Genetic Considerations of Diseases and Disorders that Affect the Oral Cavity
Part I. Overview, Dental Decay, Periodontal Disease, Diabetes
Almost every disease and disorder that affects the oral cavity (the mouth) has a genetic component. Even the most common oral diseases - tooth decay and gum disease - have hereditary influences. Both tooth decay (dental caries) and gum disease (periodontal disease) show various clinical symptoms and seriousness among individuals who otherwise practice similar oral hygiene habits. One reason why symptoms are so variable is that individuals inherit different degrees of genetic susceptibility or resistance to germs (bacteria) found in the mouth. Other diseases and disorders that can directly or indirectly affect oral tissues include metabolic diseases (such as diabetes), cancers of the head and neck, and developmental defects (like cleft lip and cleft palate).
ANATOMY OF THE
OF THE DENTAL EXAMINATION
WHAT IS THE
DENTIST LOOKING FOR WHEN PERFORMING
AN EXAM OF THE ORAL CAVITY?
Disease processes of the soft tissue of the cheek, lips, palate and tongue may also show surface changes when compared to healthy tissue. Surface changes may include ulcerations or erosion of tissue, tissue growth or swelling, changes in tissue color, and changes in tissue texture.
Why some individuals are more susceptible to dental decay than others is unclear. The structure of enamel proteins, the quality and quantity of saliva, and immune defense mechanisms against bacteria are all possible causes of susceptibility, and each has a genetic component. It is well understood, however, that prevention of dental decay is dependent on good oral hygiene, use of fluorides, and frequent professional health care.
Many medications compromise good saliva production by causing "dry mouth." Some of the 400 or so medications that cause the dry mouth side-effect are antihistamines and decongestants (taken for cold and allergy symptoms), antihypertensive medications (taken for blood pressure regulation), and medications taken for depression. One of the unfortunate side effects of radiation therapy for cancers of the head and neck is destruction of salivary gland tissue, which results in dry mouth and subsequent dental decay.
The first stage of periodontal disease is called gingivitis, or inflammation of the gums. Gingivitis is characterized by redness, bleeding, and swelling of gum tissue (gingiva). Without good oral hygiene, gingivitis can become a chronic infection that may progress into the more severe form of periodontal disease known as periodontitis. Periodontitis is a disease that involves both the gum tissue and supporting bone. The destruction of bone results in the formation of a pocket or space between the tooth and adjacent tissue. Such pockets contain bacteria that can continue and worsen the disease process. Destruction of supporting tooth tissues can lead to tooth loss.
Dental research shows a genetic component in periodontal disease. The inflammation process that accompanies bacterial infection involves the release of powerful molecules, called prostaglandins, from cells of the immune system. Prostaglandins are produced by cells through the work of several enzymes, each of which derives from one or more genes. One type of prostaglandin, prostaglandin E2 (PGE2), may play a key role in the tissue destruction that occurs in periodontal disease. In healthy individuals, PGE2 levels are very low. Levels of PGE2 increase in gingivitis and rise significantly in periodontitis.
Factors such as smoking, age, level of oral hygiene, level of patient education, and level of professional dental care influence the severity of periodontal disease. Certain metabolic diseases, such as diabetes mellitus, also increase the risk of periodontal disease.
Patients with diabetes are at greater risk for periodontal disease. Diabetes causes blood vessel thickening, which slows down the flow of blood to body tissues, including the gums and dental bones. Blood flow is crucial in providing important nutrients and eliminating harmful wastes from body tissues. As a result of lowered blood flow, the gum and bone tissue supporting the teeth become less healthy and less resistant to infection from bacteria found in dental plaque.
Studies show that patients with poorly controlled diabetes have periodontal disease more often and more severely than those with good control of diabetes. Also, patients with poorly controlled diabetes have more incidence of tooth loss. Studies have also linked an increased risk for gum disease among diabetics who smoke. Smokers with diabetes, age 45 or older, are twenty times more likely to develop severe periodontal disease compared to individuals who do not smoke and do not have diabetes.
Thrush. Thrush (oral candidiasis) is another complication of diabetes. Thrush is an oral infection caused by fungus that grows in the mouth. The fungus that causes thrush thrives on increased levels of blood glucose found in the saliva of individuals with diabetes. Smoking, poor oral hygiene, and denture-wearers are at greater risk for developing this complication.
Dry Mouth. Dry mouth (xerostomia) is another complication of diabetes. Dry mouth is the result of the decrease in production of saliva by salivary glands. As a result, dry mouth can lead to mouth soreness, tooth decay, increased risk of soft tissue infections, and ulcers.
Tooth Decay. Children with diabetes do not show incidence of increased tooth decay. In fact, studies indicate that tooth decay actually occurs less in children with diabetes due to the children's low sugar diets.
Wound Healing. Diabetes causes an increase in the time for wounds to heal following surgeries or injuries. Dentists observe precautions and work closely with the patient's physician when dental invasive treatment is needed.
Offenbacher, S., P.A. Heasman, J.G. Collins. 1993. Modulation of host PGE2 secretion as a determinant of periodontal disease expression. Journal of Periodontology 64:432-434.
Page, R.C. 1995. Critical issues in periodontal research. Journal of Dental Research 74:1118-1128.
Slavkin, H. 1988. Gene regulation in the development of the oral tissues. Journal of Dental Research 1988;67:1142-1149.
Sreebny, L.M., A. Yu, A. Green, A. Valdini. 1992. Xerostomia in diabetes mellitus. Diabetes Care 15(7):900-904.
HOW TO LEARN
www.diabetes.org. This is the American Diabetes Association website, a resource center for diabetes information.
This is the American Academy of
Periodontology website, which offers
information on gum disease and treatment.
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