A Prospective Study on Autotransplantation of Mandibular Third Molars With Complete Root Formation

Abstract

Study Design: Autotransplantation, if possible, is a viable option for replacing a missing tooth when a donor tooth is available. The most typical tooth transplant is the transfer of a third molar to a first molar site. No immune reaction results from transplants of this nature. It restores the proprioceptive function and normal periodontal healing; thus, the patient can have a natural chewing feeling and natural biological response. Objective: This study aims to evaluate the prognosis of autotransplanted mandibular third molar and also to evaluate the cost effectiveness of the treatment performed when compared to the other treatment modalities for prosthetic rehabilitation. Methods: A prospective study was done in the Department of Oral & Maxillofacial Surgery, Sardar Patel Post Graduate Institute of Dental & Medical Sciences, Lucknow, UP, India, with over 20 patients to evaluate the prognosis of autotransplanted mandibular third molars with complete root formation after atraumatic extraction of first or second mandibular molar, which were randomly selected irrespective of race, sex, caste, and socio-economic status. Regular clinical and radiographical examinations were performed over a period of 1 year and the patients were assessed for pain, swelling, infection, dry socket, periodontal pocket depth, ankylosis, root resorption, tooth mobility, and level of buccal bone in relation to cementoenamel junction (CEJ). Results: Eighteen out of 20 transplants were successful; only 2 mandibular transplants were extracted because of abnormal horizontal and axial mobility and the reason of failure was attributed to fact that the roots of transplant were short and conical and there was lack of alveolar bone height at the recipient site in one patient, while root resorption was the reason for failure of transplant in the other patient. Conclusions: This study assessed the efficacy of autotransplantation of molars and the viability of the procedure to replace unrestorable molar teeth; it also supports the hypothesis that transplantation of a mandibular third molar for replacement of a lost or seriously damaged molar tooth could be a reasonable alternative.

Introduction

The first documented case reports of autogenous molar transplants appeared in the literature in the 1950s. In 1956, Miller described his technique for molar transplantation. Bauss et al (2004) reported on the autotransplantation of immature third molars into edentulous and atrophied jaw sections. [1] The 2 most common types of tooth transplant performed on human patients are (1) homologus transplants or homografts and (2) autologus transplants or autografts. Homografts are transplants between individuals. In all cases of homografting, there is an immunologic reaction which ultimately destroys the transplanted tissue. In homografted teeth, this reaction manifests itself as insidious root resorption. There are no long-term reports of successfully homografted teeth. Autografts are transplants from one site to another within the same individual. No immune reaction results from transplants of this nature. [2]

In the past, the donor tooth was extracted first, and the extracted donor tooth itself was used to contour the recipient alveolar bone in order to fit the donor tooth. However, this method has 2 problems. First, the extraoral time of the donor tooth can be extended because the extracted donor tooth is used as a template for bone contouring. The second problem is that the periodontal ligament of the donor tooth might be injured unnecessarily during a number of trials for fitting into the bone socket. [3] Lee et al reported a lower extraoral time and improved contact between donor tooth and the recipient bone after performing autotransplantation using a computer prototyping for a similar model to the donor tooth or using silver replicas of the donor tooth. [4]

According to Chamberlin and Georig, the modified criteria of success for transplanted teeth are as follows: (1) the tooth is fixed in its socket without residual inflammation; (2) mastication function is satisfactory and without discomfort; (3) the tooth is not mobile; (4) a pathologic condition is not apparent on the radiograph; (5) the lamina dura appears normal on the radiographs; (6) the tooth shows radiographic evidence of further growth of the root; and (7) the depth of the sulcus, gingival contour, and colors are normal. [5]

The presence of intact and viable periodontal ligament cells on root surface of the donor tooth is the most critical factor that determines the amount of healing of an autotransplanted tooth. Besides the risk for inflammation-induced root resorption, transient or permanent ankylosis may develop in case of damage to the root cement during the surgical procedure. [6] The extended extraoral time of the donor tooth significantly affects the viability of the periodontal ligament cells, which leads to unfavorable root resorption.

Several authors have described the risk factors of autotransplantation of donor teeth with complete root formation. Risk factors indicated in the pre- and peri-operative period were age, molars as donor teeth, probing pocket depth of 4 mm or more, history of root canal treatment, multi-rooted teeth, fixation with sutures, donor teeth with caries, and buccal bone coverage of transplanted teeth. [7]

Material & Method

This prospective study was carried out in the Department of Oral & Maxillofacial Surgery, Sardar Patel Post Graduate Institute of Dental & Medical Sciences, Lucknow, with due permission of the ethical committee. Twenty patients were randomly selected according to inclusion criteria, irrespective of race, sex, caste, and socio-economic status.

