E.J. Neiburger, DDS
In recent years it has become fashionable to decry the potential dangers of dental unit waterlines. Authors and bureaucrats have scurried to identify dangers lurking in the tubes and pipes of dental units. A few coincidental cases of Legionaires disease among dental patients and staff, out of billions of patient contacts, have focused the media and dentists on this otherwise non-problem.
The November issue of JADA featured "Dental Unit Waterlines: Approaching the Year 2000." It mentions continued concern over Legionella as the prime, potential source of water-related dental infections. I find it interesting that dentistry, unlike medicine, continues to produce faulty research focusing on the presence of "Legionella" microbes as a serious problem, which it is not. There are 23 species of Legionella and many more sub-species with only one - L. pneumophila, having been associated with serious illness.
Measuring harmless "Legionella" in waterlines and biofilm and equating this to disease risk is poor science. What researchers must do is to identify and measure pathogenic L. pneumophila - the agent that causes harm. Few authors/articles do this due to ignorance or the expense and difficulty in identification and isolation of this one type of Legionella among dozens of similar, but relatively harmless, Legionella microbes which do not produce endotoxin. If this were done, "Legionella" would appear as a miniscule problem.
Legionella (family Legionellacea) is a common and wide-spread group of organisms located in most water and soil samples. Around the time of the Mt. St. Helens volcanic eruptions, half of all air samples taken contained airborne Legionella.
Readers should be aware that the presence of garden-variety "Legionella" does not pose significant hazards to our patients. Large numbers of one particular variety, L. pneumophilia, do. I believe research and reports that fail to make this distinction but paint all Legionella with the same "toxic" brush are misleading, if not blatant, junk science.