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Avulsion injuries are a severe type of dental trauma that can result in sequelae such as root resorption, ankylosis and tooth loss. We report on an unusual case where a previously avulsed, replanted and root-treated UR1 did not erupt for 3 years, and then spontaneously erupted. Findings from a small volume CBCT scan showed significant internal root resorption extending to the root wall, which supports an explanation of the internal root resorption removing an area of ankylosis and allowing the tooth to erupt. The value of using dental CBCT scanning is highlighted in managing complex dental trauma.
CPD/Clinical Relevance: The use of a small volume CBCT scan can give insight into the clinical presentation of post-traumatic tooth movement.
Article
Dental trauma is common and affects approximately one quarter of schoolchildren worldwide.1 Findings from the Children's Dental Health Survey 2013 reported that, on average, one in 10 children had sustained previous dental trauma of their upper incisors.2 Almost twice as many boys (11.2%) presented with any traumatized incisors compared with girls (6.9%).3
An avulsion injury, where the tooth is completely knocked out of the mouth, accounts for 0.5-3% of all dental trauma to permanent teeth.4 A significant risk for an avulsion injury is healing by ankylosis, whereby a union between tooth and bone occurs due to the absence of the periodontal membrane. The risk of ankylosis can be estimated at 90% in cases of avulsion injuries with greater than 30 minutes’ dry time, or greater than 90 minutes’ total extra-alveolar time. Owing to their complexity, a multidisciplinary setting is often best suited for management of such cases.5 Effective management of dental trauma is important for function, aesthetic and social wellbeing. A negative association between untreated dental trauma and quality of life has previously been reported.6
The effective radiation dose, a quantity with direct correlation to biological risk,7 for a peri-apical radiograph is between 1 μSv and 8.3 μSv.8 Although the European Commission provide a range on the effective dose of small volume cone beam computed tomography (CBCT) scans for children at 16-214 μSv,9 the large exposure range makes it difficult to generalize the radiation doses from CBCT scans. A metaanalysis published in 2015 provides a comparison of the effective doses for nine CBCT units based on the varying field of view sizes.7 It is important for clinicians to be aware of the range of radiation dose from the CBCT unit being used to make an informed decision on whether taking such a scan is justified. Some newer models have reduced the effective dose for a standard exposure, for example in one unit using 8 x 8 cm field of view CBCT, the effective dose was reduced by 57% following the use of 0.5 mm of additional copper filtration compared with an earlier model of a manufacturer's unit.10 Furthermore, a 20-fold range of effective dose for dental CBCT scanners was found in another study, encouraging optimization of dose through appropriate selection of exposure parameters and field of view size.11 The CBCT machine used in this reported case was the 3D Accuitomo 170 (J Morita, Japan), with the child phantom 4 x 4 cm maxilla ‘standard’ scan reported as 28 μ5ν.7 Modern radiation doses can be even lower, such as that of the 0P300 Maxio CBCT scanner (Instrumentarium Dental, Finland) with the child effective dose of a 5 x 5 cm maxilla scan reported as 16 μSv12 and the CS 9000 scanner (Carestream Dental, Atlanta, GA, USA) child phantom 4 x 5 cm maxilla dose reported as 16 μSv.7
Figure 1. Peri-apical radiograph of UR1 taken in November 2020.Figure 2.
(a-c) Clinical photographs taken in February 2021.
Clinical case
Initial presentation
A medically fit and healthy 11-year-old male presented on the joint orthodontic-paediatric clinic at the Royal National ENT and Eastman Hospital in November 2020 with concerns about his ‘short upper right front tooth’. The patient presented with a Class II division 1 malocclusion and a history of dental trauma to the upper right central incisor (UR1). The UR1 was avulsed in a skiing accident 3 years prior to presentation, in 2017, and had previously been replanted and root treated.
