Clinical technique for invasive cervical root resorption.

This clinical case report describes the diagnosis and treatment of an external invasive cervical resorption. A 17-year-old female patient had a confirmed diagnosis of invasive cervical resorption class 4 by cone beam computerized tomography. Although, there was no communication with the root canal, the invasive resorption process was extending into the cervical and middle third of the root. The treatment of the cervical resorption of the lateral incisor interrupted the resorptive process and restored the damaged root surface and the dental functions without any esthetic sequelae. Both the radiographic examination and computed tomography are imperative to reveal the extent of the defect in the differential diagnosis.

INTRODUCTION

An external root resorption mainly occurs when the protective pre-cementum layer is mechanically damaged or removed which allows for the denuded areas of the root surface to be colonized by clastic cells and for the resorption to get progressively worse.[1-3] An external invasive cervical resorption (EICR) is a type of external resorption that is unusual and very aggressive.[4] The etiology is unknown, but there are several predisposing factors that are related to the injuries from resorption, orthodontic movement, dentoalveolar surgery, orthognathic surgery, periodontal treatment and tooth whitening procedures, alone or combined.[125] This kind of resorption usually develops very slowly and it is initially asymptomatic and is sometimes found in a routine radiographic examination. Although early diagnosis can be difficult, some clinical signs may suggest the presence of resorptive process, such as a rosacea-like discoloration of the tooth, discrete contour irregularities with or without gingival bleeding on probing, and in more advanced cases, the adjacent periodontium presenting edema due to secondary infection. The radiograph may show a radiolucent area in the demarcated root structure by a thin radio-opaque line that matches the outlines of the canal area overlapping the irregular external resorption which may be associated with a slight irregularity in the adjacent bone-crest.[67]

The progression of EICR starts from a small point of entry of granulomatous tissue in the cervical area towards the apical or crown portion. The extent of the resorptive defect inside the tooth can be used to classify the lesions from levels 1 to 4.[5] This classification is important for deciding on the treatment and making a good prognosis. The EICR Heithersay's class 1 denotes a small invasion area of granulomatous tissue with shallow penetration in the dentin. In class 2 injuries, a well-defined invasive resorption area is visualized extending into the coronal pulp and may or may not involve the dentine. Class 3 resorption is characterized by a deep invasion of the dentin by the resorption tissue, not only involving the dentin disease, but also the root's crown third. Class 4 resorptive lesions have a broad process of resorption extending into the apex, surpassing the cervical third of the root.[7] Several proposed treatments all consist of exposing the resorption area to eliminate the granulomatous tissue responsible for the injury.[53] However, after debridement, the choice of a restorative filling for the remaining cavity remaining would differ according to the recommendation for each specific case. Glass ionomer cement, composite resin, amalgam, and mineral trioxide aggregate (MTA) have been suggested as possible restoratives.[48] This recommendation is based on the position of the remaining resorption cavity. If it is supragingival, the material needs to be restorative, aesthetic, and functional; if it remains subgingival and supra-osseous, the glass ionomer and the MTA may be indicated. When the resorption lacunae remain sub-osseous, the most appropriate material will be the MTA.[49-11]

The clinical case report describes the treatment of a class 4 (Heithersay classification) external invasive cervical resorption in the left maxillary lateral incisor.

CASE REPORT

A 17-year-old female patient began an orthodontic treatment in a private practice a year ago. During maintenance consultations, the patient complained to the orthodontist of an increased sensitivity to cold stimulus in the left maxillary lateral incisor [Figure 1a]. The orthodontist observed a slight mobility in this tooth and the radiographic examination found a radiolucent area in the cervical portion of the lateral incisor root. With the likely diagnosis of an internal resorption, the patient was referred to an endodontist for evaluation.

