Surgical Management of Invasive External Cervical Root Resorption Aided by Cone-Beam Computed Tomography: A CASE REPORT

INTRODUCTION
The clinical presentation of invasive external cervical root resorption (IECR) varies considerably and usually involves painless destruction of tooth structure that can often go unnoticed by patients and clinicians alike. While some teeth with highly vascular granulation tissue within the resorptive lesion may produce a noticeable pink spot in the cervical region of the tooth,1 others give no visual signs of pathosis. IECR can develop anywhere around the cervical area of the tooth and the patient is likely to remain asymptomatic until the lesion penetrates deep into the tooth structure. Heithersay2 introduced a classification based on the extent of the invasive resorptive lesion within the tooth: class 1, a small lesion near the cervical area with shallow penetration into dentin; class 2, a well defined lesion that has penetrated close to the coronal pulp chamber but shows little or no extension into radicular dentin; class 3, a lesion extending into the root to at least the coronal third; and class 4, a large lesion extending beyond the coronal third of the root canal. Injury to non-mineralized tissues covering the external surface of the root from dental trauma, mechanical, chemical irritation or surgical procedures can initiate a resorptive process which, without further stimulation may arrest spontaneously.3 A continued resorptive process results from a sustained stimulation and activation of osteoclasts through the OPG-RANKL-RANK system.4

The principal management options for IECR include no treatment, forced eruption, surgical access, and intentional replantation.5,6

The following case report describes the surgical restorative management of a class 3 IECR combined with an endodontic infection in tooth #1.1 that was previously root filled. Surgical management of IECR usually involves periodontal flap reflection, curettage and restoration of the defect followed by repositioning of the flap to its original position.6

CASE REPORT
A 59 year-old Caucasian male was seen for endodontic examination of tooth #1.1 that was previously treated but currently associated with discomfort. The patient also desired to improve the aesthetics of this tooth. The patient’s anamnesis revealed a non-contributory medical history. A review of the patient’s dental history revealed that some 20 years ago tooth #1.1 sustained a traumatic injury from a hockey puck and was subsequently treated.

The intra-oral examination (Figs. 1A & B) revealed that tooth #1.1 was restored with a porcelain-fused-to-metal crown with the margin exposed. The adjacent teeth had no restorations other than a lingual filling in tooth #1.2. Tooth #1.1 had a longer clinical crown compared to tooth #2.1. The gingiva appeared normal but there was tenderness to palpation at the palatal gingival margin of tooth #1.1, where the probing was 5 mm deep and caused profuse bleeding. At this site, irregularities on the root surface could also be probed.

FIGURES 1A. & B. Pre-operative intra-oral photograph.

FIGURE 1A.

FIGURE 1B.

Radiographic examination disclosed root fillings in teeth #1.1 and #1.2. In tooth #1.1, a radiolucent defect was localized below the cemento-enamel junction around the root filling (Fig 2). A periapical radiolucency was also present at tooth #1.1 with suggestion of apical external root resorption.

FIGURE 2. Pre-operative radiograph.

The patient was referred for small field-of-view cone-beam computed tomography (CBCT) imaging of the maxillary anterior region, to render three-dimensional images capable of disclosing the position of the resorptive defect, including its depth in relation to the root canal and apical extension; this information is helpful for determination of the intervention and the restorability. A diagnosis of a class 3 invasive cervical resorption6 combined with a periapical diagnosis of asymptomatic apical periodontitis was established (Figs. 3A & 3B).

FIGURE 3A. CBCT sagittal view. The resorptive defect is indicated by the arrow.

FIGURE 3B. 3D reconstruction of the defect opening on the palatal aspect.

Surgical and nonsurgical treatment options were presented to the patient, in addition to the possibility to extract the tooth and to replace it by an implant-supported crown. The risks and benefits of a nonsurgical approach were discussed, with the major drawback being an inability to trace the resorptive tissue to the external point of entry and completely eliminate this tissue.  A surgical approach would allow for complete removal of resorptive tissue and placement of restorative margins on sound tooth structure but would necessitate removal of alveolar bone, which could compromise the hard tissue support. The patient opted to have the resorptive defect restored through a surgical procedure, and provided informed consent for this approach.

