Tooth autotransplantation 2: the interdisciplinary approach with emphasis on the orthodontic aspects

General considerations

As with any treatment, a thorough history is required to establish the concerns of the patient and family regarding whether treatment is likely to achieve the desired outcome. There are few medical problems that contra-indicate autotransplantation, although some conditions can make treatment difficult and complicated. For patients with bleeding disorders, poorly controlled diabetes, increased risk of bacterial endocarditis, a history of bisphosphonate use or malignancy, an opinion should be sought from their physician regarding suitability for treatment.¹ Allergies to materials used in dentistry, such as nickel or acrylate, may be managed through the use of alternative materials. The dental history is important for determining suitability and likely compliance with care, specifically, attitude to dental treatment, caries risk, history of trauma, previous treatment and any evidence of anxiety towards treatment. Finally, any habits should be identified. Behaviours that increase the risk of trauma to anterior teeth, such as digit-sucking and nail-biting, need to be completely stopped prior to starting treatment to prevent unnecessary additional forces to the transplanted tooth.

Need for tooth replacement

Members of the interdisciplinary team jointly assess the need for tooth replacement. Opinion regarding the prognosis of a failing tooth may be provided by paediatric or restorative dentists based on clinical and radiographic signs and symptoms. Advice on the interpretation of radiographic signs may be sought from a dental radiologist. Predicting the long-term survival of traumatized teeth can be difficult, and any uncertainties about prognosis should be articulated to the patient and family during the decision-making process. Where teeth are missing, the existing method of tooth replacement is assessed for appearance, function and the patient's perception of its success (Figure 1). Tooth replacement with transplantation is only indicated where it is expected to provide a better outcome than the existing solution. In cases where no tooth replacement is required or an alternative method is deemed more appropriate, autotransplantation may be eliminated as a suitable option and the patient should be referred to the appropriate care pathway. Alternative treatment options are discussed fully later in the fourth article in the series.

Suitability for orthodontic treatment

Suitability for orthodontic treatment is judged using the same criteria as for any other orthodontic patient, including dental health, oral hygiene, willingness to wear fixed appliances and ability to attend for appointments. It is essential that orthodontic treatment is judged to be beneficial and that the advantages of transplantation will outweigh the potential risk of increasing the length and complexity of orthodontic treatment. Orthodontic treatment need is assessed through routine extra-oral and intra-oral examination supported by special tests. An OPT provides an overall impression of the dentition and an indication of the stage of development of the donor tooth, bone height in the recipient site and the space available in the recipient site. A lateral cephalogram provides supplementary information to aid diagnosis and treatment planning. Additional 3D imaging, such as localized cone beam computed tomography (CBCT) techniques is often indicated to assess the donor tooth and recipient site in more detail. CBCT must be justified to aid diagnosis and inform the treatment plan² (Figure 2). The clinical assessment allows diagnosis of all aspects of the malocclusion and formulation of a list of treatment aims. If the patient has no orthodontic treatment need or is deemed to be unsuitable for orthodontic treatment, it is unlikely that autotransplantation is a suitable treatment option and other types of care should be considered. For those requiring orthodontic treatment, the next stage of treatment planning involves identification of a suitable donor tooth.

Availability of a donor tooth

Selection of the ideal donor tooth depends on the size of the recipient site and the desired coronal morphology of the tooth replacement (Table 2). The malocclusion may determine which teeth are extracted. Severely ectopic canine or premolar teeth that have been judged to be orthodontically unalignable may be considered as donor teeth but atraumatic removal can be challenging. In Class I malocclusions with crowding, or where space is required to recreate space for tooth replacement, extractions are often indicated. In these cases, consideration should be given to whether the extraction choice could provide a donor tooth. For Class I malocclusions without crowding and with adequate space for tooth replacement, it is unlikely that a donor tooth will be available (Figure 3). Class II malocclusions in growing patients may be treated by growth modification or orthodontic camouflage. In these cases, especially in the presence of crowding or significant incisor proclination, extractions are often indicated. Again, consideration should be given to extracting a tooth that could be used as a donor (Figure 4). Class III malocclusions requiring tooth replacement may be more challenging to plan, as it is often preferable to delay definitive treatment planning until future growth can be confidently predicted. In milder cases, amenable to camouflage, or cases with significant upper arch crowding, extractions may be planned. For those cases where treatment decisions must be delayed, it is important that space for tooth replacement is not lost.

