The diagnosis and management of invasive cervical resorption

Case report

A 23-year-old Caucasian female patient was referred by her general dental practitioner to a University teaching hospital. She reported hypersensitivity to hot and cold stimuli in relation to LR4.

Clinical examination revealed no caries or loss of tooth structure associated with this tooth. A ‘pink spot’ was, however, noted on the buccal aspect of the tooth (Figure 1). This type of colour change is usually associated with the degradation of blood cells within the dentine.9 The tooth was not tender to percussion and there was no buccal swelling present. The periodontal probing depths were within normal limits and there was no evidence of mobility. A conventional radiograph revealed a radiolucent area on the mesial aspect at the cement-enamel junction, but there was no evidence of a periapical radiolucency (Figure 2). These radiographic findings suggested external resorption. Prior to deciding on a treatment plan, a decision was made to obtain a low volume CBCT image (Accuitomo, Japan) of this region. The CBCT image revealed a 1.5 mm cavity at the mesio-lingual cervical margin of LR4. This extended in a channel of demineralization to the pulp. There was a substantial loss of dentine on the mesial aspect of the LR4 crown extending up to the amelo-dentinal junction and down to the pulp. The root canal was patent and there was evidence of periapical widening of the periodontal ligament which was not detected on the conventional radiograph. There was also an incidental finding in relation to LR6 which exhibited a surface defect of the distal aspect of the distal root about 1.4 mm below the amelo-cemental junction. The root canals were patent (Figure 3).

A definitive diagnosis of ICR was made and the patient informed accordingly. The patient was advised that the prognosis of LR4 was guarded owing to the extent of the resorptive lesion. It was decided to retain the tooth as the only other option was an extraction. The patient had excellent oral hygiene and was highly motivated to preserve the tooth.

The LR4 tooth was isolated with rubber dam. It was not clamped to minimize the likelihood of crown fracture. Instead, LR5 was clamped to secure the rubber dam. Coronal access was carried out under x3 magnification to facilitate adequate visualization of the resorptive lesion and the canal space. The pulp was extirpated. The pre-operative radiograph was used to estimate the working length and a further radiograph was taken with a size 20 K file, placed into the canal, to confirm the length (Figure 4a). The canal was prepared with protaper rotary instruments to size F3 (Protaper, Dentsply, Maillefer, Ballaigues, Switzerland). This was accompanied with copious irrigation with 1.0% sodium hypochlorite. A periapical radiograph was exposed with a custom-fit F3 gutta-percha point (Protaper Universal GP, Dentsply, Switzerland) in the canal (Figure 4b). System B (SybronEndo, Orange, CA, USA) was used for warm vertical compaction of the apical third of the gutta-percha after lubricating the canal with root sealer (AH plus, Dentsply, Germany). The remainder of the canal was back-filled with thermoplasticized gutta-percha (Obtura, Spartan, USA). A final radiograph of the obturation was taken and revealed a very satisfactory treatment (Figure 4c). The access cavity was sealed with glass ionomer cement (GC Fuji IX, Japan).

After 7 days, the patient was seen again. She reported a significant improvement in her symptoms. The hypersensitivity symptoms to hot and cold stimuli had disappeared. On clinical examination, the pinkish discoloration of the buccal aspect of the crown had changed to a grey colour (Figure 5a). At this visit, the provisional restoration was removed under rubber dam isolation. An area of bleeding was seen under magnification (Figure 5b). The decalcified dentine was carefully and completely removed with slow-speed long shank burs (Dentsply, Switzerland). This was carried out with copious irrigation with 1.0% sodium hypochlorite. The communication between the pulp space and lingual surface of LR4 was located (Figure 5c). The bleeding resulting from the perforation was successfully arrested and sealed with a thin layer of light-cured resin modified glass ionomer (RMGI) (VitraBond, 3M ESPE, Bracknell, UK) (Figure 5d). The crown was then built up with a composite restoration (Enamel Plus, HFO, Germany) (Figure 6). The patient was reviewed 3 weeks later and the tooth was completely symptom free and had regained its natural shade. She was travelling abroad for a 3-month period. A further appointment was planned for her return to review LR4 and commence possible root canal treatment on LR6.

