Genetic Considerations of Diseases and Disorders that Affect the Oral Cavity
Part II. Oral Cancer and Developmental Disorders
OF THE ORAL CAVITY
FOR DEVELOPING ORAL CANCER
Genetic Factors. Genetic factors involved in the development of cancer include:
Tobacco and Alcohol. Use of tobacco and alcohol are the major risk factors for developing oral cancer. Tobacco and alcohol contains substances that are carcinogenic or promote cancer. Cigarettes smoke and substances in smokeless tobacco have received considerable attention as carcinogens that promote oral cancer. Studies also indicate that smoking in combination with consumption of alcohol produces an even greater risk for oral cancer than use of either substance alone.
Radiation. Radiation of high dosage and prolonged duration can produce cancer. There is no evidence that routine dental X-rays are carcinogenic, especially with today's high speed, low dosage machines.
Traumatic irritation. Prolonged irritation from broken teeth, rough dental restorations, and ill-fitting dentures are considered a possible causes for oral cancer.
Viruses. Some viruses can cause cancer in human cells. Studies have indicated a link to oral cancer with infections from herpes simplex type- I virus, Epstein-Barr virus, and human papillomavirus.
LESIONS OF THE MOUTH
Leukoplakia. Leukoplakia is a term that describes a 'white patch' on the surface of oral tissues. Leukoplakias have been associated with pre-cancerous tissues. In general, leukoplakias are suspected as pre- or early cancer if the white area cannot be scraped off the surface tissue and cannot be attributed to another disease.
Erythroplakia. Erythroplakia occurs in the oral cavity as a distinct and well-defined patch with a bright red and velvety surface. Erythroplakias are relatively rare lesions of the oral cavity. Erythroplakias are almost always pre-cancerous.
OF SELECTED ORAL CANCERS
Cell Carcinoma. Squamous
cell carcinoma is the most frequently
occurring malignant cancer of the
oral region. This type of cancer
involves cell growth changes of
the surface tissue of the oral region,
the epithelium. Nearly 90% of all
oral cancers are squamous cell carcinomas.
The most frequent location of this
cancer is on the lips, the tongue,
and the floor of the mouth. A chronic
(long-term) mouth ulcer that does
not heal, a lesion attached to deeper
tissues, and a red-velvety lesion
are all suspect squamous cell carcinomas.
If left untreated, squamous cell
carcinomas undergo metastasis and
involve vital organs of the body.
Many times death is the result of
complications to the heart and lungs.
Treatment of most cancers of the head and neck involve a combination of surgery, radiation and chemotherapy.
DISORDERS OF THE HEAD
OF SELECTED DEVELOPMENTAL DEFECTS
Craniosynostoses. Craniosynostoses is a genetic disorder that causes early fusion of the bones surrounding and protecting the brain (bones of the skull). As a result, dangerous amounts of pressure are created against an enlarging brain within a braincase that is not growing. Several hereditary syndromes include mental retardation due to craniosynostoses as a characteristic feature.
Hereditary Anodontia. Conditions of the complete absence of teeth (anodontia) have been correlated to specific genes. The complete absence of teeth alters bone development within the upper and lower jaws of the mouth.
Amelogenesis Imperfecta and Dentinogenesis Imperfecta. Amelogenesis imperfecta is a genetic disorder that results in defective enamel formation of teeth. Enamel is the hard surface covering the crowns of teeth. Amelogenesis imperfecta either causes problems in enamel hardening (mineralization) of normal amounts of enamel or causes a smaller amount of normal enamel to be produced. Dentinogenesis imperfecta is a genetic disorder that results in defective dentin formation within teeth. Dentin is a mineralized material forming the bulk of each tooth. Defective dentin causes the normal enamel layer that covers the tooth to flake off. In both diseases, the teeth are weak and very sensitive to temperature and pressures. Amelogenesis imperfecta and dentinogenesis imperfecta are linked to defects in structural genes that code for proteins necessary for the development of enamel and dentin.
Osteogenesis Imperfecta. Osteogenesis imperfecta is an inherited disease caused by mutations of genes that produce collagen. Collagen is an important substance within connective tissues of the body such as bone. Osteogenesis imperfecta causes 'brittle bone' diseases that affect all bones of the body. A complication of osteogenesis imperfecta that involves tissues of the mouth in addition to the more generalized effect of fragile bones is a painful dentinogenesis imperfecta-like change in the teeth.
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HOW TO LEARN
www.aaoms.org This is the American Association of Oral and Maxillofacial Surgeon website, which contains information about oral and maxillofacial surgery including oral cancer.
www.tonguecancer.com This site provides diagnosis and treatment for cancers of the head and neck.
www.clapa.cwc.net This is the Cleft Lip and Palate Association website, which provides information and support to anyone with or affected by cleft lip and clept palate
www.cleftline.org This is the American Cleft Palate-Craniofacial Association website. This national organization provides lay and professional services for cleft lip, cleft palate, and other craniofacial defects.
ABOUT THE AUTHOR