Inclusion Criteria

• Patients with ASA grade I and II (American Society of Anesthesiologists), between the age group of 21-66 years having fully developed mandibular third molars were selected.
• The transplant should have a suitable shape and dimension for the recipient site.

Exclusion Criteria

• Divergent root morphology of the transplant tooth than the recipient site.
• Patients having bad periodontal health.
• Medically compromised patients.
• Pregnant women.
• Third molars which require sectioning for their removal.
• Periapical or Periodontal pathology with respect to donor or recipient site.

Method

Informed written consent was obtained from each patient.

• Detailed case history of all cases which requires extraction of first or second molar were recorded. All patients underwent clinical examination, routine blood investigation, and Intaoral Periapical Radiograph (IOPA), OPG if required.
• The transplant was chosen with reference to the best morphological conformity possible. Thus, the third molar of the same quadrant of the jaw was the first choice.
• On the basis of radiographical examination, the best suitable replica of third molar to be autotransplanted was chosen from the collection of suitable acrylic replicas (Figure 1).
• Every surgery was performed after obtaining local anesthesia.
• First/second molar extraction was performed in an atraumatic manner, preserving sufficient buccal and lingual cortical plate heights (Figure 2).
• The recipient site was prepared first with the help of bone-cutting burs, chisel, rongeur, filer (Figure 3), and according to the best morphologically similar and chosen replica. The replica was gently tapped into the socket to ensure that the replica appropriately fit the recipient site (Figure 4).
• Mandibular third molar was extracted atraumatically, taking care to avoid damage to periodontal ligament in order to preserve its vitality which is essential for successful outcome of treatment (Figure 5). Simultaneously, precaution was taken not to injure the root surface, and the molar was transplanted into the prepared site with minimum possible lapse of time and less number of attempts to achieve satisfactory fit (Figure 6).
• The transplant was placed preferably with slight approximate contacts to the adjacent teeth, without interference with the opposing teeth.
• Care was taken to avoid occlusal contact from the opposing tooth.
• The transplanted tooth was appropriately splinted with adjacent teeth, and it was left for minimum of 4 weeks (Figure 7).
• Postoperative instructions and medication (5 to 7 days) were given:
  • Tab. cefixime 200 mg BD 1 tab./Cap. amoxycilline 500 mg 1 cap TDS.
  • Tab. Aceclofenac/Tab. diclofenac 1 tab. TDS.
  • Cap. multivitamin 1 cap OD.
  • Tab. ranitidine 150 mg 1 tab BD/Tab. pantoprazole-domperidone 1 tab. BD.
• Regular post-extraction instructions were given with special instructions to take semisolid/soft diet for 3 to 4 weeks and avoid pressure on the operated site. Sutures were removed after 7 days.
• Regular clinical and radiographical examinations were performed on prescribed time for follow-up.
• Medical/psychosocial support was provided, if needed, to all the patients during the surgery and in the whole course of assessment.

Criteria Parameter

The following data were recorded and evaluated: pain, swelling, infection, dry socket, periodontal pocket depth, ankylosis, root resorption, tooth mobility, level of buccal bone in relation to CEJ at intervals of seventh and fifteenth day; 1, 3, and 6 months; and 1 year.

Data Analysis

The statistical analysis was done using SPSS (Statistical Package for Social Sciences) Version 15.0 statistical analysis software. The values were presented in number and mean ± SD. Wilcoxon matched pairs sign rank test, paired “t”-test was used to analyze the data.

Results

Figure 8 shows radiographs showing preoperative, immediate postoperative, seventh day, 3-month, and 1-year follow-ups IOPA. (Figure 8A–E).

Pain [8]

Pain score was recorded at preoperative and postoperative period up to 1 month. Pain score was categorized as no pain: 0, mild: 1-3; moderate: 46; and severe: 7-10 (

Table 1. Summary of Pain in Preoperative and Postoperative Period.

).

Preoperative and postoperative scores of different days were compared by Wilcoxon’s matched paired sign ranked test. Pain was recorded till 1 month, and it reduced sharply from first day to seventh day, after which it slowly reduced (Figure 9).

Swelling [9] (Extraoral)

Increase in swelling from preoperative period to first day was found significant. Swelling reduced from first day to third day; thereafter, the preoperative level was regained to normal by seventh day (Figure 10).

Postoperative Infection

There was no infection seen during postoperative period in all the patients up to 1 month.

Dry Socket

No dry socket was found in any patients under study.

