The aim of this study was to analyze and compare the long-term clinical outcomes of mature third molar autotransplantation in surgically created sockets and fresh extraction sockets with regard to survival and functional success rates. A total of 65 third molars with completely formed roots were autotransplanted in 60 patients (average age 33.1 years). Thirty-six of the teeth were autotransplanted into surgically created sockets with or without guided bone regeneration (GBR; delayed autotransplantation), while 29 were autotransplanted into fresh extraction sockets (immediate autotransplantation; control group). All patients underwent annual clinical and radiographic examinations (average follow-up 9.9 years, range 7–13 years). The survival rates for the control, GBR, and no GBR groups were 93.1%, 95.2%, and 80.0%, respectively, with no significant differences among the groups. There were no statistically significant differences among the groups with regard to the frequency of inflammatory root resorption or root ankylosis. Age did not influence the clinical outcomes. These results suggest that the autotransplantation of third molars with completely formed roots is effective in both surgically created and fresh extraction sockets and provides a high long-term success rate if cases are selected and treated appropriately.
The autotransplantation of third molars has become a useful and acceptable treatment option for missing posterior teeth in the human dentition. Successful tooth transplantation provides improved aesthetics, arch forms and dentofacial development, mastication, speech, and arch integrity. The total cost of transplantation is also much lower than that of implant treatment.
The autotransplantation of immature third molars has been performed for several years. However, only a few studies have reported the clinical outcomes of autotransplantation of third molars with completely formed roots. Although it has been reported that survival rates of >95% can be obtained after implant placement, implants cannot be used in all cases. The autotransplantation of teeth with complete root formation is indicated for the replacement of one or more lost teeth as a cost-effective treatment alternative to implants.
Revascularization of the pulp is not expected after the transplantation of mature teeth. The histological analysis conducted by Kristerson and Andreasen revealed that root resorption becomes more prominent as root development progresses. Mejare et al. reported a cumulative survival rate of 81.4% over a 4-year follow-up, while other studies have reported survival rates ranging from 71% to 95% after 1 to 3 years of follow-up. However, it appears that no study has assessed the outcomes of the autotransplantation of mature third molars over a long-term follow-up period.
One of the basic prerequisites for successful autotransplantation is an appropriate recipient site. Recipient site conditions vary according to the timing of tooth loss, and different surgical techniques are used under different conditions. For patients requiring the replacement of teeth that cannot be retained, autotransplantation can be performed immediately after extraction of the tooth in question. In such cases, the recipient site generally has adequate bone and can easily be prepared to allow for good approximation between the transplanted tooth and bone.
For patients with conditions such as congenitally missing teeth or early tooth loss, the recipient site for autotransplantation needs to be created surgically. In such cases, there is marked horizontal bone loss at the recipient site, which provides inadequate support for the transplanted tooth. When donor teeth are placed into recipient sites with an inadequate buccolingual space, protrusion of the roots through a bone dehiscence and resorption of the alveolar ridge may occur.
In a study by Aoyama, a narrow recipient site was observed in all failed cases of mature tooth autotransplantation. Thus, a lack of buccal bone plate and a narrow recipient site are considered risk factors for treatment failure. A splitting osteotomy of the alveolar process has been recommended for such cases. However, the splitting osteotomy technique negatively influences the treatment outcome because of inadequate recipient sites and difficult closure. As an alternative, graft materials can be placed over the exposed root to create space for bone regeneration. For the treatment of bony defects around implants, Simion et al. used polylactic acid/polyglycolic acid membranes stabilized with fixation screws or nails and autogenous bone chips to create space. Bone substitutes and guided bone regeneration (GBR) have also been used extensively for the management of bone volume deficiency. However, very few clinical studies have investigated the application of GBR to facilitate mature third molar autotransplantation in patients with osseous defects at the recipient site.
The aim of this study was to analyze and compare the long-term clinical outcomes of mature third molar autotransplantation in surgically created sockets (with or without GBR) and fresh extraction sockets with regards to survival and functional success rates. The indications for the treatment options and surgical techniques were investigated over a long-term follow-up period.
Materials and methods
This was a prospective study. The study protocol was evaluated and approved by the institutional ethics committee of Peking University School of Stomatology prior to patient selection. All patients who were able to understand the procedure and sign an informed consent form were eligible for inclusion in this trial.
Patients were recruited from those referred to the study institution between 2003 and 2006. All patients with one or two non-retainable teeth, early tooth loss, or a congenitally missing tooth in the premolar or molar region were considered eligible. Patients were recruited according to the inclusion and exclusion criteria detailed in Table 1 .
|Voluntary informed consent|
|Age >18 years|
|1–2 non-retainable teeth, early tooth loss, or a congenitally missing tooth in the premolar or molar region|
|Third molars with completely formed roots and with a suitable shape and dimension for the recipient site after clinical and radiographic evaluation|
|Edentulous opposing dentition with a denture (implant-borne or conventional) or natural teeth|
|Rejection of implant placement|
|General contraindications for transplant surgery|
|History of irradiation in the head and neck region less than 1 year before the study|
|Poor oral hygiene|
|Pregnant or lactating|
|Psychiatric problems or unrealistic expectations|
|Severe bruxism or clenching habits|
|Presence of osseous lesions|
All surgical procedures were performed by a single surgeon using standardized surgical techniques. Patients were categorized into three groups. Patients admitted for eventual autotransplantation after the extraction of a molar tooth served as controls. In the other two test groups, patients received third molar autotransplantation in surgically created sockets either with or without GBR.
