Pulp and periodontal healing, root development and root resorption subsequent to transplantation and orthodontic rotation: a long-term study of autotransplanted premolars.

One hundred and eighteen premolars transplanted at a stage with 3/4 to 4/4 root development with a wide open apical foramen were followed with standardized clinical and radiographic techniques for signs of pulpal and periodontal ligament healing and root development. Pulp healing, evaluated first by radiographic presence of pulp canal obliteration, appeared to be an earlier sign of pulp healing than the detection of pulp vitality with an electrometric test. Continued root growth of premolars was seen in some cases. Complete arrest of root development was usually followed by development of the missing root structure at the donor site, indicating a separation of the Hertwig's epithelial root sheath. Orthodontic rotation performed on 11 premolars induced slight surface resorption and a significant shortening of tooth length (mean 1.2 mm), compared with nontreated but transplanted control teeth. However, the extent of the apical root resorption is of minor clinical importance, and is equivalent to what has been found in previous investigations of orthodontic treatment of nontransplanted premolars. Late pulp necrosis occurred in 2 of the 11 treated cases 6 years after transplantation and 5 years after orthodontic rotation. To prevent late pulp necrosis, orthodontic rotation is recommended after periodontal healing and before total pulp canal obliteration has taken place, i.e., 3 to 9 months after transplantation.