Tooth Autotransplantation: An Overview and Case Study

Tooth Autotransplantation: An Overview and Case Study

Samuel K. Schmidt, D.D.S.,* and David G. Cleverly, D.D.S.**:
 
 
A B S T R A C T
It is not uncommon for children or young adults to have congenitally missing teeth or early loss of teeth from trauma or caries. The restorative options are typically bridges, implants, and removable appliances. Often overlooked and misunderstood, another treatment option exists in autotransplantation, where a tooth is moved from one site to another in the same individual. Autotransplantation is well studied and has predictable results comparable to implants, with reported success rates often greater than 90%. This article will provide an overview of  autotransplantation, its indications, advantages, complications, and treatment considerations, along with a case of a third molar autotransplant that will serve to highlight these points. 



Overview
When one hears the word “transplant”, many think of organs such as kidney, lung, liver, or heart. Often those organs save lives, so that is appropriate. Most people, however, are unaware  that a procedure to transplant teeth exists as well. Tooth autotransplantation provides a viable and predictable treatment option that has been studied for many decades. Over the last 20  years, implants have become such a popular treatment to replace missing teeth that autotransplantation has been overlooked by many dentists. Yet the goal of any tooth autotransplant is  the same as that of an implant: to replace a missing or non-restorable tooth, and to provide increased function Tooth Autotransplantation: An Overview and Case Study and, potentially,  esthetics. Thus it is a procedure that both the public and the profession should think of more readily when treatment planning. 
 
Autotransplantation of teeth is surprisingly well studied, and success rates are routinely found to be 90% or higher. In a recent study, Sugai et al followed 114 transplants and found a one- year success rate of 96%, with 84% at five years.1 Other studies have shown between 79 and 95% success rates, with follow-up times as long as 41 years.2,3,4 Another recent study, by Bae et al, showed that high success rates (84%) can even be achieved with closed apex teeth and root canal treatment.5 It is important to recognize that transplanting fully formed teeth  requires root canal therapy, which lowers success rates as well as negating some of the advantages of autotransplantation. Transplantation of a tooth with incompletely formed roots allows  for the advantage of maintaining vitality. According to the Moorrees classification system for stages of root development,6 the key stages for autotransplantation are stages 3 and 4 – i.e.,  one-half to threequarter formed (Figure 1). However, root development is only one of the significant factors that determine success. Patient selection is important since age, health status,  dental status (caries risk), and oral hygiene can influence success. Surgical technique is also vital in regard to manipulation of donor tooth, extraoral time, and atraumatic extraction,7  particularly if the donor tooth is impacted. 
 
The most common indication for an autotransplant is when a molar, classically a first molar, is lost at an early age. Often the patient will have a third molar that could be used well as a donor  tooth due to relative size and proper root development. Other indications include congenitally missing teeth, trauma, or ectopically positioned teeth. Additionally, literature reports have shown  the successful use of premolars, frequently extracted during orthodontic treatment, to replace anterior teeth due to aplasia or trauma.8 
 
While an autotransplant is not always an indicated  treatment, when it is, there are often more traditional and well known alternative treatments that are given as treatment options for patients. These alternatives are usually a bridge or an implant. Implants are often the best treatment available, and in the case of edentulous patients, older adults, or patients with very high  caries risk, implants are clearly the better, and sometimes the only, choice. However, in the relatively few patients where an autotransplant is an indicated and possible treatment, autotransplantation possesses many distinct advantages over implants in terms of function, cost, time, esthetics, and ease with which complications can be managed (Table 1).9 It is also a  surgical procedure that oftentimes can be done in a simple, efficient manner. 



Sequence/Procedure
The procedure of a successful tooth transplant must start with a thorough clinical and radiographic examination. Having as accurate an idea as possible of the size of the donor tooth and the  recipient site makes the procedure go more smoothly and successfully. Once planned properly, the first step in the procedure is removal of the diseased tooth, if present, and surgical  manipulation of the recipient site as much as possible. In cases where no tooth is present, often due to a congenitally missing tooth, surgical creation of the socket can be performed, with  success rates comparable to having a socket present from extraction.10 There have been studies on the effectiveness of using a CAD/CAM-generated replica tooth to determine the recipient  site dimension based on radiographic data, and have shown it can shorten the procedure time as well as prevent injury to the periodontal membrane of the donor tooth.11 The goal should be to minimize handling and extraoral time of the donor tooth during the procedure. 
 