Transplant Mobility [10]

Preoperatively, all 20 cases showed physiological tooth mobility. Abnormal horizontal mobility more than 1 mm was present in-7 patients by seventh day, 2 patients by 15th day, and in 1 patient by 1 month. Thereafter, no such cases were found. This showed gradual improvement in the stability of tooth from 15th day onwards (Figure 11).

Pocket Depth [10](In Millimeters)

Increased preoperatively from 1.8 mm to 4.55 mm by 1 month. It gradually decreased to the preoperative level after 1 year (Figure 12).

Radiographic Assessment

Root Resorption [11,12]

Only 2 cases of root resorption were found in the first month, after which they were extracted. In the rest 18 cases, no root resorption was found (Figure 13).

Buccal Bone [11,12]

Three patients initially had slight loss of alveolar bone height, the preoperative level were reached by 1 year in 2 patients, third transplant did not achieved its preoperative level and was ultimately extracted by third month, and 17 patients had no bone loss (Figure 14).

Ankylosis [4,12]

Only 1 case after 6 months was found to have ankylosis.

Discussion

Although there are many reasons for autotransplantation of teeth, the most common indication is tooth loss. Teeth can be congenitally missing or lost due to incurable trauma, dental caries, or periodontal diseases. [13] Autogenous tooth transplantation has shown to be an effective method for tooth replacement. The main advantage of using an autogenous tooth over a dental prosthesis or an artificial dental implant is that the substitute is a natural tooth requiring no special care. [6] Tooth transplantation offers several benefits compared with other methods, such as implant. First, most tooth transplantation procedures can be accomplished in a single surgery. Second, once it succeeds, the transplanted tooth restores its proprioceptive function and normal periodontal healing; thus, the patient can have a natural chewing feeling and natural biological response. [4] Furthermore, the transplanted tooth can serve as a bridge abutment or as an orthodontic anchorage. [8] The transplanted tooth can regenerate bone, unlike the dental implant, which often requires bone grafting to fulfill all necessary functional and esthetic demands. [1]

Various literatures reported excellent success rates following tooth transplantation when the appropriate protocol is followed. Lundberg and Isaksson [14] had success in 94% and 84% of cases for open and closed apices, respectively, in 278 autotransplanted teeth over 5 years.

We followed the modified Chamberlin and Goerig’s criteria of success for tooth transplantation; these modified criteria are as follows [7]:

• The tooth should be fixed in its socket without residual inflammation.
• Masticatory function should be satisfactory and without discomfort.
• The tooth should not be mobile.
• Any pathologic condition should not be apparent on the radiograph, and
• The depth of the sulcus, gingival contour, and gingival color should be normal.

According to this modified Chamberlin and Goerig’s criteria of success, our study showed 90% success rate at the end of 6 months. Eighteen out of 20 transplants were successful, and only 2 mandibular transplants were extracted after the follow-up of 3 months because of abnormal horizontal and axial mobility, and the reason of failure was attributed to fact that the roots of transplant were short and conical and there was lack of alveolar bone height at the recipient site in one patient, while root resorption was the reason for failure of transplant in the other patient.

Akkocaoglu and Kasaboglu [15] noticed in some patients having root resorption that pain persisted even after 3 months of autotransplantation, while Czochrowska et al [16] and Myles et al [9] found that patients had mild pain during the surgery which subsided gradually over the next 3-5 days. In our study too, we found similar results which clearly showed a gradual reduction in pain intensity from first to third day, and after that, it further decreased up to the seventh day.

Pollmann [9] found that postoperative swelling after oral surgery is in a “circaseptan” (about 7 days) mode and the healing of a wound does not take place continuously; in fact, the swelling start with a decrease of swelling from second up to the fifth day, when measured by measuring the distance between 2 anatomical landmarks: (1) tragus-pogonion and (2) tragus-subnasale. In our study also, we found similar results; in all the 20 patients, the swelling (extraoral) increased on first postoperative day, then showed gradual decline by the third day, and ultimately reduced to the preoperative level by the seventh day.

