fatal cases in Legionellosis in dentists
(Dentists’ blood tested at 5% higher than vernal population= occupational exposure)
-Where can Legionnaries disease be traced?
- Bacteria can be traced to the air-conditioning/cooling system of the hotel
- Dental offices b/c of the right conditions
Legionnaries disease
S/S?
- When does it develop?
- How is bacteria carried?
-Develops 2-14 days after exposure to Legionella bacteria
- Headache, muscle pain, chills, fever of 104+
- Cough, shortness of breath, fatigue, loss of appetite, GI upset.
- **Affects primarily the lungs
- Bacteria carried in AEROSOLS of WATER VAPOR, not person-to-person.
- Environment for growth of Legionella
What are the ideal growth conditions for Legionella?
- Stagnation
- Temp = (95-115)
- pH = 5-8.5
- Sediment that tends to promote growth of commensal microflora
- Algae, flavobacteria, and Pseudomonas, which supply essential nutrients for growth of Legionella or harbor the organism (amoebae, protozoa)
What do studies show for L.pneumophilia compared to 8% of general population?
- 23% of dental staff working for > 2 yrs were antibody + for it compared to the 8% general population
- Exposure to endotoxins found in DUWL has been associated with onset of asthma in a subgroup of dentists
What is the Safe Water Drinking Act set level (How much bacteria is present) for Dental water ?
200 CFU/mL
Per ADA 1996
In 1993 CDC encouraged dentists to __________________ in the air-water syringe valve
Install anti-retraction devices
Does it make sense to sterilize a hand piece or ultrasonic tip, and run contaminated water through it?
No!
But instead:
-Flush water through the lines-temporary effect
-Independent reservoirs
-Chemically treat water (Regular tap water with tablet)
What is the Chemical Treatment?
- Chemicals include iodine, chlorine, ozone, chlorhexidine, silver, peroxides, & organic acids
- May be time-consuming and technique sensitive
- Potential incompatibility w. the dental equipment