Once the recipient site is prepared adequately to the estimated size needed for the donor tooth, atraumatic extraction of the donor tooth is performed. Minimizing mechanical trauma is vitally important to the ultimate success of the treatment, as the periodontal ligament (PDL) is crucial.12 The donor tooth must then be “tried in” to the recipient site to make sure it will fit properly  and to determine what type of splinting will be necessary. The PDL is still very important in this step, and it is advantageous to try-in the donor tooth as few times as possible. The ideal  scenario would be the donor tooth fitting perfectly into the recipient site the first time, and pre-operative planning can aid greatly in the attempt to achieve such a scenario. 
 
The transplanted tooth should always be placed in infraocclusion and then splinted in place. There are two primary ways to splint a transplanted tooth, either rigid or flexible fixation. Rigid  fixation typically is done for three to four weeks with stainless steel wire and composite, similar to what is done for an avulsed tooth. It has been shown that this type of fixation can  negatively influence root development, and has an increased chance for pulpal necrosis and ankylosis.13Yet, this type of fixation is required if initial stability is not adequately achieved with  suture splinting alone, usually if 2 mm or more of mobility are present after transplant. Suture fixation is the preferred and best option, typically performed by placing a 2-0 silk suture that  crosses the occlusal surface of the transplant through the gingiva labio-lingually for one to two weeks. Postoperative instructions are similar to a typical surgical extraction or implant  procedure. It is common to provide prescriptions for one week of antibiotics and chlorhexidine rinse. The advantage of placing a silk suture is that the practitioner will get to see the patient  on recall in one to two weeks and can get an initial evaluation. If the transplant has a closed apex, then root canal therapy can be initiated approximately two weeks after transplantation. 
 
As transplanted teeth are evaluated at subsequent follow-up appointments, a thorough clinical examination should be performed looking for percussion sound, mobility, function, occlusion, and  gingival health. It is typical to have abnormal pulp testing for up to six months even with normal healing. Additionally, radiographs are an important tool to evaluate PDL and lamina dura, root  formation, and alveolar bone level. Potential complications to be aware of include ankylosis, periodontal disease, root resorption, and pulp canal obliteration.14 That said, most common  sequelae from autotransplants are deviations from ideal tooth position, with as many as 30% without occlusal contacts and up to 15% without interproximal contacts.15 Orthodontic  treatment can correct many positional deficiencies with minimal risk to the periodontal or pulpal health of the transplanted tooth, though it should be performed between three to nine months following transplantation.16 Depending upon the preferences of the patient and clinical significance found by the dentist, minor tooth position discrepancies will often not require additional  treatment. 


Case Study
While a chief resident in the oral and maxillofacial surgery program at Gundersen Lutheran, Dr. David Cleverly treated a 17-year-old female patient, T.O., who presented as a selfreferral. T.O.  had a previously treated root canal on #19 with a PFM crown that had a large periapical radiolucency around both the mesial and distal roots into the furcation space (Figure 2). The tooth  was deemed non-restorable. She also presented with vertically impacted #1 and #16, and mesio-angularly impacted #17 and #32 that were treatment planned for extractions. 
 
Treatment options presented to the patient to replace the soon-to-be-missing #19 included no treatment, RPD, FPD, and implant. No treatment would include the loss of chewing function of  a first molar and potential future restorative problems due to drifting or supraeruption. A removable partial denture would be a step up in providing function and space maintenance, but represents a considerable amount of material to replace a single tooth. A three-unit bridge for #18-x-20 was another alternative option, but one that comes with the undesirable effect of  removing tooth structure from #18, which had only an occlusal amalgam and an unrestored #20. The treatment option would offer with a good long-term prognosis is an implant. Dr. Cleverly added autotransplantion, discussing the aforementioned risks as well as benefits over an implant.
 
