Complications after autotransplantation of a maxillary canine: a case report and literature review

The permanent maxillary canine has a pivotal role in facial and dental aesthetics, occlusion, lip support and phonetics. Second to the third molar, the permanent maxillary canine is the second most frequently impacted tooth, with a prevalence of 1.5%. Of these, literature states that 85% are palatally impacted and 15% labially impacted.¹

Autotransplantation is the positioning of a tooth in the same individual, from a donor site to an extraction site or a surgically prepared socket, and remains a documented alternative treatment option for managing impacted canines.² Autotransplantation of teeth has been carried out for many years globally with varying degrees of success. The earliest well-documented case was in 1954 by ML Hale, with some principles of his technique still followed today.³ In the last 30 years, the work of Andreasen et al, in conducting long-term studies of autotransplanted teeth, has been pivotal in establishing a protocol for this treatment.^4,5,6 With the development of new technologies however, dental autotransplantation is not typically an option contemplated immediately, but is considered useful in several clinical scenarios that are discussed later in the article. The traditional treatment options for managing impacted canines include: interceptive removal of the deciduous canine; surgical exposure with orthodontic traction; or surgical removal with a combined orthodontic–restorative approach. Thus, canine autotransplantation is not routinely considered unless the traditional modalities are deemed inappropriate or prove to be unsuccessful.⁷ The procedure is highly technique-sensitive. Careful attention to treatment planning in selected patients, along with thorough understanding of the biological concepts of healing, is essential for favourable prognosis.

Early studies revealed inadequate long-term results of this modality, with high rates of root resorption. However, recent studies that have adopted meticulous atraumatic surgical technique, and the stabilization of the transplanted tooth with a sectional archwire for 6 weeks have yielded better results.⁸ With significant long-term complications, including root resorption, cyst formation and ankylosis, there are several factors clinicians should consider prior to treatment planning.

This case report outlines a delayed complication in a 55-year-old male patient, presenting 35 years after autotransplantation of a palatally impacted canine.

Case report

A 55-year-old male patient was referred to an oral and maxillofacial surgeon by their general dental practitioner (GDP) owing to a chronic intra-oral swelling around the maxillary alveolus in the upper left canine–premolar region.

Upon further questioning, the patient revealed that he had had a canine transplant over 35 years previously owing to a palatally impacted canine in the upper left quadrant. The transplanted canine later became non-vital several months after transplantation, and was root filled, following which it remained asymptomatic. However, 25 years later, the patient reported the development of a chronic swelling associated with the tooth. Owing to the small size and asymptomatic nature of the swelling, the swelling was monitored conservatively for 10 years prior to the time of presentation to the maxillofacial team.

Medically, the patient had a mitral valve replacement, and was not on any regular medication. He was an ex-smoker and occasionally drank alcohol. He worked as a civil engineer.

On clinical examination, there was a swelling that was bony on palpation located around the maxillary alveolus at the upper left canine–premolar region. The upper left canine and adjacent teeth were not tender to percussion or mobile, and there was no suppuration on sulcular probing.

A panoramic and cone beam CT scan (CBCT) showed a peri-apical radiolucency extending palatal to the upper left canine suggestive of an inflammatory odontogenic cyst (Figure 1). There was evidence of both internal and external resorption of the canine root with extensive bone resorption.

Considering the clinical and radiographic findings, the patient underwent exploration and enucleation of the cyst, and surgical removal of the upper left transplanted canine.

Surgical approach

A buccal muco-periosteal flap was raised between the upper left lateral incisor to first premolar, and the upper left canine was extracted. Existing bony resorption of the maxillary alveolus had created a fenestration into the cystic cavity, and the cyst was enucleated. After curettage, the surgical site was packed with an absorbable haemostat and the mucoperiosteal flap sutured (Figure 2).

The histopathological examination of the cystic specimen associated with the transplanted upper left canine confirmed features consistent with a peri-apical cyst. Post-operative review of the patient confirmed a favourable surgical outcome and resolution of the patients' discomfort.

Discussion

Although transplantation is not the first-line treatment modality for patients with impacted canines, the current literature reports favourable outcomes.

