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The healthy mouth is home to more than 350 species of
micro-organisms. Less than 5% of them are involved in periodontal
disease. Normally the harmful bacteria are kept in check by the
body's immune system and good oral hygiene. But in people
susceptible to periodontal disease, the harmful bacteria can take
over and begin the process that leads to gingivitis and
periodontitis. Researchers have shown
that increased levels of one species of bacteria called
Porphyromonas gingivalis doubles the risk for serious gum
disease. That same species in combination with one other appears
to cause periodontal disease in children and young adults.
The role of bacteria
Periodontal disease begins when harmful bacteria block the
antibodies and other anti-bacterial agents the immune system
normally sends out to destroy them. These types of bacteria are
then free to grow and reproduce. Once they are present in
sufficient amounts, they can turn the immune system of a
susceptible person upside down and inside out.
As the harmful bacteria proliferate, they invade the crevices
between teeth and gums. There they produce plaque, a soft, sticky substance that can harden and
form tartar (calculus). The bacteria
in plaque and tartar-release substances that trigger the immune
system. The immune system responds by mobilizing a variety of
immune cells, including macrophages, monocytes, lymphocytes, and
fibroblasts, at the site of the infection. This is a normal
response that usually helps get rid of an infection. But in
gingivitis it results in red, swollen, inflamed gums.
In periodontitis, bacteria go on to stimulate these
inflammatory immune cells to release a series of
infection-fighting substances called cytokines. The cytokines
that are produced are the kind that promote inflammation. One of
their many jobs is to signal other cells to come to the site and
release various substances. This increases the inflammation and
further damages the gums. Even worse, one cytokine signals a
certain type of cell to produce enzymes called matrix
metalloproteinases. These enzymes break down collagen in the
tissues around teeth. Collagen is a fibrous material that makes
up bone, cartilage, and connective tissue. Its destruction leads
to the creation of deep pockets in between teeth and gums, and
eventually the destruction of the structures that hold teeth in
place.
Other risk factors
Specific species of bacteria must be present for periodontal
disease to develop, but usually other risk factors must be
present as well. In fact, 80% of people with gum disease have at
least one other risk factor that makes them susceptible. Multiple
factors are frequently involved. For example, stress, poor diet,
smoking, and viral infections all play a role in acute
necrotizing gingivitis. When this was discovered in the 1990s, it
was good news. Because some of the risk factors are environmental
or behavioral, and thus could be changed, it meant that gum
disease might be preventable in some cases.
Aside from bacteria, age, poor dental hygiene, and poor
nutrition, the major risk factors are:
Genetics. Studies of identical twins, family
histories, and genetic diseases all point to heredity being a
risk factor in roughly 50% of patients with periodontal disease.
The heredity factors involved are most likely minor defects in
how the immune system operates. People with these abnormalities
cannot fight off the bacteria thought to be responsible for
causing plaque and periodontal disease even with good oral
hygiene. This may explain why children of parents with
periodontitis are 12 times more likely to have these harmful
bacteria.
Other family
factors. Researchers have found that the bacteria that
cause gum disease are in the saliva and can pass from one person
to another. Because of this, the American Academy of
Periodontology recommends that if one family member has
periodontal disease, all family members should be screened for
the disease. In the United States, African-Americans and
Mexican-Americans have a slightly higher risk of developing
periodontal disease than Caucasians. These groups also tend to
have more advanced disease. African-American and Mexican-American
males have the highest incidence. It's unclear whether
these differences are due to ethnicity or to such factors as
level of education and frequency of visits to the dentist.
Smoking. Smoking is
the number one environmental/behavioral risk for periodontal
disease. The more you smoke, the higher the risk and the more
severe the disease. Smokers are much more likely than non-smokers
to have tartar form on their teeth, have deeper pockets between
the teeth and gums, and lose more of the bone and tissue that
support the teeth. In fact, smoking can cause receding gums and
bone loss even in the absence of periodontal disease. Studies on
how smoking does its dirty work indicate that it has numerous bad
effects on the health of gum tissue and the workings of the
immune system. For example, smoking suppresses the production of
antibodies directed against some of the harmful bacteria, which
allows them to flourish more easily. Smoking also promotes
inflammation and increases bone loss. For these reasons, quitting
has become an important part of preventing and managing
periodontal disease.
Female hormones.
Anything that causes a changes in the level of female sex hormones (puberty, menstruation, pregnancy, menopause, and use of oral contraceptives) makes women more susceptible because such changes make the gums more sensitive to irritants and plaque. For example, when progesterone levels are high, say just before menstruation, the blood vessels in gums dilate, increasing inflammation. This is why some women experience flare-ups of gingivitis a few days before their period begins. Progesterone, present in oral contraceptives, also blocks the repair of collagen. At menopause, women may experience inflamed gums, oral pain, dry mouth, and abnormal tastes and sensations (salty, metallic, spicy, acidic, sour) in the mouth. In February 2000, the National Women's Health Resource Center issued a report called The Women's Guide to Oral Health as part of their "Brush Up On Wellness" campaign. It discusses gum disease in women and offers advice on preventing it.
Medical conditions.
Diabetes mellitus, osteoporosis, inflammatory bowel disease,
Down's syndrome, and AIDS are just some of the conditions that
make people more susceptible to periodontal disease. Studies have
shown that diabetes increases susceptibility and severity of gum
disease by impairing the function of certain immune cells and
decreasing the production of collagen and bone. Research now
shows that the relationship between the two diseases goes both
ways. Gum disease may make it more difficult for diabetics to
control their blood sugar. The loss of minerals from bones, seen in osteoporosis, is thought to make bones supporting the teeth more vulnerable to bacterial infection, increasing the risk of gum disease and tooth loss.
Medications. Susceptibility to gum disease can
also be caused by some medications, including steroids,
cyclosporine (an immunosuppressant), oral contraceptives (the
ones that contain the synthetic progesterone desogestrel),
Dilantin® (an anti-seizure drug), and Procardia® (or nifedipine, a
calcium channel blocker used to treat angina).
Stress and grinding/clenching
teeth. Emotional stress may increase your risk for
periodontal disease by depressing the immune system, making it
more likely for a bacterial infection to take hold. The
mechanical stress of grinding and clenching teeth exerts force on
the gums and other supporting tissues and may loosen your
teeth.
Obesity. According
to one recent study, obesity may also predispose a person to gum
disease.
Sources:
Albandar JM, Brunelle JA, Kingman A. Destructive periodontal disease in adults 30 years of age and older in the United States, 1988-1994. J Periodontol. 1999;70:13-29.
American Academy of Periodontology www.perio.org
American Academy of Periodontology, Committee on Research, Science, and Therapy. Informational Paper: the pathogenesis of periodontal disease. J Periodontol. 1999;70:457-470.
National Women's Health Report: The Women's Guide to Oral Health. National Women's Health Resource Center, Inc, February 2000.
Oliver RC, Brown LJ, Le H. Periodontal diseases in the United States population. J Periodontol. 1998;69:269-278.
Page RC, Offenbacher S, Schroeder HE, et al. Advances in the pathogenesis of periodontitis: summary of developments, clinical implications, and future directions. Periodontology 2000. 1997;14:216-248.
Reviewed Web Sites on Periodontal Disease
Want to learn more about periodontal disease? Then check out these articles in our Lifestyle forum:
Do You Have Periodontal Disease?
How Serious Is Periodontal Disease?
Treating Periodontal Disease
Dental Health Tips
What Is Periodontal Disease?
How to Brush Correctly
How to Floss Correctly
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