Challenges in treating traumatically intruded and ankylosed permanent incisors: a case report with a multidisciplinary approach

Intrusive luxation defines an injury where a tooth is displaced axially into the alveolar socket.¹ As described in the literature, this causes both shearing stresses and compressive forces which result in extensive damage to the gingival fibres, periodontal ligament, apical tissues and alveolar socket wall.^2,3 As such, it is perhaps the most severe injury to the dentition with the healing process dominated by complications including:

Whilst pulp necrosis and inflammatory root resorption can, in most cases, be managed by endodontic therapy with calcium hydroxide,⁴ there is no effective treatment to date for replacement root resorption or ankylosis. Pathogenesis involves competitive wound healing processes between bone marrow-derived stem cells destined to form bone and periodontal ligament–derived cells programmed to form periodontal ligament fibres and cementum.

As healing occurs almost exclusively by cells from the alveolar wall, the root is gradually resorbed and replaced by bone, leading to eventual tooth loss.⁵

It has been shown that the extent of intrusion and the stage of root development are linked to the probability of replacement resorption, with shallow depth and immature root formation reducing the likelihood of ankylosis.² As these parameters cannot be modified, however, it is essential to employ the treatment method most likely to minimize the risk of replacement resorption. Although some authors suggest that the repositioning procedure has little effect on periodontal healing,⁶ others have shown that the treatment method used is related to the likelihood of future replacement root resorption.^3,7

A recent retrospective study of 51 intruded permanent incisors in Norwegian children sought to identify the treatment method least likely to result in replacement resorption. All ankylosed teeth in the study were lost by the end of the mean observation period of four years.⁸ The occurrence of healing complications with respect to the treatment modality were analysed and it was found that only 5% of teeth that were allowed to re-erupt spontaneously underwent replacement resorption, compared with 29% of both orthodontically and surgically repositioned teeth, concluding that the best treatment in 6–12 year-old children is to await re-eruption.

This is in agreement with the current guidelines,^9,10 which recommend spontaneous repositioning for all teeth with incomplete root development regardless of the severity of the injury, followed by orthodontic repositioning if no movement is noted within three weeks. It is noteworthy to mention that complete apical closure in upper permanent central and lateral incisors – which are the teeth most commonly involved in intrusive injuries¹¹ – does not occur until 13 years and nine months and 13 years and seven months of age, respectively.¹²

Andreasen et al³ have suggested treatment guidelines based on a combination of the stage of root development, age and severity of injury: the treatment of choice for the teeth with immature root development in 6–11 year-old children or mature root formation in patients aged 12–17 years is to await spontaneous re-eruption, although for intrusive injuries exceeding 7 mm, a surgical approach may offer some advantages in terms of endodontic access in particular. On the other hand, spontaneous eruption is not expected to occur in patients over 17 years of age and orthodontic or surgical repositioning is advised. Of these, a surgical approach is favoured as the benefit of slightly better marginal bone healing in orthodontic repositioning is outweighed by the disadvantage of it being significantly more time consuming, as illustrated by an increased number of visits required for treatment.³ Overall, conflicting evidence has been presented in the past with some authors recommending surgical repositioning^13,14 and others favouring an orthodontic approach.¹⁵ Indeed, as intrusive luxation has a low prevalence of 0.3–1.9% of all cases of dental trauma,¹ no randomized controlled trials exist to compare the three treatment alternatives.

Regardless of the method of treatment for intrusive injuries, results indicate that a proportion of teeth will become ankylosed and pose an extra challenge for management. Mild to moderate intrusion in patients whose alveolar growth is almost finished can be restored with a composite build-up, yet most injuries occur in children aged 6–12 years¹¹ where it is accompanied by infraocclusion of the tooth and lack of development of the alveolar ridge, thus complicating any orthodontic or prosthetic treatment in the future when the tooth is eventually lost.¹⁶

One suggested approach to this problem is decoronation which allows continued alveolar development and facilitates later prosthetic replacement.¹⁷ It involves raising a mucoperiosteal flap and sectioning the crown from the root with reduction of the coronal part of the root surface to a level 2 mm below the marginal bone. This has been shown to increase the vertical height of the alveolus if carried out before the age of 13 years, and maintain the facio-palatal dimension in all patients, thus facilitating implant placement at the appropriate time.

