(1)
Department of Pathology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
Abstract
Tooth eruption comprises the movement of teeth through the soft tissues of the jaw and the overlying mucosa into the oral cavity. The involved biological processes are not yet entirely elucidated, but the importance of the dental follicle and its role in initiating eruption by regulating alveolar bone resorption and alveolar bone formation has been firmly established. Teeth may erupt too early, too late, not in the proper position or not at all. In the latter event, one speaks of impaction. This is most often seen in lower third molar teeth.
Tooth eruption comprises the movement of teeth through the soft tissues of the jaw and the overlying mucosa into the oral cavity (Fig. 7.1) [1]. The involved biological processes are not yet entirely elucidated, but the importance of the dental follicle and its role in initiating eruption by regulating alveolar bone resorption and alveolar bone formation has been firmly established [2]. Teeth may erupt too early, too late, not in the proper position or not at all. In the latter event, one speaks of impaction. This is most often seen in lower third molar teeth.
Fig. 7.1
Schematic drawing showing movement of tooth germ through oral epithelium during successive stages of eruption
Ankylosis
Ankylosis represents fusion of either enamel, dentin or root cementum with adjacent alveolar bone (Fig. 7.2a–c). It may occur in impacted as well as in normally erupted teeth. It may be the result of any condition in which the vitality of the normally present intervening periodontal ligament has been jeopardised. Sometimes, ankylosis occurs in combination with external resorption. The role of the epithelial rests of Malassez in preventing ankylosis has already been mentioned before (see Chap. 1).
Fig. 7.2
Continuity between root surface covering cementum and bone of the alveolar socket displayed in low- (a), intermediate- (b) and higher-power (c) view
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