Intrusion is defined as apical displacement of the tooth into the alveolar bone. It is accompanied by compression of the periodontal ligament, disruption of the neurovascular supply to the pulp, contusion of the cementum and crushing fracture of the alveolar socket. In severe injuries the tooth may be locked into the bone. Clinical findings reveal a tooth that may appear shortened or even missing. In primary teeth the tooth apex is usually displaced labially toward or through the labial bone plate. In permanent teeth the displacement is into the alveolar bone. There is no tooth mobility or tenderness to touch. Radiographic findings reveal the tooth is displaced apically and the periodontal ligament space is not continuous. Determination of the position of the primary tooth in relationship to the developing permanent may be determined by a lateral radiograph. Alternatively, if the apex is displaced labially, the apical tip can be seen radiographically with the tooth appearing shorter than contralateral. If the apex is displaced palatally towards the developing permanent tooth, the apical tip cannot be seen radiographically and the tooth appears elongated. Treatment consists of:
Primary teeth: Allow the intruded tooth to spontaneously erupt unless radiographs indicate intrusion into the developing tooth. The author’s experience has been to measure the amount of tooth exposed beyond the gingival margin. The tooth is measured four weeks later. If any re-eruption has occurred, another measurement is taken four weeks later. This is repeated until the tooth is fully re-erupted (even with the contralateral tooth). If the tooth exhibits no evidence of re-eruption after a four week period, extraction of the tooth is recommended to avoid ankylosis and possible injury to the developing permanent tooth.
Permanent teeth: In immature teeth with incomplete apex formation and intrusion less than 7mm, the tooth is given the opportunity to passively erupt. If re-eruption is not observed within three weeks or if the intrusion was greater than 7mm, active orthodontic or surgical re-eruption is commenced and endodontic treatment initiated (apexogenisis or apexification). In mature teeth, if the intrusion is 3mm or less, the tooth is given the opportunity to spontaneously re-erupt. Intrusion of 3-7mm requires active orthodontic or surgical re-eruption as soon as possible, and endodontic treatment is initiated within three-to-four weeks post trauma. Intrusion greater than 7mm is treated with surgical repositioning. Surgical repositioning is accomplished by gently repositioning the tooth with fingers or with forceps applied only to the crown, avoiding rotation of the tooth in the socket. The tooth is splinted for two weeks and endodontic therapy initiated within three-to-four weeks post trauma.
Follow up treatment:
Primary teeth: Clinical observation after one week. Clinical and radiographic examination every four weeks until the tooth fully erupts, then six months, one year and annually until the successor erupts.
Permanent teeth: Splint removal and clinical examination after two weeks. Clinical and radiographic examination after four weeks, six-to-eight weeks, six months, one year and yearly for five years.