Pre-operative measurements and assessments were performed with a panoramic radiograph. Tooth #19 was extracted, and the socket was thoroughly curetted and irrigated with sterile  saline. Freeze-dried bone allograft was placed in the large bony defect. Tooth #17 was atraumatically extracted, and the donor tooth was transplanted into the #19 site. The donor tooth fit  well on the first attempt without any need for further modification of the recipient socket or tooth. Initial stability was excellent, and likely did not require splinting, but a suture splint was placed to minimize risk of dislocation or aspiration of the transplanted tooth (Figure 3). Postoperative instructions and prescriptions were as follow: Chlorhexidine mouth rinse 0.12% twice a  day for seven days; Clindamycin 300 mg every six hours for seven days; Hydrocodone 5mg/ Acetaminophen 500mg every four to six hours for pain as needed.  
 
The patient was seen for an initial post-op appointment at one week, at which time the suture splint was removed and healing was determined to be progressing normally. The patient was  seen again at 10 weeks, and again at four months, when a more thorough clinical and radiographic examination was performed. Probing depths all around the transplant were less than 3 mm, with normal gingival contours and adaptation to the transplant. Tooth #19 tested normal to cold, percussion, and palpation, and occlusion was present and functional. There was a slightly  open mesial contact, and #18 and #19 had Class I mobility. Esthetically, the tooth would appear a natural part of the dentition (Figures 4 and 5), a result even the most talented clinician  would have difficulty reproducing with an implant.  Radiographically, the alveolar bone level is normal, as is the PDL. The pulp chamber is normal, and the apices are open and roots still forming  (Figure 6). 
 
The patient was seen again for a one-year recall with another clinical and radiographic examination, highlighting the importance of good surveillance. The clinical examination showed no  significant findings, there was no longer any mobility, and the open mesial contact is less than at the fourmonth appointment. A periapical radiograph showed similar findings (Figure 7), and it  would be expected that the roots may continue to form another few millimeters, but quite unlikely to approach the length of #18, as root growth is impaired or arrested up to 79% of the  time.17,18 


Discussion
Dr. Cleverly’s case provides an excellent example of how ideal indications for an autotransplant can lead to a very successful treatment outcome. The loss of a first molar at an early age is the most common scenario that would present, and the patient in this case still had a donor third molar with ideal root form. Though an implant would have been a completely reasonable  treatment plan for replacement of #19, it would likely have cost substantially more and taken approximately six months longer before a functional tooth was present. As would be the case for  many young adults, having the option of a tooth transplant was an excellent treatment option both for the dollar savings and for being able to keep a natural tooth.  
 
In this case there have been no major complications to date, highlighting how successful an option transplantation is when properly indicated. The open mesial contact is a by-product of the  donor tooth being smaller than the recipient site, which is typical due to the large mesial-distal dimension of the first molar. Mesial drift has already begun to close the space, and would be expected to continue. Thus the patient has no plans to undergo orthodontic treatment. Proper oral hygiene instructions and encouragement will be important to keep the autotransplant site  clean and to prevent future problems. Overall, at this point the case would be deemed a success, but further follow-up will be important in the next one to two years. 
 
Conclusion
Autotransplantation has been studied extensively for many years and may become a more common procedure as it is better understood by clinicians. Certainly more research to understand  failures and how surgeon experience or extraoral manipulation contribute to failures will be important. However, it is the ongoing research in cryopreservation that makes the future possibilities  so exciting. Studies have shown that PDL cells can survive cryopreservation,19 and while currently cryopreserved teeth require root canal therapy due to inadequate pulpal tissue  preservation,20 there has been initial research suggesting pulpal stem cells are receptive to the treatment.21 Further research could provide methods to make tooth banks a reality, and  provide patients options to replace missing teeth with their own natural teeth instead of implants. Tooth autotransplantation is a procedure that any general dentist could perform if he or she is comfortable with and skilled at dentoalveolar surgery. If extracting impacted teeth, placing implants, and handling surgical complications are fairly routine, autotransplantation is simply a  different procedure using the same skill set. Yet, even general dental practitioners who would not perform the procedure should be knowledgeable about the indications, treatment sequence,  and follow-up so that it can be offered as a treatment option when indicated. Patients will probably be thrilled to hear they could save time and money!  
 


