- It isn't just the dental drill you should be worried
- Oral water sprays used by dentists contain levels of
some bacteria that could kill vulnerable patients, government researchers
- They found that levels of opportunistic pathogens exceeded
EU drinking water safety limits in 52 out of 55 water samples taken from
21 dental surgeries in the south-west of England.
- This means people with weakened immune systems, such
as cancer patients and those with HIV infection, are at risk, the researchers
warn. James Walker of the Centre for Applied Microbiology and Research
at Porton Down and his team found several types of opportunistic pathogens
in many of the dental unit water lines (DUWs) tested, including species
of Mycobacterium and Legionella--both of which can cause life-threatening
- David Turner of the British Dental Association (BDA)
admitted to New Scientist: "People with compromised immune systems
- The researchers also isolated oral streptoccoci in 10
per cent of the samples. Since the bacteria is only found in the mouth,
it is most likely that during dental procedures it was sucked back into
the tools and into the DUW. Robert Staat of the University of Louisville's
school of dentistry has also found oral streptococci in DUWs. "This
is like sharing spit," he says.
- Normally, most of the bacteria breed- ing in DUWs occur
naturally in the environment and pose little threat to most people. Even
so, healthy patients shouldn't be exposed to these levels of bacteria when
they are at a healthcare facility, argues Hugh Pennington, a microbiologist
at the University of Aberdeen. "I wouldn't want to have these in my
- Walker's team found levels of bacteria between 5 and
1200 times higher than the permitted 2500 microbes per teaspoon of water.
Some of the highest bacterial counts came from DUWs that were either supplied
with bottled water or were recently sanitised. This casts doubt on the
effectiveness of recommendations by the BDA and its US counterpart, the
American Dental Association (ADA) that surgeries should use bottled water
and disinfectants to reduce the risk from bacteria.
- The ADA told New Scientist that similar studies carried
out in several US cities revealed bacterial counts that surpass its own
- Dentists in both the US and Britain are advised to use
sterile water for immune compromised patients and those receiving surgery
where the gum line is cut. But both the ADA and BDA admit it's not clear
how strictly this advice is followed.
- Despite the millions of people who visit a dentist each
year, contaminated dental water was blamed for only a handful of infections.
Although some patients died, the link to dental water was never proved.
- Source: Applied and Environmental Microbiology (vol 66,
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