In their systematic review and meta-analysis of the literature, Grisar et al reported an 87.5% survival rate of transplanted maxillary canines at follow up of 2–5 years, and an 88.2% survival rate at follow-up of over 5 years. However, when comparing the outcome rates of studies, it is important to consider the differing criteria for success used between studies.⁹ In 2019, Grisar et al incorporated established criteria for clinical assessment of transplanted teeth. The survival rate of transplanted maxillary canines, with an average follow up of 21 years was 67.9%, with a mean survival of 15.8 years.¹⁰

Autotransplantation offers a biological alternative to osseo-integrated implants and other fixed restorative options. The facilitation of a biological tooth and periodontal environment ensures the provision of proprioception during function.¹¹ Furthermore, there is potential to induce alveolar bone growth, and erupt with neighbouring teeth during continued facial skeletal growth, while permitting orthodontic movement.^12,13 Therefore, it provides an opportunity for aesthetic rehabilitation in growing individuals, unlike osseointegrated implants.

The healing outcomes are parallel to those for re-implanted traumatically avulsed teeth and, therefore, carry the risk of post-operative complications, including pulp canal obliteration, pulp necrosis, root resorption and ankylosis with replacement resorption, which can eventually lead to tooth loss. A progressive loss of transplanted teeth is to be expected with increasing follow-up time, since it has been shown that with increasing time after transplantation, significantly more root resorption can be expected.¹⁴

Factors that should be considered when selecting appropriate cases are explored in Table 1. The sequelae of complications can have a significant emotional burden, financial implications, treatment fatigue and impact on the patient's oral health-related quality of life.

Complications are more likely to occur in teeth with complete root formation with reduced regeneration potential. In contrast, more favourable outcomes are seen with transplanted canines with open apices, with up to two-thirds of root development.¹⁵ Dependent on the stage of root development (ie three-quarters of root formed), the transplanted canine may require root canal therapy within 10 days of transplantation.³ This will reduce the incidence of inflammatory resorption as a consequence of an infected root canal.¹⁶ Alternatively, endodontic treatment can be performed during the surgical transplantation procedure when longer splinting periods are estimated.

There are several intra-operative determinants of treatment success. The presence of an intact and viable periodontal ligament (PDL) on the root surface of the transplanted tooth is a vital factor.¹⁷ Andreasen et al described a regimented protocol for maxillary canine transplantation to ensure an atraumatic surgical approach, to facilitate optimal PDL regeneration.¹⁸ PDL healing can be impaired by exposing the root surface of the transplanted tooth.¹⁹ With compromise of cementum and PDL regeneration by bone or soft tissue defects, unfavourable consequences include periodontal pocket formation and inflammation, ultimately causing treatment failure.²⁰ It has been found that in cases where the PDL has been traumatized, external root resorption and ankylosis often ensues.

Creating a soft tissue barrier provides a defence against bacterial infiltration and facilitates PDL regeneration.²¹ Therefore, tightly suturing the keratinized mucosa around the transplanted tooth intra-operatively prevents leakage of oral fluids onto the transplanted tooth root.²² Furthermore, the addition of periodontal surgery into treatment planning ensures root coverage, prevention of hypersensitivity and carious/noncarious cervical lesions, and favourable aesthetics. Various systematic reviews have confirmed the gold standard for root coverage is a coronally advanced gingival flap combined with a connective tissue graft (CGT). Literature has shown that CGT addition facilitates less soft tissue shrinkage and increased keratinized tissue.^23,24

Accurate imaging modalities are further determinants of treatment success. CBCT facilitates planning surgical feasibility and optimal 3D positioning of the donor tooth.²⁵

It is difficult to determine the criteria for success of autotransplantation of impacted canines because the transplanted tooth may remain in situ for a considerable time with undiagnosed pathology before causing symptoms as there is maintenance of functional and aesthetic satisfaction. Further long-term studies are required to establish the long-term survival and success of autotransplanted impacted canines. This can be achieved with regular recall periods with appropriate imaging.

Conclusion

Autotransplantation of impacted permanent maxillary canines can be indicated in selected individual cases. Meticulous case selection and knowledge of prognostic factors, and appropriate management of patient expectations are essential. There is sufficient clinical experience to justify transplantation of maxillary canines as a legitimate treatment alternative when indicated. However, there is scope for further research to include larger samples and high-quality observational studies to improve the evidence-base.