On examination, there was an additional finding of molar-incisor hypomineralization (MIH) affecting the UR6, UL6 and LR6, but otherwise no obvious pathology apart from the traumatized incisor. The incisal edge of the UR1 was 4.5 mm more gingival than the incisal edge of the UL1 and the gingival margin of the UR1 was 1.5 mm more apical than that of the UL1 (Figure 5a). The upper incisors were not tender to lateral or vertical percussion, not mobile, not discoloured and not associated with pain or any sinus or abscess. The percussion tone of the UR1 sounded normal in relation to the adjacent incisor teeth. The UR1 was negative, while UR2, UL1 and UL2 were positive to ethyl chloride sensibility testing.
The patient's family had noted that the position of the UR1 had not changed since the tooth was replanted in 2017. Radiographic investigation using a periapical radiograph (Figure 1) revealed the UR1 had a short root filling and a radio-opacity consistent with restorative material within the root canal system. The periodontal ligament space was visible in most, but not all, areas around the root, indicating potential areas of ankylosis.
Clinical records
Following full records, including clinical photographs (Figure 2), orthopantomogram and lateral cephalogram in February 2021, a small volume CBCT of the UR1 was requested to assess for ankylosis and pathology. Multiple cancelled appointments resulted in a delay of patient care. Figure 3 shows different views captured using the small volume CBCT taken in June 2021. The CBCT images show significant internal root resorption of the previously avulsed and root-treated UR1, extending to the root wall of the tooth.
Reassessment
Figure 3. Axial, coronal and sagittal views of the UR1 showing extensive internal resorption.
Interestingly, when the patient attended for treatment planning in September 2021, he had noted that over the previous 2 months the UR1 had gradually ‘come down into the mouth’ and not caused pain or infection (Figures 4 and 5). The UR1 incisal edge was 1 mm more gingival than the incisal edge of the UL1; the UR1 had erupted by 3.5 mm since initial presentation. Furthermore, there was a significant improvement in the gingival margin height. The UR1 was nonmobile, not tender to percussion and there was no evidence of an abscess, swelling or sinus tract. Slight grey discolouration of the UR1 was noted. While initially the preferred plan was to attempt orthodontic extrusion and alignment of the UR1, the patient and family were now happy with the appearance of this tooth. Following discussion of the treatment options, the patient and parents decided not to undertake any orthodontic intervention and accept that the UR1 is likely to be lost in the future and require replacement.
Figure 4. Frontal photograph taken in September 2021.Figure 5. Photographs taken in (a) February 2021 and (b) September 2021 showing the relationship between UR1 and UL1.
Discussion
How did the UR1 spontaneously erupt after 3 years of no movement?
A postulated cause of eruptive movement of the UR1 is due to an area of previous ankylosis between the root and alveolar bone being freed up due to the internal resorption extending to the root wall. This would explain why the UR1 had not been mobile, but had gradually erupted over a few months. Another possible explanation of this delayed eruption may be that there was a root fracture at the point of the resorption: however, this is likely to have resulted in a sudden tooth movement and mobility of the coronal aspect of the UR1, which was not the case in this patient.
This case demonstrates the value of a small volume CBCT scan, which allowed the comprehensive assessment of both the root system and the relationship between the tooth and alveolar bone. The CBCT images clearly illustrated the extent of internal root resorption to the root wall, and therefore aided in understanding the likely cause of the unusual spontaneous eruption of the UR1 and its poor long-term prognosis.
Should small volume CBCT scans be taken in all dental trauma cases?
The authors do not advocate taking small volume CBCT scans in all cases of dental trauma, particularly during the immediate management, which is often time dependent. However, the authors do suggest use of small volume CBCT scans during the medium-to long-term management of complex dental trauma cases, such as root fractures, avulsion and luxation injuries. The comprehensive investigation can aid decision making for the most effective treatment plan. In all cases, a risk-benefit analysis should be considered, with the risks of missing important diagnostic and prognostic information from a two-dimensional radiograph compared with the risks of exposure to small volume CBCT scanning.
Conclusion
The limitations of conventional radiographs that provide two-dimensional views of three-dimensional objects should be appreciated.
In cases where an ankylosed tooth has spontaneously erupted, consideration should be given to the possibility of significant internal resorption removing the area of ankylosis.
Use of small volume CBCT scans should be considered in cases of complex trauma to allow visualization of the crown, root, root canal system, and the relationship between the tooth and surrounding structures in three dimensions.
