Evaluating the implant candidate 231

and that the disease does not recur. It is important to note here that a dentist can cause osteomyelitis with unsterile instruments and faulty procedures. Therefore all cutting tools must be sharp and sterile. Water sprays and sharp instruments must always be used when entering the bone to avoid burning it.

Tuberculosis. Tuberculosis of bones and joints is characterized by a chronic destructive lesion caused by infection with Mycobacterium tuberculosis, a microorganism circulated in the blood from a primary focus elsewhere in the body, usually the lungs. The disease usually begins in the metaphysis of one of the bones forming a joint, or it may start in the synovial membrane. A lesion in the metaphysis is characterized by destruction without bony repair. Bone involvement starts late when the disease occurs in the synovial membrane, since the progress of the disease is slow. A tubercular abscess occurs in most of these cases and may follow the fascial planes, appearing near the surface some distance away from the joint.

The symptoms of tuberculosis include joint swelling, which appears rather slowly, and a small amount of heat and tenderness. The accompanying pain is far less aggravating than would be expected, considering the extent of the disease. Because of the lack of severe symptoms, diagnosis is often delayed. Some of the early signs are a limitation of joint motion caused by muscle spasm. A stiffness and

Fig. 6-38. Tuberculosis of the jaws presents a complex picture in this boy. In addition to slight osteitis in the region of the second molar and inferior margin of the jaw, there is a large region of subperiosteal bone of unequal density. (From Worth, H. M.: Principles and practice of oral radio-graphic interpretation. Copyright 1963 by Year Book Medical Publishers, Inc. Used by permission.)

limping can occur in the lower extremities, and rigidity of the back and changes in posture appear early in spinal tuberculosis. The bone is usually osteoporotic on x-ray evaluation. In primary bone cases, lysis and destruction without production of new bone occur.

The focus of infection may usually be destroyed with antituberculosis drugs. Drug therapy should be continued for at least 12 months after apparent recovery. As with any other type of bone disease caused by microorganisms, an implant intervention should be postponed until well after the apparent recovery period to avoid promoting a recurrence of an apparently dormant disease.

Tuberculosis of the mouth, which was formerly considered to be rare, is apparently not as unusual as previously believed. Because the radiographic appearance of the lesions resembles that of other conclitions, it is difficult to correctly diagnose the condition. even when tubercular lesions are present elsewhere in the body.

Tubercular lesions of the alveolar bone and jaws may be localized or diffuse and of any size. They are also frequently accompanied by pyogenic lesions, which are difficult to distinguish from soft tissue lesions caused by the tuberculosis microorganism. One method of extending the infection into bone may indeed be from a tuberculous gingival lesion through a carious tooth into the bone.

Tubercular infection alone rarely causes the proliferation of new bone, although spina ventosa and some other types may produce new bone formation. New bone does tend to proliferate under the periosteutn when tuberculosis is accompanied by a pyogenic infection (Fig. 6-38). Thus when both bone destruction and new bone formation are seen in x-ray studies, a mixed infection should be suspected. Tissue should be removed for pathologic and bacteriologic study to determine the true causes of the lesions, since treating one cause will not cure the other.

As with any other bone infection, implantation should be contraindicated or delayed until the condition is alleviated. Even if the condition is controlled or cured, resultant abnormalities may make implantation difficult, if not impossible.

Degenerative arthritis. Degenerative arthritis appears to be a natural consequence of aging, usually becoming noticeable after the age of 40. Soon after maturity in most people, the gliding surface of the cartilage begins to wear away, a process that may take a few to many years, depending on the indi-