Causes and Risk Factors of Periodontal Disease
The healthy mouth is home to more than 350 species of microorganisms. Less
than 5 percent 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 overcome 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.
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 fibroblasts (connective tissue cells) and a variety of immune
cells -- including macrophages, monocytes and lymphocytes -- to the site
of the infection. This is a normal response that usually helps get rid
of an infection. But the infection and immune response can cause gingivitis
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.
These cytokines t 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 is a constituent of bone, cartilage and connective
tissue. Its destruction produces deep pockets in between teeth and gums
and eventually destroys 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 percent 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.
Aside from bacteria, age, poor dental hygiene and poor nutrition, the
major risk factors are:
Genetic factors. Studies of identical twins, family histories and genetic
diseases all point to heredity as a risk factor in roughly 50 percent
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 responsible for causing
plaque and periodontal disease even with good oral hygiene. Such heredity
factors may explain why children of parents with periodontitis are 12
times more likely to harbor 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 (so never share your
toothbrush or use someone else's). Because of this, the American Academy
of Periodontology recommends 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 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.
Anything that causes a change 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. The 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. 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.
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 show 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 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.
Susceptibility to gum disease also can 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). If you are worried about this, talk to
your doctor. You should never stop taking a prescribed medication on your own.
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.
Sometimes a mouth guard worn during sleep is necessary.
According to one study, obesity may also predispose a person to gum disease.