Removal of donor teeth
In the control group, the donor teeth were extracted under local anaesthesia (lidocaine 2% with epinephrine 1:100,000). Following incision placement and full-thickness flap reflection for complete exposure of the surgical site, an ostectomy was performed for minimally traumatic removal of the donor tooth. Care was taken to preserve the periodontal ligament attached to the root as much as possible. After the diameter and length of the root(s) had been measured, the donor tooth was placed back into the extraction socket for preservation. The maximum allowable extraoral time before transplantation was 30 min.
Surgical treatment of the recipient site
For patients with non-retainable teeth, autotransplantation was performed immediately after extraction of the tooth in question (control group). Following extraction and removal of the intra-alveolar septa using burs, the recipient site was adjusted using dental implant drills (Thommen Medical AG, Grenchen, Switzerland). No additional surgical procedures were required ( Fig. 1 ).
For patients with early tooth loss or congenitally missing teeth (test group 1), the recipient bed was made slightly larger than the donor site and was created surgically using dental implant drills of an increasing diameter; this was performed under abundant sterile saline irrigation to avoid thermal damage to the bone ( Fig. 2 ). For patients with marked horizontal alveolar bone loss or partial loss of the buccal bone wall at the recipient site (test group 2), GBR was performed after transplantation. Bio-Oss and Bio-Oss Collagen (Geistlich Pharma AB, Wolhusen, Switzerland) and a few autogenous bone chips collected during the ostectomy were used to fill the buccal bone defects, after which a resorbable membrane was placed for coverage (Bio-Gide; Geistlich Pharma).
The donor tooth was placed into the recipient bed as soon as possible; the average duration between removal and transplantation of the donor tooth was 15 min.
Fixation of the autotransplanted tooth
The transplanted donor teeth were stabilized with non-absorbable surgical sutures, which were removed 2–3 weeks after surgery to avoid ankylosis.
The dental surgeon ensured that a 40-μm-thick articulating paper could pass between the teeth without resistance, thus maintaining the transplanted teeth out of occlusion. The configuration of the transplanted teeth was adjusted in accordance with the contralateral teeth.
After surgery, all patients were prescribed antibiotics for 1 week and were instructed to rinse with 0.2% chlorhexidine for 20 s three times a day for 3 weeks. Healing was evaluated after 2 weeks. Patients older than 20 years underwent endodontic treatment. For patients under the age of 20 years, vitality tests were performed with an electrometric pulp tester. At the 3–6-month recall, transplanted teeth were treated endodontically with calcium hydroxide if the teeth reacted negatively to sensitivity tests. During the postoperative observation period, root canal treatment was initiated promptly if any sign of pulp infection was observed.
The average duration of follow-up was 9.9 years (range 7–13 years). The patients were evaluated clinically and radiographically at 1, 3, and 12 months after surgery and annually thereafter.
A single clinician, who was not involved in the treatment of the patients, performed all of the clinical examinations without knowledge of the group allocations. The success of autotransplanted teeth was assessed mainly based on peri-apical healing and periodontal health. These factors included an absence of pathological mobility and absence of a continuous radiolucency around the transplant. Other parameters for assessing the success of transplants included ankylosis, inflammatory root resorption, and inflammation at the recipient site.
Panoramic radiographs were obtained before and after autotransplantation and peri-apical radiographs were obtained after autotransplantation for the assessment of root resorption, the periodontal condition, the lamina dura, and ankylosis.
The survival time was censored when there was a follow-up period but failure of the transplant had not occurred. A multivariate Cox regression model was used to analyze the influence of various factors on the survival rate. IBM SPSS Statistics version 20.0 software (IBM Corp., Armonk, NY, USA) was used for all statistical analyses. Significant differences in clinical and radiographic findings among the groups were determined using the χ 2 test or Fisher’s exact test, as appropriate. A P -value of <0.05 was considered statistically significant.
Follow-up was terminated at 31 August 2015 in this study. The study initially included a total of 72 patients recruited consecutively between 2003 and 2006 for the autotransplantation of third molars with completely formed roots after clinical and radiographic evaluations. Five patients with uneventful healing after surgery moved away to other cities during the first year after surgery and were therefore withdrawn from further check-ups. Seven patients could not be contacted by phone, as they lived in remote locations or had work-related conflicts. The remaining 60 patients were included in this trial.
The survival time was defined as the number of years from transplantation to the time of censoring or to the date on which the transplant was recorded as unsuccessful. Overall, 65 third molars with completely formed roots were autotransplanted in the 60 patients (32 female and 28 male; average age at the time of transplantation 33.1 years, range 19–55 years). Table 2 shows the number and distribution of transplanted teeth in the three groups according to sex, age at transplantation, and the observation time. Tables 3 and 4 show the distribution of the transplanted teeth and recipient sites in the maxilla and mandible.
|Prepared socket||Fresh socket|
|Bone graft||No bone graft|
|Number of transplanted teeth||21||15||29||65|
|Male||6 (7)||8 (8)||14 (14)||28 (29)|
|Female||11 (14)||7 (7)||14 (15)||32 (36)|
|Average age, years (range)||27.7 (20–34)||36.8 (21–49)||33.1 (19–55)||33.1 (19–55)|
|Average observation time, years (range)||9.8 (8–12)||10.1 (8–11)||9.7 (7–13)||9.9 (7–13)|