Spontaneous re-eruption of a permanent maxillary central incisor after 15 years of ankylosis--a case report.

Intrusion injuries are considered among the most severe forms of dental trauma, potentially leading to ankylosis as a late consequence. In 1991, a 7-year-old boy suffered a traumatic intrusion leading to an infraposition of tooth 21 along with its immobility. Based on the clinical findings, including bright-sounding percussion testing, disappearance of the periodontal space and a failed attempt at orthodontic movement, a diagnosis of ankylosis was made. Following prosthetic restoration of the infrapositioned tooth, spontaneous re-eruption occurred 15 years later. With the help of a partial multibracket appliance, the tooth could be adjusted to occlusal level and was then restored to the patient's satisfaction. Radiographically, it was demonstrated that extrusion of the tooth had been accompanied by a significant gain in local alveolar bone volume. While a wait-and-see strategy cannot be recommended as a treatment option following ankylosis, considering that spontaneous re-eruption after several years is an extremely rare finding, elucidating the mechanisms at work in spontaneous re-eruption at a cellular level might create an opportunity for iatrogenic triggering of re-eruption, thus paving the way to new forms of therapy.