Figure 1

Clinical (a) and radiograph (b) view of the anterior teeth. Cone beam CT revealing the external invasive cervical resorption - axial (c) and sagittal views (d). Intra-canal calcium hydroxide therapy of the maxillary left lateral incisor (e). After endodontic filling the restorative procedure was performed by using a fiber-glass intra-canal post (f), Surgical access of the maxillary incisor showing the identifi cation of the cervical resorption defect (g, h). Glass ionomer cement was carefully placed on the resorption area (i). Buccal (j) and palatal (k) view of the lateral incisor at eighteen months shows evidence of gingival healing. Periapical radiograph at 19 months follow-up showing no periapical changes (l)

During the clinical examination, the endodontist found that the mesial gingival papilla was slightly swollen and that the tooth was mobile. During the thermal sensitivity test, the patient reported pain symptoms to severe cold which persisted after the removal of the stimulus. There was sensitivity to percussion and a radiographic area of thickening of the apical ligament which could be attributed to the application of orthodontic forces. However, there was no tenderness. The same radiograph demonstrated an area of bone rarefaction at the mesial bone crest, but the periodontal probing did not show probing depth or gingival bleeding [Figure 1b].

Urgent treatment

Although the image suggests an internal resorption, clinically, there was only a slight edema in the adjacent proximal periodontium and sensibility pulp to the cold test which would involve an external resorption. As the pain persisted, an endodontic therapy was indicated as an emergency procedure. Because there was a marked structural loss in the tooth in the resorption lacunae and an endodontic access would cause more weakening, the best option was to install a bonded retainer at the level of cingulum with an orthodontic wire (0.7 mm in diameter) fixed in the adjacent teeth with composite resin (Four Seasons, Ivoclar Vivadent, Schaan, Liechtenstein). Thus, the removal of the pulp tissue was performed only with the use of small-diameter endodontic files with sodium hypochlorite (2.5%). An intra-canal medication with calcium hydroxide was introduced that would not produce artifacts in a cone beam computerized tomography (CBCT) image as one was needed to determine the extent of the resorption cavity and the treatment.

The diagnosis was confirmed on the CBCT image [Figures 1c,1d]. In the axial slices we could observe the entry points of the granulomatous tissue which were located in the mesial region at the bone crest. There was no communication with the root canal. The canal was not obvious because it was filled with calcium hydroxide medication. In fact, it was observed that there was an overflow of the medication in the resorptive defect.

The transversal image helped to make the clinical classification of invasive cervical resorption class 4 (Heithersay classification). Although, there was no communication with the root canal, the invasive resorption process was extending into the cervical and middle third of the root.

Since there was no communication between the resorption lacunae and the root canal as evidenced by the confinement of the medication to the intra-canal areas, the endodontic treatment was performed without increasing the root canal because it was already large and in need of a predominantly chemical preparation. The endodontic therapy was performed in two sessions, with an interval of two weeks, using a paste of calcium hydroxide as the intra-canal medication (Callen PMCC, SSWhite, Rio de Janeiro, Brasil) [Figure 1e]. After this period, it was carried a canal filling using gutta-percha and sealers (Endofill, Dentsply Maillefer, Rio de Janeiro, Brasil) with lateral condensation. At the following session, the restorative procedure was performed by placing a fiber-glass intra-canal retainer (White Post DC, FGM Produtos Odontológicos, Joinville, Brasil) [Figure 1f]. The restoration was carried out with a light-cured composite resin (Four Seasons, Ivoclar Vivadent, Schaan, Liechtenstein).

Periodontal surgery

The root canal therapy and tooth restoration were performed prior to repairing the external resorption defect because the proximity of the canal and the extensive loss of tooth structure could cause complications in periodontal surgery including dental fractures in the area.

After restoration, the next step in the treatment was the exposure of the resorptive defect through periodontal surgery. Initially, the local anesthesia was administered in the maxillary region and intrasulcular incisions were made on the buccal and palatal regions involving the adjacent lateral incisor. The mucoperiosteal flaps were spread which allowed the visualization of the entry point of the granulomatous tissue located in the cervical third of the root in its mesial aspect [Figure 1g].

As recommended by some authors,[35] the debridement of the resorptive defect was performed with a sonic instrument (Sonic Borden 2000N, KaVo Dental GmgH, Warthausen, Germany). The probing of the resorption lacunae showed hardened walls and the knife-edge cavity-shaped physical characteristics of invasive cervical resorption [Figure 1h]. Then we decided to restore the cavity with the restorative glass ionomer cement (Merion, Voco GmbH, Cuxhaven, Germany) because the location of the resorption was supra and subgingival. We used a centrix syringe (Centrix Inc., Shelton, Connecticut, EUA) to inject the cement. The objective was to fill the gap in the defect through a small hole in the access cavity [Figure 1i]. After the cavity was sealed, the gingival flap could be repositioned and sutured. The patient was instructed on oral hygiene practices including mouthwash twice a day with chlorhexidine solution 0.12% and was prescribed antibiotic therapy with amoxicillin 500 mg and potassium clavulanate combined, twice a day, for seven days. One week after the surgery, the suture was removed and the lesion was controlled.