Discussion

Cone Beam Computed Tomography proved essential for the diagnosis and treatment of this patient. It revealed the extensive nature of the resorptive lesion, as well as an unexpected lesion in LR6. The findings were considered very unusual as the patient had a well maintained dentition.

Although the aetiology of this type of resorption remains uncertain,9 some potential factors include trauma, orthodontic treatment and internal bleaching.15 The patient did not report any history of trauma. Internal bleaching did not arise as none of her teeth was root-filled. She had, however, received a course of fixed orthodontic treatment in her teens. The patient presented with two resorptive lesions. Genetic predisposition and systemic disease have been shown to be associated with multiple resorptions.16^,17

Hyperplastic invasive resorptions can have a pulpal (internal) or periodontal (external) origin.9 Treatment protocols for internal and external resorption are different. The main difference is that, for internal resorption, root canal treatment is necessary whereas, in external resorption, root canal treatment can be avoided, depending on how advanced the lesion is. Central to the management/success of treatment, therefore, is the correct diagnosis so that the appropriate protocol is followed. In the case report described here, CBCT proved to be an essential diagnostic tool confirming ICR in LR4. The extent of the resorptive lesion in LR4 and its communication with the pulp could not be fully assessed on the conventional periapical radiograph.

Additionally, there was also an incidental finding of ICR in relation to the distal root of LR6, which again was only detected on the CBCT image. The effective dose of the low volume cone beam image used is of the order of 0.025 mSv. This is equivalent to about one week of natural background radiation, which is negligibly small in terms of radiation exposure.

Treatment of ICR with topical application of 90% aqueous trichloacetic acid, curettage and restoration of the affected teeth without root canal treatment has been reported by a number of investigators.18^,19 In this particular case, the patient complained of symptoms with hot and cold stimuli in relation to LR4. There was no evidence of a periapical radiolucency on the conventional radiograph of LR4. The CBCT image, however, revealed some apical widening of the periodontal ligament. ICR was at an advanced stage in this case. The CBCT image demonstrated a channel of demineralization communicating with the pulp. Owing to the obvious pulpal involvement and the patient's clinical symptoms, a decision was made to carry out root canal treatment and a radical treatment approach was pursued. It was imperative to remove all the resorptive tissue to avoid the recurrence of the lesion and the risk of subsequent loss of the tooth. The resorptive lesion was repaired internally with the aid of a microscope. The materials commonly used to repair progressive root resorption include glass ionomer, RMGI and Mineral Trioxide Aggregate (MTA). RMGI was chosen in this case as the defect was relatively large and cervically located. Additionally, RMGI also offers better fracture toughness and wear resistance compared to, for example, MTA. MTA is not a hard material and therefore cannot reinforce the tooth structure. Furthermore, RMGI is tooth-coloured and does not stain.20

The alternative treatment option was extraction of LR4 and provision of either an adhesive bridge or an implant. Provision of an adhesive bridge was discarded on aesthetic grounds. The patient was well motivated and had good oral hygiene. She was keen to save the tooth and avoid an implant. As well as the advantage of retaining her natural tooth, root canal treatment was also the most cost-effective option.

The LR6 tooth was symptom free. The resorptive lesion will, however, require intervention. The CBCT image revealed an area of demineralization occupying the dentine disto-buccally. This, in turn, connected with the distobuccal pulp horn. Unlike LR4, the treatment on LR6 may involve removal of the resorptive lesion first and possible preservation of pulp vitality. A number of authors21^,22 have reported the use of MTA as a pulp-capping material to preserve the vitality of the pulp. It has been shown that an inflamed, but vital, pulp of permanent teeth may have a chance to return to a healthy functional status after MTA pulpotomy.

ICR is an uncommon occurrence. In this case, the root canal treatment was satisfactory and the patient was pleased with the final restoration/aesthetic result. The decision to retain LR4 was justified in such a young patient.