70 Theories and techniques of oral implantology

the lowers tilt lingually, the bite closes, causing the bicuspids and anterior teeth to shift out of proper occlusion. The lower second bicuspids tilt toward the empty site, creating interdental spaces that invite further food impaction. Then the mandibular anterior teeth tilt lingually so that they occlude on the palatal gingivae. The bite becomes further closed and locked. Eventually the teeth of both arches are shifted or tilted out of proper occlusion, resulting in occlusal trauma that leads to periodontal disease (Fig. 3-26) .

Healing of a tooth socket

After tooth loss, bone tends to fill in the socket and obliterate the site. This process, called remodeling, may take several weeks or months, but after a year no further alterations in the bone's appearance can be expected if healing has proceeded uneventfully.

The first stage in healing occurs as the blood that fills the socket after tooth loss forms a clot. This clot becomes organized and eventually is re-placed by immature, then mature bone. During this maturing, the lamina dura gradually thins and disappears. The bone that spans the socket matures to resemble the adjacent bone, except that now that the tooth is lost, the trabeculae of the new bone are usually more irregularly arranged and fewer in number.

The healing bone tends to start maturing at the base of the socket. The walls of the socket heal toward one another. These apical and lateral healing tendencies gradually make the socket shallower

until it disappears altogether. At the surface of the alveolar process a thin layer of cortical bone forms, and the site has healed.

There are several variations in remodeling that may still be considered normal or nonpathologic. In some cases, a clot does not form and the socket is empty. This condition, called dry socket, is usually painful. Eventually the condition will be alleviated as granulation tissue forms and is replaced by bone as normal as that formed through the maturing of a blood clot into bone.

Another normal, but unusual, variation in the healing of a socket is the early formation of a thin diaphragm of bone over the socket's orifice. This probably results from a rapid extension of the perios-

Fig. 3-27. Thin, weak bone with no cortical plate formation at the alveolar crest. (From Worth, H. M.: Principles and practice of oral radiologic interpretation. Copyright © 1963, Year Book Medical Publishers, Inc. Used by permission.)

Fig. 3-28. A, An abnormal healing pattern: after 16 years the sockets have not filled in with bone. B, Partial remodeling is another example of abnormal healing of a socket. (From Worth, H. M.: Principles and practice of oral radiologic interpretation. Copyright © 1963, Year Book Medical Publishers, Inc. Used by permission.)