An 18 year-old male patient was referred for evaluation of the third and second mandibular molar included. Radiographic examination confirmed the diagnosis. A complementary radiographic examination was performed to ensure accurate treatment planning with CBCT (White Fox, Acteon Medico-Dental Iberica S.A.U, Satelec, Merignac, France), (Fig. 1a) with exposure parameters of 105.0 kVp, 8.0 mA, 7.20 s and a field of view of 6 × 6 mm. The dental models were scanned by an extraoral scanner (EVO, Ceratomic, Protechno, Gerona, Spain) and segmented stereolithography (STL) files were analyzed. (Fig. 1b).
After making an interdisciplinary consultation, the orthodontic treatment was not considered a treatment option for the patient. Therefore, autotransplantation of the right mandibular third molar into the place of the right mandibular second molar was planned as the most appropriate treatment plan. The reason to perform a double extraction was that the patient had already undergone orthodontic treatment when he was 8 years old and afterwards he used a multibracket device when he was 13 years old, which ended in a refusal to undergo a new orthodontic treatment. We knew that the best treatment would have been orthodontics with extraction of the third mandibular molar and second mandibular molar alignment by using miniscrews or mini-implants but the patient refused such treatment and that is why we gave him a second option with an autotransplant of the third molar.
Both digital files obtained by CBCT and extraoral scanner ((Digital Imaging and Medical Communications Files (DICOM) and Standard Triangle Language (STL)) were imported into surgical planning software designed for guided implant surgery (NemoScan, Explora 3D lab, Nemotec S.L., Arroyomolinos, Madrid, Spain) to digitally position the right mandibular third molar. In carrying out autotransplantation in the present case, CBCT images and 3D simulation were particularly useful for surgical simulation.
Similarly to planning using virtual guides of dental implants, the rotation of donor tooth and correct angulation was decided; the accurate positioning of the donor tooth was defined with the aid of STL files of donor tooth and with five surgical pins. The alveoli of the two radicular processes of the right mandibular third molar were created by means of a 3D printed tooth-supported surgical template with five drilling sleeves of ϕ 2.5 mm. The exact 3D position was selected based on its position with respect to the antagonist teeth in the upper arch must be taken into account to ensure functional restoration after surgical intervention (Fig. 1c). This was virtually planned using rotatory surgical instruments. The use of technology planning through CBCT was very useful in this case despite having an alveolus partially created since the axis of extracted tooth is different from the autotransplanted tooth positioned.
Technical STL files of surgical burs and dental implants (Guided Implant Surgery Biohorizons; Biohorizons S. L, Birmingham, USA) were visualized and superimposed onto the osteotomy plan to facilitate final treatment planning. Afterwards, these files were imported into planning software to obtain accurate osteotomies. Once the position and dimension of donor tooth had been virtually designed, a surgical template for guided osteotomy was developed within the software. This template was virtually designed to ensure precise positioning throughout surgical intervention. As a final part of process, the surgical template was exported as STL files and sent to a 3D printer for production (Explora 3D Lab, Nemotec S. L, Arroyomolinos, Madrid, Spain) (Fig. 1d).
Surgery was performed under local anaesthesia using articaine 2% and 1:100000 epinephrine (Artinibsa, Inibsa S.A., Lliça de Vall, Barcelona, Spain). The right mandibular third molar was extracted atraumatically (Fig. 2a) without any bone removal with forceps and it was preserved in autologous plasma rich in growth factors (PRGF) (BTI Biotechnology Institute, Vitoria, Spain) while the extraction of the second molar and the surgery procedure were being carried out (Fig. 2b). The extraoral time was measured and the root surface was not manipulated to enhance PDL fiber attachment. The stability of the 3D printed surgical template was confirmed, before starting the drilling guided procedure (Fig. 2c). The surgical template with five drilling of Ø 2.5 mm was positioned. All drills were 2.5 mm diameter and the first drill was introduced at 15 mm, the second and the third drill at 12 mm and the fourth and fifth drill at 7.5 mm.
A 3D tooth replica was inserted to verify the final preparation of the recipient site (Fig. 2d) but the adaptation was not perfect and, after the position and stability of the dental replica were confirmed, the autotransplanted tooth was inserted and mesially and distally stabilized with sutures across the occlusal plane (Fig. 2e). The total extraoral time was 17 min as a result of guided surgery. Activated PRGF was then applied around the autotransplanted tooth (Fig. 2f). Occlusal contacts were gently removed to keep the transplant from postoperative traumatic occlusal forces. An antibiotic (amoxicillin 750 mg every 8 h), an analgesic (ibuprofen 600 mg) and an antibacterial chlorhexidine gluconate rinse (0.20%) were prescribed for 1 week. The patient was also advised to eat a soft diet for the first few days. The healing process was uneventful and there were no postoperative complications.
Two weeks later, the root canal treatment was performed. A rubber dam (Hygenic® dental dam, Coltene Whaledent Grouppe, Altstätten, Switzerland) was used to achieve total isolation and the working length was determined with an electronic apex locator (Raypex 6®, VDW, Munich, Germany). Preparation of the root canal was performed using Protaper Next® rotary instruments (DentsplySirona Endodontics, Ballaigues, Switzerland). Final preparation of the canals was done with X2 in the mesial canals and X3 in the distal canal. Afterwards, an apical calibration was done to determine the real canal diameter. The smear layer was removed with 5.25% NaOCl and 17% EDTA and activated with Endoactivator® (Dentsply Sirona Endodontics, Ballaigues, Switzerland). After the completion of cleaning and shaping of root canal the treatment was completed using warm vertical condensation technique (Elements®, Sybron Endo, Orange, USA) for obturation of the canals and an epoxy resin cement (AH Plus®, Dentsply DeTrey, Konstanz, Germany) (Fig. 3a). The tooth crown was permanently restored with resin.
The patient underwent clinical and radiographic follow-ups after 1 day (post- operative), 1 week (suture removal), 2 weeks (root canal treatment), 1 month (clinical examination) and 6, 12, 18 and 24 months (clinical/radiographic examinations). The patient was asymptomatic during the post-operative period (Fig. 3b).
After 24 months, clinical and radiographic examinations revealed satisfying results, with no signs and symptoms. The patient has no symptoms and the transplanted tooth is functional with no signs of marginal periodontal pathology. Radiographies and CBCT showed bone regeneration in the site of previous third molar, normal periodontal ligament with no signs of pathology of root resorption (Figs. 4a, b, 5a and b).
