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The lamina dura is part of all human and animal teeth. It comprises only part of the tooth, covering the roots below the surface of the gum. This thin layer of bone connects the roots of each tooth to the periodontal ligament inside each tooth socket.
The only way to see this part of the tooth is through an X-ray. On the image, it appears as a very pale, white outline around the root of each tooth. The thin, dark gap outside the lamina dura is the periodontal ligament, and the gray matter inside the tooth is the cancellous bone. The lamina dura separates them and keeps them both from becoming infected.
Although it is important, this thin layer is a relatively perfunctory part of the tooth. When children lose teeth or adults have them pulled, this part of the tooth dissolves back into the gums. If it begins to dissolve away from the roots of an existing tooth, however, it could indicate periodontitis.
Patients who have periodontitis will experience inflammation of the gums because of infection and dissolving lamina dura. When lamina dura plates dissolve from existing teeth, they expose the soft cancellous bone underneath. The cancellous bone produces red blood cells for the teeth, similar to bone marrow in the rest of the skeleton.
Periodontitis beings with slightly swollen gums indicating mild gingivitis and no lamina dura loss. As the disease progresses, the lamina dura disappears and lesions form under the surfaces of the gum, against the roots of the infected tooth. Periodontitis can spread throughout the mouth very quickly and progresses steadily if left untreated. Untreated cases might result in soft, severely decayed teeth or even tooth loss.
Lamina dura does not come back if it dissolves. Early treatment and exceptional dental hygiene can keep these essential plates intact, however. People who have gum inflammation should consult a dentist about treatment as soon as possible.