In the “early studies,” endodontic treatment was said to be always required after a transplantation of full root length with closed apex. Studies of Waikakul et al [8] on 54 transplants showed that autotransplants did not need any root canal treatment within the first year of follow-up, thus showing that the earlier studies conclusions were inaccurate. Their discovery of unnecessary root canal treatment was also consistent with Reich, [1] who found that a 95% success rate of the molar transplantation did not require any endodontic treatment. They concluded that to determine an appropriate time to begin functioning on the transplanted third molar, 1 needs both clinical and radiographic assessments. The patient should have neither pain nor discomfort during chewing. [17] Similarly, in our study, since the patients did not present with any complications in the postoperative period, there was no need of carrying out any endodontic procedures and the patients were asymptomatic after 1 year follow-up. Regarding radiography, it was shown that in most of the cases, a sufficient amount of bone with and without lamina dura to support functioning of the third molar transplant appeared in the third month after surgery (Figure 9), which was in agreement with our study in 18 patients. Therefore, such a transplant could have a full function within 3 months if there are no other complications. [7]

Bauss et al [10] found that teeth stabilized with a suture splint for a week indicated a very good result with a success rate of 92.9% in contrast to success rate of 73.5% in teeth fixed with a rigid splint for 4 weeks. In our study, we achieved good initial stability with good root to bone contact in 18 (90%) of the cases; only in 2 cases of transplant, because of their short and conical roots, the initial stability was not satisfactory. Also, the transplants were secured 1-2 mm in infraocclusion to prevent trauma from occlusion during periodontal healing.

Czochrowska et al [18] and Aoyama S et al [19] concluded in their studies that in context to periodontal pocket depth, there were no clinically important differences between the transplanted and reference teeth. We found that in our study, probing pocket depth increased from the preoperative level to the first month, and thereafter, it came to normal pre-operative levels by end of third month to 1 year, except in 2 transplants which were extracted by the third month.

Waikakul et al [7] studied follow-up of transplanted third molars within 1 year and demonstrated that complete trabeculation of the alveolar bone was seen in 68% of the teeth within 3 months and in 100% in 6 months. We found in our study that 3 transplants initially showed loss of alveolar bone height but the buccal bone regained its preoperative levels by 1 year in 2 of the patients which was in agreement with the former study, the third transplant did not regain its alveolar bone height and was eventually extracted by third month, and 17 patients had no bone loss.

Pulpal response to electric pulp testing (EPT) indicates the presence of nerve fibers carrying sensory impulses; they do not provide any information about the vascular supply, which is the real determinant of pulp vitality. Waikakul et al [11] have reported in their study of 22 transplants that pulp response to EPT appears only in 5-10% of cases at the end of 6 months, while after 12 months, the response was seen in 95% of cases. In our study, only 2 (10%) transplants showed positive response to EPT at 6-month follow-up.

M. Honda et al [13] have used stereolithographic replica of the donor tooth prepared from CAD/CAM using dental cone-beam computed tomography so that the recipient socket of appropriate size and structure was prepared and the donor tooth was extracted just prior to transplantation. In our study, we made a pool of acrylic replicas of third molars which were used to create the socket of the recipient site. Further in our study, the periodontal ligaments were preserved by the atraumatic extraction of the donor tooth, and the transplants were held with the crown and touching of the root surface was avoided. Also, the donor tooth was luxated but still left in the socket to provide a favorable environment to the transplant.

Ankylosis strongly correlates with damage to the root surface during the operation. [15] We found that ankylosis was seen in 1 case of transplant after 6 months, but the transplant was normal in function and showed no periapical radiolucency, and the gingival condition and pocket depth were normal. It was presumed that the ankylosis took place as a result of root surface injury. The 2 most important tools in the assessment of healing appear to be radiographic examination and evaluation of pulp sensitivity. Electric pulp testing is currently accepted as a method to monitor pulpal response because it is easy to use and provides clinically reliable measurements. In a study of autotransplanted premolars, positive EPT responses were observed in only 2% of cases after 8 weeks. This increased to 90% and 95% after 6 months and 1 year, respectively. These findings suggest that pulpal responses of transplants became normal with time. [6]

Autogenous transplantation technique may one day be used as the model for transplantation of a laboratory-grown autogenous tooth. Autotransplantation may be the groundbreaking work for what is to come next—laboratory-cloned and cryopreserved teeth. A tooth bank for the anticipated loss and replacement of teeth in any one individual may be the future of implant dentistry [1]; its science with state of art will definitely promise happiness and healthy smiles of patients for a long time. [19]

Conclusion

The present study assessed the efficacy of autotransplantation of molars and the viability of the procedure to replace unrestorable molar teeth. Our study supports the hypothesis that transplantation of a mandibular third molar for replacement of a lost or seriously damaged molar tooth could be a reasonable alternative to conventional prosthetic rehabilitation or implant treatment in carefully selected patients. Most important for a good result is a careful surgical approach, so as to avoid damage to the periodontal fibers, for which tooth replicas can be used during preparation of the recipient site.

Our study showed that ideally, a donor tooth should be (1) reasonably strong with good root volume and length, (2) easy for extraction, and (3) periodontally healthy. It is clear from our study that autotransplantation of mandibular third molar is a reliable method, with good prognosis for donor teeth with closed apices.