Other available options have been summarized by Sigurdsson.¹⁶ These include early extraction of the ankylosed tooth followed by prosthetic replacement of some type. Unfortunately, this results in the collapse of the buccopalatal plate creating a challenging osseous defect. Extraction and orthodontic space closure or autotransplantation can be ideal for children who have crowding. However, this can only be performed at a suitable stage of dental development. Surgical extraction of a minimally ankylosed tooth followed by re-implantation is a high risk option for a patient near the end of growth,¹⁸ whereas surgical block movement should only be used for fully grown patients with mild to moderate infra-position. The block containing the cortical plate, tooth and surrounding bone can either be repositioned into the new position or moved slowly into position with a distractor over several weeks. As outlined by Nörholt and Schwartz,¹⁹ the aim of alveolar distraction osteogenesis is to reconstruct bone and soft tissue, the attached gingiva in particular, in order to optimize the aesthetics of dental implants in the region of anterior maxilla and mandible.

Indeed, whilst some of these methods can prolong the survival of the tooth in the short to medium term, the ultimate goal is to create as good foundations as possible for the long term tooth replacement, as an ankylosed root will continue to resorb and be replaced by bone. As such, there is no perfect treatment for replacement root resorption as the ideal would be to reverse the process of ankylosis and retain the tooth. A literature search identified one earlier case report, where this occurred unexpectedly, and an intruded and ankylosed central incisor re-erupted in the two months following a crown-lengthening procedure.²⁰ Another article²¹ reported considerable acceleration of re-eruption after gingivectomy and root canal debridement and, indeed, the removal of scar tissue from around the tooth is sometimes recommended to facilitate re-eruption.¹ However, no studies have been carried out to investigate whether mechanical disruption from drilling or ultrasonic debridement could be an aetiological factor contributing to the spontaneous re-eruption of ankylosed tooth. Should this be the case, such an approach could provide a minimally invasive and conservative pathway to treat an ankylosed tooth and avoid the devastating sequelae of no treatment or from other treatment modalities. The following report describes a case where this is suspected to have contributed to the unusual re-eruption of a severely intruded and ankylosed upper lateral incisor.

Case report

A 12-year-old boy attended as an oro-dental trauma casualty, having fallen over a banister at home in February 2008, suffering extensive damage to his permanent anterior teeth. The trauma involved a displaced lower labial segment, an avulsed UR2, displaced UR1 and UL1, and intruded UL2, along with severe soft tissue injury where the mucosa was stripped from the gingival areas in both upper and lower incisors. The UR2, UR1 and UL1, as well as LR2, LR1, LL1 and LL2 were repositioned and splinted and a follow-up appointment arranged in the department of paediatric dentistry where the teeth were monitored clinically and radiographically over a series of appointments. Despite the extent of the injury, there was little evidence of damage to the roots and only the LR2 lost vitality and required root canal treatment. The major challenge, however, was the intruded UL2.

Following an initial partial re-eruption that occurred in the first few weeks after the accident, the UL2 was suspected to have ankylosed. This diagnosis was made due to the lack of any futher re-eruption, and the clinical sign of a metallic tin cup sound on percussion and the lack of mobility on manipulation. In spite of the guarded prognosis, it was decided to attempt to align the UL2 using an upper removable appliance and elastic traction on a bracket bonded to the UL2. This treatment was provided four months after the accident, however, it failed to facilitate forced re-eruption and the bracket was eventually removed in August 2009. As the patient was found to lack adequate oral hygiene and indeed commitment for complex orthodontic treatment, he was referred to a joint orthodontic-restorative clinic for advice regarding UL2 and options for replacement. The patient was seen in January 2010 with the initial plan to trim the incisal edge of the UL2 with a view to leaving the tooth in situ and encouraging gingival overgrowth by stimulating bleeding, followed by a resin-bonded bridge cantilevered off the UL1. A periapical radiograph (Figure 1) taken at this appointment indicated the lack of a distinct lamina dura in the apical third of the root, re-affirming the clinical diagnosis of ankylosis due to replacement resorption. Figures 2 and 3 show the UL2 before and after trimming. At the review appointment four weeks later the gingivae had almost healed over (Figure 4). The UL2 was reduced further (Figure 5) and a 3-month follow-up was arranged to see if any further soft tissue coverage would take place. Surprisingly, however, on the next appointment in May 2010, three months later, the UL2 was found to be erupting into the mouth, and was left for another six months when it had erupted to two-thirds of its full crown height (Figure 6). At this stage it was decided to restore the tooth with directly bonded composite resin, and following two failed appointments, the UL2 was finally built up in March 2011. It was first restored to the same dimensions as its contralateral counterpart in anticipation of possible further re-eruption (Figure 7), however, the patient disliked the appearance due to the lack of tooth showing, and the length of the UL2 was increased to provide more symmetrical level of incisal edges despite the excessive vertical crown height (Figure 8).