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.