68 Theories and techniques of oral implantology

Bundle bone

Periodontal ligament

Bundle bone

Lamellated
haversian
bone

A   B

Fig. 3-24. The periodontal ligament of a functioning tooth is thicker than that of a non-functioning tooth. A, The periodontal ligament of a functioning tooth contains well-oriented fibers, the cementum of the tooth is thin, and there is bundle bone with Sharpey's fibers. B, The periodontal ligament of a nonfunctioning tooth has lost is ligament-like properties; there are no true fiber bundles. The cementum has thickened and the alveolar bone has lamellated with no Sharpey's fibers. (From Sicher, Fl., editor: Orban's oral histology and embryology, ed. 6, St. Louis, 1966, The C. V. Mosby Co.)

bined with shifts in the teeth bordering the site formerly occupied by the functional opponent, con-tribute to malocclusion and its consequent problems.

Results of tooth loss

Because all the teeth act together to ensure harmonious occlusion, occlusal imbalance develops when one is lost. The tooth in the opposing jaw, having lost its functional antagonist, usually tends to drift mesially and to tilt or extrude beyond its occlusal plane. Although the drifting is not a pathologic phenomenon at this stage, the resulting occlusal disharmony can produce periodontal disease, shifting of the other teeth, malocclusion, periodontal injury, and caries.

An example of what happens when one tooth, the first permanent mandibular molar, is lost illus

trates the dangers of uncompensated tooth loss. The lower second molar tilts lingually and mesially to-ward the empty site. In the space created between it and the third molar, food tends to be impacted. Also, the shift now puts the distal half of these teeth into traumatic occlusion, provoking periodontal in-jury. The functional opponent of the lost tooth in the upper jaw, the first maxillary molar, begins to extrude and may continue to do so until its palatal root is denuded. This, combined with the drifting in the lower jaw, creates even further occlusal disharmony.

The problem is compounded as both upper and lower molars tilt even further and occlusal forces are no longer transmitted along the long axes of these teeth.

As the upper molars tend to shift buccally and