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Nute SJ Severe incisor resorption by impacted maxillary canines: case report and literature review. Int J Paed Dent. 2004; 14:451-454
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FTTA in Orthodontics, Orthodontic Department, University Dental Hospital of Manchester, Manchester, M15 6FH and University Hospital of South Manchester, Wythenshawe, M23 9LT, UK
This case report highlights the benefit of Cone Beam Computed Tomography (CBCT) in the diagnosis of incisor root resorption. Management of a 13-year-old patient, who was referred for an orthodontic assessment of an unerupted maxillary canine which was in complete transposition with the upper lateral incisor, is discussed. CBCT highlighted root resorption of the lateral incisor, as well as the central incisor, and provided additional diagnostic information to that shown by plain radiographic films.
Clinical Relevance: To demonstrate the efficacy of CBCT in detecting incisor root resorption secondary to maxillary canine impaction.
Article
Impaction of the permanent canine occurs when its eruption is prevented by being embedded in the alveolus. Careful clinical and radiographic examination is required to identify impacted permanent canines; the optimal age for radiological investigation is 10–13 years.1 The incidence has been reported at 0.98–2.2%.2 Of impacted canines, 20% are buccally placed, with the remainder being positioned either palatally, or distal to the lateral incisor.3
Tooth transposition is a unique type of ectopic eruption in which two teeth have interchanged position in the dental arch;4 or there is development of a tooth in a position normally occupied by a non-adjacent tooth.5 The most common tooth involved is the maxillary canine.4 The aetiology is reported to be multifactorial, including both genetic and environmental factors. The prevalence is less than 1%.5
Incomplete transposition is a condition describing an interchange in the positions of the crowns of two permanent teeth within the same quadrant of the dental arch, while the root apices remain in their relative positions. Complete transposition is a similar situation in which both the crowns and the entire root structure are transposed.6
Root resorption of incisors (most commonly the roots of the lateral incisors) is one of the complications associated with impacted maxillary canines, and occurs in 7% of 10–13 year-olds.3 The reported incidence of resorption is 6–67%, depending on the type of imaging used.7
It is of fundamental importance to identify resorption of maxillary incisors as this impacts on orthodontic treatment as well as the prognosis of affected teeth. It is often difficult to diagnose resorption of maxillary lateral incisors on an OPT or intra-oral films, however, diagnostic accuracy is increased with the use of CBCT.8
Cone beam computed tomography (CBCT) has been used in dentistry since the 1990s.9 It is superior to conventional radiographs and can be justified to solve diagnostic problems in the best interests of the patient, despite additional radiation and cost.10 It overcomes problems of conventional radiographs, including distortion, overlapping, superimposition of structures and has the benefit of increased perceptibility of root resorption.8,9,10 3D imaging, proximity of impacted canines to adjacent incisors and other neighbouring structures, especially in the bucco-lingual plane, can be relatively easily evaluated qualitatively and quantitatively.7
One study has shown 12% of patients experiencing root resorption of the lateral incisors secondary to maxillary canine impaction, where plain film radiography has been used. This same study highlighted how CBCT allowed more accurate detection of incisor root resorption secondary to maxillary canine impaction; 38% of maxillary incisors and 9% of central incisors were affected.8,11
CBCT is useful for the following:
Imaging impacted teeth;
Dental abnormalities;
Assessment of alveolar bone height/volume and high diagnostic yield of tooth position.
Case report
A 13-year-old girl was referred for an orthodontic opinion regarding a retained URC and unerupted UR3. There was no history of dental trauma and no medical history of note.
The patient had a crowded Class III malocclusion with a mobile, worn URC and the unerupted UR3 palpable labially between the UR2 and UR1 (Figure 1).
Subsequent plain film radiographic examination showed complete transposition of UR3 with UR2 (midline of UR3 mesial to that of UR2) with advanced resorption of the URC root, obvious and advanced root resorption of UR1 with UL1 also displaying a shortened, blunted root (Figures 2 and 3).
The radiographic report obtained stated that there was no suggestion of resorption affecting the UR2. However, resorption of the distal surface of UR1 was apparent. At this stage, CBCT was unavailable in the unit; the decision was made to align UR3 in its correct position extracting URC and accepting that the long-term prognosis of UR1 was poor. The findings were explained to the patient and her parents with the additional advice that, as and when UR1 was lost, there would be a need for subsequent prosthetic replacement with either a bridge or implant. The funding situation in the region was such that there was no guarantee that the patient's PCT would approve funding for a single unit implant to restore the UR1 space.
As per recommended guidelines, where there is pre-existing root resorption a mid-treatment peri-apical of the UR1 region was taken as orthodontic alignment progressed. Upon distalization of the UR3, the root of UR2 became visible; the appearance of the root on plain film radiography gave rise to the suspicion of root resorption on its mesial aspect (Figure 4). The radiographic report confirmed the possibility of a resorption cavity affecting the middle third of the UR2 root probably arising from the mesial side. Pulpal involvement could not be excluded without further imaging. It was felt a CBCT was justified and would prove valuable in demonstrating the extent and exact site of resorption.
Figure 4. In-treatment periapicals giving rise to suspicion of UR2 resorption.
Fortunately, CBCT imaging had recently become available within the unit and the suggested examination was ordered. CBCT confirmed the previously detected distal root resorption of the UR1. Additionally, it demonstrated extensive external root resorption of the UR2, affecting the mesial and labial surface along the full root length with pulpal involvement. (Figure 5)
Figure 5. CBCT images showing the extent and site of UR1, UR2 root resorption.
Following these findings, the patient was seen at a hypodontia MDT clinic with restorative and oral surgery colleagues to discuss the long-term management of UR1 and UR2. The decision was made that the long span affected would not be amenable to restoration with conventional bridges; additionally, the patient had a well cared for virgin dentition making such extensive irreversible restorative treatment undesirable. The ideal method to restore the UR2 and UR1 spaces eventually would be by means of implant-retained prostheses. The patient's PCT was contacted with a detailed letter explaining the unusual circumstances, along with supporting evidence to justify eventual implant-retained restorations. The funding request proved successful.
Owing to the extent of resorption, UR2 was only passively engaged to sequential archwires during treatment, allowing the tooth to serve as a natural space maintainer. UR2 and UR1 remained asymptomatic throughout treatment. As such, the decision was made to maintain them in situ allowing alveolar bone and coronal space to be maintained for future implant placement. At the end of treatment, the position of UR3 to UL3 was maintained with a combination of bonded and removable retainers.
The patient was 16 at the end of orthodontic treatment; she would be kept under orthodontic review whilst in retention for one year. Following this, the processes for implant placement would proceed when UR2 and UR1 became symptomatic (Figure 6).
There is always the option to accept the position of a transposed tooth.5 In this case, it would have meant sacrificing the lateral incisor and aligning the UR3 in the UR2 position, followed by future restoration of the UR3 and UR1 spaces. Multidisciplinary management of this case resulted in a restorative opinion being gained from the outset. This opinion determined the UR3 should be aligned in its correct position for the optimal functional and aesthetic result, accepting future restoration of the UR2 and UR1 spaces with prosthetic replacements. Although distalization of UR3 and root uprighting did potentially lengthen treatment time, it also allowed actualization of the ideal long-term restorative goals.
Conclusion
CBCT allows more accurate diagnostic information to be obtained; this is essential in clinical decision-making and facilitating treatment planning to allow the best possible management of the orthodontic patient. It is especially advantageous in those patients with ectopic teeth and resultant resorption of adjacent neighbouring teeth.
