Source: http://jada.ada.org/cgi/content/full/137/suppl_2/5S
While
the practicing dentist always has had an appreciation for the
importance of oral health, research reports and articles in the lay
press during the past 25 years or so have done much to bring this to
the attention of our medical colleagues and the public at large. In
particular, the possibility that events in the oral cavity can
influence systemic disease has been highlighted by the U.S. surgeon
general’s report in 2000(1) and in numerous
reports of investigations into associations and interactions between
oral disease—particularly periodontal disease—and coronary heart
disease, stroke, adverse pregnancy outcomes, diabetes and bacterial
pneumonia.
The reported studies have included
epidemiologic studies, intervention studies and studies seeking to
elucidate mechanisms of action. Results of different studies have, at
times, been contradictory, which is not surprising given the variations
in study design, populations studied and statistical analyses used in
the plethora of reported studies. This, however, creates a dilemma for
those not intimately involved in this area of research. What are we, as
practicing dentists, to make of all this? What can we authoritatively
tell our patients in response to their inquiries regarding
relationships between oral and systemic diseases?
The
purpose of this supplement is to provide an update of the field that
will enable us to respond with the latest information to questions our
patients might ask.
FOCAL INFECTION THEORY
The
concept that oral conditions can significantly influence events
elsewhere in the body is not new, but it has undergone a number of
iterations over the years.(2–5) A frequently cited early publication is an 1891 report by Miller entitled "The Human Mouth as a Focus of Infection."(6) Miller was highly attuned to the role of bacteria in disease causation,
as he was working in the laboratory of Robert Koch, whose postulates
were used to establish the microbial etiologies of infectious diseases.
Miller proposed a role for oral microorganisms or their products in the
development of a variety of diseases in sites removed from the oral
cavity, including brain abscesses, pulmonary diseases and gastric
problems, as well as a number of systemic infectious diseases.
The
role of oral sepsis as a cause of systemic disease was championed by
William Hunter, a prominent British physician, in a publication(7) and a 1910 talk at McGill University, Montreal.(2)He
spoke, with considerable hyperbole, of dental restorations "built in,
on, and around diseased teeth which form a veritable mausoleum of gold
over a mass of sepsis to which there is no parallel in the whole realm
of medicine."(2)In 1919, Rosenow(8) published a series of animal experiments and human case reports
supporting the concept of focal infection. He emphasized the importance
of cooperation between dentists and physicians, as well as the
necessity of ensuring that the focus of infection is eliminated
completely, and he noted that tooth extraction by itself might not be
sufficient.
Much of the evidence presented in
support of the concept of focal infection proved, on closer inspection,
to be anecdotal or of questionable scientific merit. Nevertheless, it
became common practice to extract all endodontically or periodontally
involved teeth to eliminate any possible foci of infection, with the
expectation that this would prevent or cure a whole host of local or
systemic problems.
MORE SCIENTIFIC APPROACH
By
about 1930, the validity of the focal infection theory began to be
questioned, and investigators found, when they considered the available
real outcome data, that there was no clear basis for ascribing the
occurrence of much systemic disease to the presence of oral foci of
infection. As a result, the focus of dental practice changed such that
restorative dental procedures re-emerged as the mainstay of most dental
treatment plans. However, as a more scientific approach was applied to
investigating clinical problems, it became clear that, in fact, there
were situations in which oral bacteria could affect distant structures,
in particular the case of bacterial endocarditis in susceptible people.
Beginning
in the late 1980s, a series of publications regarding the association
between periodontitis and some systemic conditions, especially coronary
heart disease and, to a lesser degree, stroke and preterm birth/low
birth weight, captured the attention of the dental profession. In some
sense, this can be construed as a return to the theory of focal
infection. However, the response of the dental and medical professions
this time was considerably more measured than that in the early part of
the 20th century.
This is likely a result of
several factors: the greater sophistication in methods of scientific
investigation and statistical analysis, including an understanding of
the limits of epidemiologic studies in establishing disease causality(9);
a markedly enhanced understanding of the etiology and pathogenesis of
periodontal diseases and associated systemic diseases that permits an
assessment of the biological plausibility of putative interactions; the
availability of successful methods of treating periodontal disease and
endodontic lesions; and the recognition that bacteria could in some way
be responsible for diseases that heretofore had a rather uncertain
etiology (for example, evidence documenting the etiologic role of
Helicobacter pylori in the development of gastric ulcers—not an exact
analogy to be sure, but a useful one).
The investigation into oral-systemic disease connections is a rapidly advancing area of research.
In
considering the existing data, it is important to differentiate between
those data supporting an association between two diseases or conditions
and those indicating a causal relationship, so that the information can
be interpreted accurately. Although oral microorganisms from various
sites potentially could be associated with systemic disease, the
articles in this supplement focus on the connection between dental
plaque and periodontal disease and adverse pregnancy outcomes,
cardiovascular disease, bacterial pneumonia and diabetes, as well as
the methods by which the data are analyzed and the issues involved in
study design and interpretation.
Each article
presents the current state of the field, indicates questions remaining
to be answered and the studies needed to accomplish this, and provides
a brief summation that can guide dentists’ responses to patients’
inquiries. I need to emphasize that the investigation into
oral-systemic disease connections is a rapidly advancing area of
research, and that new information is constantly appearing in the
literature. As the field develops further, we can anticipate a time
when the vision set out in the surgeon general’s report will be
achieved, confirming that dental care and oral health play a key role
in helping to ensure the overall good health of our patients.
FOOTNOTES
Dr.
Barnett is a clinical professor, Department of
Periodontics/Endodontics, School of Dental Medicine, University at
Buffalo, The State University of New York. He also is the guest editor
of this supplement. Address reprint requests to Dr. Barnett at 112
Hidden Ridge Common, Williamsville, N.Y. 14221-5785, e-mail
"mlbgums@aol.com".
REFERENCES
1. U.S.
Department of Health and Human Services. Oral health in America: A
report of the surgeon general. Rockville, Md.: U.S. Department of
Health and Human Services, National Institute of Dental and
Craniofacial Research, National Institutes of Health; 2000. Available
at: "www.surgeongeneral.gov/library/oralhealth/". Accessed June 22,
2006.
2. William Hunter. Quoted
by: O’Reilly PG, Claffey NM. A history of oral sepsis as a cause of
disease. Periodontology 2000 2000;23:13–8.
3. Thodden van Velzen SK, Abraham-Inpijn L, Moorer WR. Plaque and systemic
disease: a reappraisal of the focal infection concept. J Clin
Periodontol 1984;11(4):209–20.
4. Newman HN. Focal infection. J Dent Res 1996;75(12):1912–9.
5. Pallasch TJ, Wahl MJ. The focal infection theory: appraisal and reappraisal. J Calif Dent Assoc 2000;28(3):194–200.
6. Miller WD. The human mouth as a focus of infection. The Dental Cosmos 1891;33(9):689–713.
7. Hunter W. Oral sepsis as a cause of disease. Br Med J 1900;1:215–6.
8. Rosenow EC. Studies of elective localization: focal infection with
special reference to oral sepsis. J Dent Res 1919;1(3):205–67.
9. Taubes G. Epidemiology faces its limits. Science 1995;269(5221):164–9.
The oral-systemic disease connection. An update for the practicing dentist
Relationship between periodontal disease and pregnancy complications
Periodontal infections and cardiovascular disease
Periodontal disease and diabetes
Challenges in interpreting study results
