Clinical Research
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Patient to
Patient Transmission of Hepatitis B in Dental Clinic. CDC Report
- August 2007.
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Backflow in low volume suction lines may lead
to cross-contamination. Chris Miller Ph.D.
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Cross-Contamination potential of saliva
ejectors used in dentistry. J. Barbeau, L. ten Bokum, C.
Gauthier and A.P. Prevost
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Possibility of Cross-Contamination
between dental patients BY MEANS OF THE SALIVA EJECTOR.
Whitehouse, RDH and C.M. Watson
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Backflow in low-volume suction lines:
THE IMPACT
OF PRESSURE CHANGES. Ginger L. Byrd Mann, RDH, BS, MS, Tamara L. Campbell, DMD,
James J. Crawford, M.A., PhD
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Hepatitis C Infections May Come From
Routine Dentistry. Kate Foster, "The Scotsman"
In August of 2007, the Center for
Disease Control published a report regarding patient
to patient transmission of Hepatitis B (HBV) in a Dental Office. In 2001, a patient was diagnosed with Hepatitis B after
undergoing surgery at a dental office. The clinic had
previously performed dental surgery on another patient with
Hepatitis B. Molecular epidemiologic techniques indicated
transmission of HBV between the two patients.
When investigators visited the dental office, they found the
dental office followed standard infection control techniques.
All of the staff had been vaccinated for Hepatitis B and none had
HBV at the time of the patient surgery. The actual source of
the cross-contamination was not identified by the CDC. Even if
the standard infection control procedures were followed, the saliva ejector may have been the source of the cross
contamination.
Studies confirm a chance of cross-contamination from low volume
saliva ejector systems. The low-volume evacuation systems at
dental units were disinfected and a red solution was aspirated into
the suction line. Each test subject closed their lips around
the tip. The ejector tip was observed for the presence of red
dye coming back up from the vacuum line. The test was
performed 97 times with 15 dental units at nine locations.
The results indicated that backflow into a patient's mouth may
occur about 21 percent of the time when patients close their lips
around the saliva ejector tip to evacuate their mouth. The same
study confirmed that microbes can be recovered from the fluids
present in the low-volume vacuum suction lines. All the lines
were contaminated with colony forming units of bacteria. An
investigation determined 91 percent of 117 dental offices asked
patients to close their lips around the saliva ejector tip.
A second study was done to investigate the same
cross-contamination issue. A high-volume evacuator was used
simultaneously with the low-volume ejector. Test subjects
closed their lips around the saliva ejector tips. The study
concluded that a sudden drop in vacuum line pressure can cause the
backflow of fluids in the saliva ejector tip.
Based on these studies and personal communication with dental
manufacturers, it appears that a newly recognized mode of potential
cross-contamination has been discovered. Chris H. Miller, B.A,
M.S., Ph.D, Indiana University, School of Dentistry
Medical and Dental suction systems can lead to nosocomial
infections either by producing aerosols that contain potential
microbial pathogens or by supporting the growth of biofilms that
serve as an environmental reservoir of pathogenic micro-organisms.
The direction of flow in saliva ejectors was monitored while
volunteers closed their lips on the disposable mouthpiece.
During the tests, several reversals were recorded.
The reversal events occurred mainly when the mouthpiece was pressed
against the oral mucosa (cheeks or floor of the mouth). The
amplitude of flow oscillations was greatest when larger volumes of
saliva were aspirated, such as after the patient's mouth was rinsed
with water.
The pressure readings performed in the study show that flow
reversal happens in the saliva ejector. Closing the mouth
on the mouthpiece is not the only condition that creates backflow
and the risk of cross-contamination.
The study has demonstrated the relatively high probability that
fluid backflow episodes can occur from the saliva evacuation system
into the patient's mouth. Biofilms can serve as a reservoir
for micro-organism or may trap potentially infectious material such
as human cells and tissue for an undetermined period of time. J.
Barbeau, L. ten Bokum, C. Gauthier and A. P. Prevost, University of
Montreal, Department of Dental Medicine
A study of saliva ejectors by Dr. R.L. Whitehouse and C.M. Watson, identified the high potential for backflow problems and
the risk of cross-contamination at the treatment site. The
same study found organisms of oral origin in all vacuum lines they
tested. When vacuum pressure is released or reduced, backflow
(suck-back) can occur, exposing patient to the blood, saliva and
bacteria from previous patients.
Whitehouse and Watson added red dissolving solution to suction
lines that had been disinfected with a strong bleach/water solution.
When patients were instructed to
make a seal around the tip, 20 cases of red dye aspiration were seen
out of 97 tests involving 9 locations.
Whitehouse and Watson found 91 percent of dental offices they
surveyed instructed patients to close their mouth around the suction
tips, raising the likelihood for suck-back. They also
discovered only 41 percent of clinics surveyed rinsed or disinfected
the suction lines once a day. In light of these findings, the
study concluded that it is likely that some patients will aspirate
debris and bacteria when their lips create a seal by closing around
the ejector tip. R.L. Whitehouse, RDH and C.M. Watson,
University of North Carolina, School of Dentistry
Backflow from saliva ejector tubing into a dental patient's mouth
may serve as a source of cross-contamination. It could expose
the mucosa or non-intact tissue of a patient to previously suctioned
fluids such as saliva or blood components from another person
In three repetitions of 30 tests each backflow was observed 83 of 90
times when the tubing was positioned at the level of or above the
simulated mouth and when oscillations were produced by operating
other suction equipment. Ginger L. Byrd Mann, RDH, BS, MS,
Tamara L. Campbell, DMD, James J. Crawford, M.A., PhD, University
North Carolina, School of Dentistry
Although intravenous drug use is the most common method of transmission, health
workers say dental practices could be the source of infection for a "substantial number"
of the 38 percent of sufferers for whom the source of infection is not known.
In Scotland, 10,000 people are known to be infected with the disease, which can cause
liver disease and cancer and is 100 times more infectious than HIV. But because sufferers
can live for 20 years before showing any symptoms, experts believe that a further 25,000
Scots are unknowingly infected. Jeff Frew, the secretary of Capital
C, an Edinburgh-based support group for sufferers, said many people
do not know how they became infected and he believes there is a risk
of infection from dentists' tools. His claims have been backed by
Nigel Hughes, the chief executive of the British Liver Trust, who
said the risk of infection from dental surgeries "could not be
ignored."
Mr. Frew said, "Many of our Hepatitis C clients do not fall into any of the risk categories
for catching the infection. Dental treatment is the only time when members of the public
come into contact with blood and there's a huge throughput of patients receiving dental
treatment every day." Mr. Hughes said: "One problem lies with the mechanical dental handpiece
which sucks fluid, including blood and other matter, from the mouth". After treatment, if
the dentist adheres to guidelines, it is flushed through very rigorously and left to rest
for some time. "It would be possible to catch Hepatitis C in this way if the equipment is
not rigorously cleaned and sterilized. There's always a distinct possibility, especially if
the dental practice session is very busy." Kate Foster, "The Scotsman"