Awaiting dental development

Autotransplantation has been shown to have the highest success when the donor tooth is transplanted when the root development is approximately 75% of expected length.³ However, if a very young patient loses a tooth due to dental trauma, an interim plan may be required. The aim of this treatment is to maintain space and to provide aesthetic and functional solutions, whilst awaiting dental development. The most common interim solution is a removable appliance with prosthetic teeth (Figure 5). Regular monitoring is essential to determine the ideal time for tooth transplantation and ensuring prompt care.

Pre-surgical orthodontics

Pre-surgical orthodontics aims to create adequate space for the transplant and address aspects of the malocclusion that requires correction prior to the surgery. The antero-posterior, vertical and transverse elements of the malocclusion must be considered, as these influence space requirements, anchorage demands and treatment timing and sequencing. This may include correction of a significant antero-posterior or vertical discrepancy or centreline correction to ensure that the transplant can be placed in the correct position. Fixed, functional or removable appliances may be used, depending on the planned tooth movements. Staged extractions may help to create space for the transplant, correct crowding or address centreline discrepancies. Overbite reduction may be required to ensure that the transplant will not be placed in a position with occlusal contact post-operatively. Additional anchorage may be necessary to maintain space in staged extractions, or in cases where the donor tooth choice complicates the orthodontic treatment (Figure 6).

Post-surgical orthodontic treatment

Following transplantation, it is recommended to wait a minimum period of 3–9 months prior to application of orthodontic force to the transplanted tooth. This is based on the guidelines for orthodontic treatment of avulsed teeth,^4,5 although the underlying evidence in this area is relatively weak. Anecdotal evidence from teams in Europe suggests that earlier application of forces, after 8 weeks, can reduce the incidence of ankyloses, but this has not yet been demonstrated by research. The rationale for the length of delay in force application is a balance between promoting healing of the pulp and periodontal ligament and enabling force application before complete alveolar bone repair. In addition, in immature teeth, it is expected that some continued root development would be seen in this period to confirm satisfactory healing. The type of movement required on the transplant may also influence the timing of force application, with extrusion movements being commenced earlier than rotation or bodily tooth movement.⁶ In the healing period, orthodontic treatment may be continued for the remaining dentition to address other aspects of the malocclusion efficiently (Figure 7).

All transplanted teeth should undergo regular clinical and radiographic examination throughout treatment to assess pulp health, root development and root resorption. This follows an agreed protocol to avoid duplication but to ensure adequate monitoring. There should be a high index of suspicion for ankylosis and any abnormal tooth movement should be investigated promptly. Donor teeth with closed apices at time of transplantation will require pulp extirpation and a definitive root canal treatment post-operatively. There appears to be no increased risk of orthodontically-induced root resorption in root-treated teeth and some studies have even shown reduced levels of orthodontically-induced root resorption with root canal treatment.⁷ It is expected that root-filled transplanted teeth would behave similarly. Teeth transplanted with an immature root and open apex are expected to continue root development, but a normal root length may not be reached and the effect of orthodontically-induced root resorption may therefore be more significant.⁸ Prior to completion of orthodontic treatment, it is advisable to remove the interim composite camouflage and reassess the position of the transplanted tooth with a restorative dentist, to confirm the precise restorative camouflage required and how orthodontic finishing may assist this (Figure 8). Alterations in tooth positioning can provide space for the restoration and improve the gingival contour. Placing a first-order bend in the orthodontic wire can inset the transplant so that minimal labial tooth preparation is required, thus improving the bond strength of the final veneer restoration. Retention is a key component of the orthodontic treatment and should be planned with consideration of the initial malocclusion, tooth movements and any future restorative treatment that is planned. Removable retainers may require replacement as the transplanted tooth is reshaped. Bonded retainers may be complicated by the morphology of the transplanted tooth and adhesion to any coronal restorations that have been placed.