References
1. Sugai T et al. Clinical study on prognostic factors for autotransplantation of teeth with complete root formation. Int J Oral & Maxillo Surg 2010;39(12):1,193-203.
2. Reich PP. Autogenous transplantation of maxillary and mandibular molars. J Oral & Maxillo Surg 2008;66(11):2,314-7.
3. Czochrowska EM et al. Outcome of tooth transplantation: Survival and success rates 17-41 Years posttreatment. Am J Orthod & Dentofacial Orthopedics 2002;121(2):110-9.
4. Lundberg T, S Isaksson. A clinical follow-up study of 278 autotransplanted teeth. Brit J Oral & Maxillo Surg 1996;34(2):181-5.
5. Bae JH et al. Autotransplantation of teeth with complete root formation: A case series. J Endo 2010;36(8):1,422-6.
6. Moorrees CFA, Fanning EA, Hunt EE. Age variation of formation stages for ten permanent teeth. J Dent Res 1963;42:1,490–1,502. 
7. Tsukiboshi M. Autotransplantation of teeth: Requirements for predictable success. Dent Traumatol 2002;18:157-180. 
8. Vilhjalmsson VH et al. Dental autotransplantation to anterior maxillary sites. Dent Traumatol 2011;27(1):23-9.
9. Park JH, Tai K, Hayashi, D. Tooth autotransplantation as a treatment option: A review. J Clin Pedia Dent 2010;35.(2):129-35. 
10. Bauss O, Zonios I, Rahman A. Root development of immature third molars transplanted to surgically created sockets. J Oral & Maxillo Surg 2008;66(6):1,200-11.
11. Honda M et al. Use of a replica graft tooth for evaluation before autotransplantation of a tooth. A CAD/CAM model produced using dentalcone-beam computed tomography. Int J Oral & Maxillo Surg 2010;39(10):1,016-9.
12. Andreason JO et al. A long-term study of 370 autotransplanted premolars. Part III. Periodontal healing subsequent to transplantation. Euro J Orthodont 1990;12(1):25-37.
13. Bauss O et al. Effect of different splinting methods and fixation periods on root development of autotransplanted immature third molars. J Oral & Maxillo Surg 2005;63(3):304-10.
14. Kim E et al. Evaluation of the prognosis and causes of failure in 182 cases of autogenous tooth transplantation. Oral Surg Oral Med Oral Pathol Oral Rad & Endo 2005;100(1):112-9.
15. Bauss O, Kiliaridis S. Evaluation of tooth position, occlusion, and interproximal contacts after transplantation of immature third molars. Euro J Ortho 2009;31(2):121-8. 
16. Paulsen HU, Andreasen J, Schwartz O. Pulp and periodontal healing, root development and root resorption subsequent to transplantation and orthodontic rotation: A long-term study of  autotransplanted premolars. Am J Ortho & Dentofac Orthoped 1995;108(6):630-40.
17. Paulsen HU, Andreasen J. Eruption of premolars subsequent to autotransplantation. A longitudinal radiographic study. Euro J Ortho 1998;20(1): 45-55.
18. Andreason JO et al. A long-term study of 370 autotransplanted premolars. Part IV. Root development subsequent to transplantation. Euro J Ortho 1990;12(1):38-50.
19. Kaku M et al. Cryopreservation of periodontal ligament cells with magnetic field for tooth banking. Cryobiol 2010;61(1):73-8.
20. Oh YH et al. Cryopreservation of human teeth for future organization of a tooth bank--a preliminary study. Cryobiol 2005;51(3):322-9. 
21. Lee SY et al. Effects of cryopreservation of intact teeth on the isolated dental pulp stem cells. J Endo 2010;36(8):1,336-40.
 
 
*Dr. Schmidt is a 2012 graduate of the University of Minnesota School of Dentistry. Email is Schmidt@uwalumni.com.
*Dr. Cleverly is a former attending surgeon at Gundersen Lutheran Oral and Maxillofacial Surgery program,currently purusing private practice in Lincoln, Nebraska. Email is  delevoms@hotmail.com.