Follow-up

After 19 months, the tooth remained asymptomatic and clinically showed a normal periodontal probing depth without any recession [Figures 1j,1k]. In the X-ray, we observed some radio-density showing a remodeling of the mesial bone crest [Figure 1l]. There was no tooth mobility.

DISCUSSION

Patients exposed to situations that can damage the support for the periodontal tissue such as orthodontic treatment in this case need to have careful periodic clinical examinations including X-rays.[112] Heithersay[5] found that orthodontic treatment alone was a predisposing factor in 24.1% of teeth with EICR.

Invasive cervical resorption is difficult to diagnose and it is even more challenging to identify the extent and nature of the process, especially in cases where the resorptive defect is buccal or palatine in location. With conventional radiographic images, there are limitations that not only prevent the proper identification of the resorptive process, but also hinder the planning and the evaluation of the prognosis with a treatment. Cone beam computerized tomography is imperative to reveal the extent of the defect in the differential diagnosis between internal and external resorption, especially whether the resorption lacuna is located above or below the bone and whether there is surgical access. All of these factors are relevant in the prognosis after treatment.[2] The images of the cone beam CT should include tangent (M / D), axial (more than 3 levels) and transverse (V/L) visualizations. In this case, the radiographic image suggested a class 3 ICR while the cone beam tomography showed a class 4 ICR including the entry point of the granulation tissue in the axial view.

The clinical classification of the external invasive cervical resorption proposed by Heithersay is effective for determining the appropriate treatment based on the extent of the resorptive defect. However, it is based on the radiographic image and it is tomography that reveals the true extent and severity of the injury.

Patel and Dawood[13] report on a clinical case where the image of the scan revealed that the defect presented by the ICR was longer (class 4) than what was determined using a conventional radiographic image. Therefore, the case was not treated because the scan image prevented the patient from having to undergo an unnecessary exploratory surgery. Heithersay[7] advocated that the selection of the case must be done carefully to achieve a favorable prognosis and recommended only treating defects that were class 1 to 3. Although our case was class 4, the maintenance of the dental element would have been appropriate, because as a teenager, the patient would have had potential facial growth that would prohibit the option of dental implants. In addition, the tooth loss would generate psychological problems in the patient.

The difficulty of the treatment was based on the possibility of periodontal aesthetic problems and the possibility of crown fracture. The solution was conservative periodontal surgery and placement of a post-core.

The axial image in the cone beam CT showed the proximity of the resorption lacuna with the root canal and the loss of extensive tooth structure which could cause complications subsequent to the treatment. Even the physiological masticatory movements could become a trigger of tooth fracture. Based on all these considerations, the post-core technique was used to provide a transfixation of the dental crown to the root portion that was not compromised.

The ideal characteristic of the root canal lumen for the insertion of a post is the presence of the canal walls. However, as found in this clinical case, the ability to insert the post involved the possibility of building the compromised root structure. Due to the mechanical properties of the post being comparable to tooth structure (especially its modulus of elasticity that is similar to dentin), the post would allow better stress distribution to the remaining teeth.[14]

A glass or quartz-fiber post system has a modulus of elasticity that is close to the remaining tooth and helps to distribute the stress on the tooth structure more uniformly in order to protect the root of the dental fractures.[15] Such improved retention is indicated especially for large canals, elliptical canals or iatrogenically-weakened canals, because they favor the juxtaposition of the post in relation to the root canal walls.[16]

It is believed that with the monoblock restoration system (i.e., a single biomechanical complex) the adhesion between the heterogeneous structures (remaining tooth, luting agent, post and filling material) in the remaining tooth structure would be improved, especially with the use of materials with physical properties similar to the dentin.[1617] It is important to note that at the time of debridement of the resorption, if a lacuna were observed there would be persistent bleeding coming from the defect. Thus, it implies that there is another point of vascular supply which would maintain the resorptive activity.[12]

CONCLUSIONS

The treatment of the external invasive cervical resorption of the lateral incisor interrupted the resorptive process and restored the damaged root surface and the dental functions without any esthetic sequelae.