Infection Control in Dentistry

Breaking the Chain of Infection
Things to think about
Potential pathogen in sufficient numbers
Susceptible host
Portal of entry
The susceptibility of the host and the pathogenicity of the microorganism- We have the least control of these.
Focus on reducing number of organisms in the clinical environment

Targeting reduction of numbers of potential pathogens
Surface Disinfection
Instrument sterilization
Hand washing
Antimicrobial mouth rinses – might select for resistant organisms
Quality of dental treatment water
Air quality

TB patients must be treated in the hospital with special air vaccums
Not too many offices are checking for air quality

Procedural errors that can cause sterilization failure
Improper operation time/temperature; proper water level
Easily remedy – Can control, just teach your staff to pay attention
Frequently associated with new operators or new instruments

Mechanical Problems that can cause sterilization failure
Must take out of service
Repair down time

Mechanical monitoring for sterilization
Record cycle time
Record temperature and pressure

Chemical indicators (e.g. indicator tape) for sterilization
Use with each instrument load
Failure of the indicator to change color- not exposed to proper sterilization environment- instrument load should be re-sterilized
Sterilizer specific (steam vs. chemical vapor)
Should not replace biological indicators

Biological indicators
for sterilization
Bacterial endospores that are highly resistant to heat
Only way to measure the microbial killing power of the sterilization process
ADA and CDC recommend weekly monitoring with biological indicators
NC Dental Board requires weekly monitoring with biological indicators
Offices send their spore strips to david arnold to make sure that things are working MAKE SURE YOU HAVE BACKUP AUTOCLAVE

Biological Indicator Procedure
Weekly required- more frequent might be justified- early discovery.
Biological monitoring- two ways
In-office incubator and spore monitoring strips
Mail-in spore monitoring programs- UNC Sterilizer Monitoring Service
Positive spore test indicates sterilization failure
Maintain a log of spore test results

Sterilization Failure
Take the sterilizer out of service
Review sterilization process to rule out operator error
Correct any identified procedural problems
Retest using biological, mechanical and chemical indicators
If no procedural errors identified or failures persist- DO NOT USE sterilizer until fixed!
As possible, reprocess all instruments sterilized since last negative spore test
Record positive test results and all actions taken to ensure proper function in monitoring log.

Why Record positive test results and all actions taken to ensure proper function in monitoring log?
If you don’t do this… and someone gets a disease.. Be sure you can show what you’ve done!

LIFE LESSON: BEFORE YOU STERILIZE… make sure you’ve gotten
the GUNK off.. This is super important because if there is
debris, then the area under the debris may not be sterilized!!!

Notification of Positive Test
Examine cultures daily
Gram stain confirms true positive
Early positive
Confirm control
Phone or fax ASAP
Immediate follow-up test

Dental Unit Water Lines
think biofilm build up in waterline

Waterborne Biofilms and Dentistry
Dental hand pieces (specifically high-speed drills)
Air/water syringes
Ultrasonic scalers
Small-bore plastic tubing

Water column moves through small lumen in center of tubing
Leaves thin layer of liquid undisturbed
Stagnation and warmth promote tenacious adherent microbial communities = biofilm

Biofilm formation
Grrowth – hard to remedy by now

Contamination levels in DUWL
Virtually all untreated water lines have significant recoverable microorganisms
Potable water: <1 fecal coliform/100ml and <500 colony-forming units (CFU)/ ml Water delivered from dental hand piece often >200,000 CFU/ml

Opportunistic pathogens:
Pseudomonas aeruginosa, Legionella pneumophila, non-TB mycobacteria, Acanthamoeba spp.

Risk of Infection from DUWL
Few substantiated links
1987- two cases of P. aeruginosa infections in medically compromised patients
1994- dentist died from pneumonic legionellosis
Isolated cases of amoebic eye infection, brain abscess and GI disorders
2007- link of Legionella pneumophila infections in NC

Four ways of infection from DUWL
Hematogenous spread during surgical procedure
Local mucosal contact

Dental Unit Water Lines series of events to infection possibilities
Pseudomonas- pioneer colonizer
Increasing incidence of isolation of enterics and Pseudomonas from gut
Peri-implant infections due to contaminated water line
Possibility of coming from treatment water
Monitoring of dental unit water lines
Requirement for regular disinfection

Evidence for Exposure
Prevalence of antibodies to L. pneumophila in dental personnel (34%) vs. controls (5%)
Nasal flora of dental personnel have a higher proportion of waterborne Pseudomonas spp.
Presence of waterborne bacteria in the air of dental clinics- no hard evidence
Theoretical risk of infection from DUWL

Potential Solutions
Distilled or sterile water does not solve problem
Mechanical flushing alone does not work- organisms continue to break free during procedure
Self-contained water systems vs. municipal supply
Filters: physical barrier- some impregnated with iodine
Autoclavable systems
Chemical products (disinfectants): some are corrosive, FDA approval, EPA approval, periodic vs. continuous, compatibility with various dental materials

ADA and CDC Recommendations
1995- <200 CFU/ml (same as kidney dialysis) 2000- <500 CFU/ml (potable water standard) UNC School of Dentistry- <200 CFU/ml Sterile water for surgical procedures Periodic water testing recommended if treatment protocol is in place

UNC Dental Unit Water Line Testing
Fixed volume of water collected at time of greatest possibility of contamination (Just before next treatment).
Tablet to neutralize chlorine
Specifically designed collection containers and shippers
Agar medium on quantitative paddles
48-72h at room temperature for growth
Quantitation of recoverable bacteria

Clinical Microbiology of Oral-Facial Infections
Most infections are from oral sources
Oral cavity is very septic environment
Dental plaque is comprised of bacteria and bacterial products and thus is equivalent in density to a bacterial colony on an agar plate.
Most pathogens of oral lesions are considered to be normal oral flora by hospital laboratories or are anaerobes that they cannot grow or identify

Indications for culture & antibiotic sensitivity testing.
Rapidly spreading infection
Postoperative infection
Non-responsive infection
Recurrent infection
Best to take culture samples before beginning antibiotic courser

Methods for identification of bacteria
Polymerase chain reaction (PCR).
16S RNA.
DNA-DNA hybridization.
Serological identification.

What’s the point of culture bacteria?
isolation, identification and determination of antibiotic sensitivities. Also can preserve isolate for subsequent determination of virulence properties.

UNC School of Dentistry Clinical Microbiology Laboratory
CLIA certified
One of only a few laboratories in the country that cultures and identifies oral pathogens including anaerobes
Receive samples from all over the country
Require rapid processing and express shipping in specialized transport media

Isolation and Identification by Colony Morphology

Antibiotics are critical tools in infection control. Culture, identification and determination of antibiotic sensitivities are frequently essential for responsible treatment with antibiotics.

What is the purpose of antimicrobials?

Murrah skipped

To limit the infection.
Control systemic involvement.
Impair accessible, susceptible bacteria to allow defenses to act.
Cannot substitute for clinical treatments.

Antimicrobial therapy
Murrah skipped
Aims to treat infection with drug to which pathogen is sensitive
Empirical antibiotic therapy- best guess
Knowledge of infectious disease
Most probable pathogen- Gram stain
Usual antibiotic sensitivity pattern
Rational antibiotic therapy
Culture and sensitivity
Kirby-Bauer vs. E-test (others)

Antibiotic Sensitivities Kirby-Bauer vs. E-test
plate with small antibiotic punched circles vs a strip of antibiotics

Methods for identification of bacteria

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