Evaluating the implant candidate 229

nisms and their products. An allergic reaction is similar, except that the substance provoking the immune reaction is normally harmless to most people.

An individual does not notice his first contact with an allergen. However, after dealing with the first exposure to the allergen, the excess antibodies, or antigens, produced against it circulate in the blood for a time and then become attached to various tissue surfaces. Further exposure to the allergen causes the antibodies to tear away from the tissue surface to recirculate and attack the intruder. Tearing away from the tissue cells causes the release of histamine, which circulates to the invasion site and produces the symptoms characteristic of the particular allergy. Sometimes the affected site may be limited, such as to the mucous membranes of the nose. In other cases, the allergic reaction may be more generalized and affect several areas of the body, such as the skin and gastrointestinal tract.

Some people "outgrow" their allergies, particularly children as they mature. In others, the condition becomes more severe and other allergies may develop. Some rare individuals become so hyper-sensitive that they may go into shock and die. This is particularly true of those patients who become sensitized to drugs.

In evaluating an allergy-prone candidate, the operator must consider all phases of the implant procedure. His patient may be allergic to drugs, metals, or plastics. Roentgenograms can also induce changes in the body's proteins that will trigger allergic reactions, and highly emotional episodes are known to be associated with allergic attacks. If the patient is allergic to metal or some other substances sure to be included in an implant prosthesis, he is definitely not an implant candidate. If the patient has a limited allergy, such as hay fever, and is confident in the operator, his judgment, and skill, he is probably an acceptable candidate. However, the patient who has a history of numerous allergies is unusually hypersensitive and can overreact to implant materials. Naturally a person who is allergic to any drug necessary during an intervention should not be considered unless an acceptable drug substitute can be found.

If an allergic reaction does occur during the implantation procedure or postoperatively, the dentist may administer antihistamines. If nervousness or worry provoked the reactions, they probably will subside as the patient gains confidence in his implant denture. If the symptoms do not subside, the implant should be removed.

Cancer

When a tissue begins to grow abnormally, the resulting mass may be benign or malignant. If the mass or tumor is benign, the growing tissues remain in the area and the mass expands in size. If the tumor is malignant, parts of it extend into other body tissues and some sections may break away to start new growths elsewhere in the body. This is cancer.

Cancers are divided into two types according to the site of origin. If the cancer arises from epithelial tissues it is a carcinoma, a cancer that tends to spread through the lymph system. If the cancer arises from connective tissues it is a sarcoma, which usually spreads through the bloodstream.

Cancer can originate anywhere in the body: skin, lungs, liver, stomach, intestine, bone, or sex organs. Usually its cause is unknown. Although it may be cured if recognized and treated early enough, cancer is the second leading cause of death in the United States today.

The symptoms of cancer are innumerable and depend a great deal upon the site or sites involved. Every citizen, particularly over the age of 40 years, should learn the seven danger signals and report to his doctor if they occur.

When cancer has been or is currently present in a site other than the jaws or the oral cavity, the patient's candidacy for implants depends on several factors. If the cancer has been cured, there is no reason why implants should not be used. If the cancer is currently under treatment, the methods of treatment may contraindicate implants. Radiation therapy, radioactive seeds, and certain drugs may affect the bone, teeth, and blood and make the patient particularly prone to infection.

In some patients cancer is never cured, but the patient may live a fairly normal life for many years with periods of apparent regression of his condition. If such a patient would benefit from implants, either physically or emotionally, they may be inserted with the approval and cooperation of his physician. (See also Malignant Lesions, p. 222, and Bone Neoplasms, p. 235.)

Bone disorders

Bone disorders anywhere in the body can affect the fate of an implant. Although the condition may be apparently localized in a distant part of the body, alveolar bone may be affected as substances are with-drawn from it to compensate for a disorder elsewhere or if the condition tends to spread from bone to bone.