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   Publications specific to cross-contamination and backflow

  1. Patient to Patient Transmission of Hepatitis B in Dental Clinic.  CDC Report - October 2013.

  2. Backflow in low volume suction lines may lead to cross-contamination.  Chris Miller Ph.D.

  3. Cross-Contamination potential of saliva ejectors used in dentistry.  J. Barbeau, L. ten Bokum, C. Gauthier and A.P. Prevost

  4. Possibility of Cross-Contamination between dental patients BY MEANS OF THE SALIVA EJECTOR.  Whitehouse, RDH and C.M. Watson

  5. 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

  6. Hepatitis C Infections May Come From Routine Dentistry. Kate Foster, "The Scotsman"

1. Patient to patient transmission of Hepatitis b in dental clinic.

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.

Link to CDC Report on patient to patient Hepatitis B transmission in dental clinic.
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2. Backflow in low volume suction lines may lead to 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

Link to Dr. Chris Miller's article
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3. Cross-contamination potential of saliva ejectors used in 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

Link to PubMed Abstract
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4. Possibility of Cross-Contamination between dental patients BY MEANS OF THE SALIVA EJECTOR.

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

Link to PubMed Abstract
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5. Backflow in low-volume suction lines: THE IMPACT OF PRESSURE CHANGES.

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

Link to JADA Article
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6. Hepatitis C Infections May Come From Routine 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"

Link to the Kate Foster Article
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