Material and methods

The sample included 23 consecutively autotransplanted second premolars with developing roots. The mean stage of root development was 4 (two thirds of the final root length), ranging from 2 (a quarter of the final root length) to 6 (full root length, wide open apex). The mean observation time after surgery was 35 months (range, 6-78 months). The teeth were transplanted in 19 patients (10 girls, 9 boys); the mean age at the surgery was 12 years 8 months (range, 9 years 10 months-17 years). Seventeen maxillary and 6 mandibular second premolars served as donor teeth to replace 2 maxillary and 13 congenitally missing mandibular second premolars and 4 maxillary central incisors lost from trauma. One maxillary and 3 mandibular ectopic second premolars were transplanted to a correct position (transalveolar transplantation) because orthodontic traction was considered impossible ( Fig 3 ). All premolars were transplanted by the same oral surgeon (P.P.) and had 2 months of clinical follow-up of tooth transplantation at the Department of the Oral Surgery and Oral Medicine at the University of Oslo in 2000 before this study.

A, Radiograph of the ectopic mandibular second premolar embedded below the medial root of the first molar in a 15-year-old girl; B, 1 week after surgical repositioning of the mandibular right second premolar (transalveolar transplantation), the former crypt of the premolar appears as a bony defect; the transplant was secured with a steel ligature bonded to its crown tip and the neighboring teeth for 10 days; C, 2 years after transplantation, the bony defect has healed; D, 27 months after transplantation, there was no hard-tissue pathology or pulp obliteration, and the root of the transplant ( left ) was slightly shorter root than the control premolar ( right ); E, normal clinical appearance of the transplant.

Twelve second premolars, contralateral to the donor sites, served as the controls for intraindividual comparisons in the subsample having control teeth (12 pairs). No control premolars were available for 11 transplants (subsample without available controls) because 4 patients (8 transplants) had agenesis of both mandibular second premolars; consequently, both maxillary second premolars were transplanted ( Fig 1 , A-E ), and 3 patients (3 transplants) had agenesis or previous extraction of the contralateral premolar ( Fig 2 , B and F ).

All transplantations were performed under local anesthesia (articaine 4% with epinephrine 1:100,000). The first stage of the surgery aimed to gain access to a developing donor tooth because all teeth, except for 2 premolars in 1 patient, had not erupted ( Figs 1 , A, 2 , B, and 3 , A ). When a deciduous molar was present at the donor or recipient site, it was extracted at the beginning of the surgery. The first incision was made along the gingival margin followed by a vertical release of a flap on the buccal side at the donor site. The labial cortical plate covering the donor tooth was carefully demarcated with a bur under copious saline-solution irrigation. A thin layer of trabecular bone adjacent to the graft was gently removed with an excavator to prevent any damage to the root surface. The donor tooth was assessed for whether it could be removed atraumatically with intact dental follicle, cementum, and Hertwig’s epithelial root sheath. If this assessment was positive, then the recipient site (second stage of the surgery) was prepared using a conical bur under copious saline-solution irrigation until the size of the new socket could easily accommodate the donor tooth with surplus space of 1 mm around the root. When a recipient site was prepared in the anterior maxilla, the new socket was sometimes partially open on the labial side, as the result of bone loss after trauma and surgical dehiscence created by the preparation. If a further adjustment in size or shape of the recipient bed was necessary, the donor tooth was kept in the saline solution to protect it from drying for a maximum of 15 minutes.

In the third stage of the surgery, the donor tooth was transferred and positioned in the recipient site, ensuring no occlusal contacts during the initial healing. The donor was stabilized with sutures that crossed over the premolar’s cusps. When the transplantation was performed in the anterior maxilla, the bone dehiscences on the labial aspect were filled with remnants of the donor’s follicle.

The operating time was approximately 60 to 90 minutes. In all patients, healing was uneventful, with no signs of edema or inflammation.

The patients were recalled 2 weeks after the surgery for suture removal, at 1 month and every 3 months during the first year, and then once a year. Intraoral radiographs, mobility tests, and electric pulp testing were performed to detect possible complications (resorption, arrested root development, or pulp necrosis). At the final clinical examination, all transplanted and control premolars had erupted and were in contact with the opposing teeth. All transplants and controls had completed their root formations.

Four transplanted premolars were subsequently bonded with orthodontic brackets. Three of the 4 premolars transplanted to the maxillary anterior segment were reshaped with composite 12 to 24 months after the surgery.

The percentage of transplanted premolars present at the examination relative to the number of all transplanted teeth was called the survival rate. The success rate was calculated as the percentage of transplanted premolars fulfilling established success criteria in relation to the number of transplanted teeth. The criteria included no progressive root resorption, normal hard and soft periodontal tissues, and a crown-to-root ratio less than 1.

The clinical examination was performed by a trained and calibrated examiner (P.P.) using an electronic probe system (Florida Probe, Gainesville, Fla). The examination included plaque accumulation (0, not present; 1, present; recordings at 3 locations on the buccal side and 1 on the lingual side of a tooth), gingival recession height, and pocket depths. For each examined tooth, recession height and pocket depths were recorded at 6 locations (medial, central, and distal) on the lingual and buccal sides. For 2 transplanted and 2 control premolars, no pocket depth measurements were available. Tooth mobility was tested using the Mühlemann index. The percussion test, radiographs, and a distinct infraocclusion were used to detect signs of ankylosis (replacement resorption). Electric pulp testing was performed to determine pulp sensitivity when the electric pulp testing probe was brought into the contact with the buccal surfaces of the tooth.

Standardized, intraoral film radiographs (long cone-beam parallel technique) were used to examine the hard tissues, the outline of the alveolar socket (presence of lamina dura), and the pulp obliteration ( Figs 1 , E , and 3 , D ). The radiographs were taken using a positioner (x-ray holders), which was placed on a film, 30.5 × 40.5 mm, parallel to the long axis of the tooth and perpendicular to the x-ray central cone. The intraoral radiographs were assessed by 2 examiners (P.P. and E.M.C.), and the results were registered when both examiners agreed. Crown and root lengths were measured using digital calipers for calculation of the crown-to-root ratios. The measurements were repeated twice 8 weeks later, and the measurement errors were estimated using Dahlberg’s formula and Houston’s coefficients of reliability ( Table I ).

All patients were asked to fill in a questionnaire that included 7 questions ( Fig 4 ). The questionnaire addressed how the surgical procedure was perceived (5 questions) and asked the patient’s opinion about the current status of the transplanted tooth (2 questions). The answers were recorded using a 57-mm visual analog scale.

Questionnaire used to evaluate the patients’ opinions about the surgery and the outcome with means ( boxes ) and ranges ( arrows ) of their responses in red .