Patient was asked to take 400 mg of Ibuprofen per os. Local anesthesia consisted of buccal and palatal infiltration of 3.4 ml of two percent lidocaine with 1:100000 epinephrine and palatal infiltration of 0.8 ml of two percent lidocaine with 1:50000 epinephrine to promote hemostasis. The patient was asked to use 0.12 percent chlorhexidine gluconate mouth rinse for one minute before the surgery. A palatal intra-sulcular incision was made from the mesial surface of tooth #1.4 to the mesial surface of tooth #2.3. An envelope full-thickness mucoperiosteal flap was elevated and secured with a silk ligature fastened around the contralateral molar #2.6 (Fig. 4). The granulation tissue was thoroughly curetted and the site irrigated with sterile saline. The resorptive lesion margins were found to be hard. Crestal bone was tri
mmed back to reveal a collar of sound tooth structure, which would facilitate finishing and polishing of the restoration and also provide an adequate biological width. The resorptive defect was cleaned with a #4 round bur at slow speed. The internal surface of the defect was recontoured and roughened with a diamond bur to make it more retentive (Fig. 5).

FIGURE 4. Palatal full thickness mucoperiosteal flap secured with a silk ligature fastened to a contralateral molar.

FIGURE 5. IECR defect after debride­ment.

Bleeding was controlled with ferric sulfate (Astringedent; Ultradent Products, Inc., UT) and the surface cavity rinsed clean with sterile saline then dried with sterile cotton pellets. Tenure Multi-Purpose Bonding System (Den-Mat Corporation, Santa Maria, CA), a multi-purpose bonding system, was applied with a micro-applicator for 15 seconds, gently dried with pressured air for 10 seconds and light-cured for 30 seconds. Geristore (Den-Mat Corporation) was dispensed with the auto-mix syringe into the prepared cavity, lightly condensed to adapt the margins and light-cured for 40 seconds. The restoration was then contoured in both an occluso-apical and mesio-distal planes and finished with 12 and 30 fluted finishing burs (Fig. 6).

FIGURE 6. IECR repaired with Geristore.

The flap was repositioned to cover the coronal margin of the restoration and secured with 4-0 plain gut (Hu-Friedy, Chicago, IL) interrupted sutures. A post-operative radiograph was exposed (Fig. 7). The patient was prescribed Ibuprofen 600mg q.i.d. pro re nata to mitigate postoperative discomfort. He also was instructed to use 0.12 percent chlorhexidine gluconate mouth rinse for seven days to curtail intraoral microbes during the healing period.7

FIGURE 7. Post-operative x-ray after surgical repair of IECR.

Six days after the surgery gingival healing appeared satisfactory. The palatal gingival tissue was less tender to palpation than pre-operatively.

Three weeks after the surgical intervention, orthograde root canal re-treatment was performed under operative microscope (Pico; Zeiss, Oberkochen, Germany). The crown was gently removed with a Morrel crown remover (Miltex, Plainsboro, New Jersey) and kept to serve as a temporary restoration. After rubber dam isolation and surface disinfection with 2.6 percent NaOCl, the root canal was accessed, the coronal 3 mm of root filling material removed with Gates-Glidden drill #3 and chloroform dripped into the space created. The working length was established with the aid of an electronic apex locator (Root ZX; J. Morita Co. Suita City, Osaka, Japan). Once a glide path was achieved with a hand K-type file (Dentsply Maillefer, Ballaigues, Switzerland), a WaveOne Primary instrument (Dentsply Maillefer) was used in reciprocating motion to remove the remaining softened gutta-percha. Under high magnification, particular care was taken for the debridement of the lingual portion of the root canal to the extent that no irregularities were seen or felt on the root canal walls when explored with a #10 pre-curved stainless steel K-file. Complete removal of the previous root canal filling material was confirmed visually through the operative microscope and with an intraoral radiograph. The canal was enlarged to a #45 master apical file and irrigated with 2.6 percent NaOCl throughout the procedure, Final irrigation was performed with 17 percent EDTA to remove smear layer, followed by 2.6 perent NaOCl delivered using the EndoVac system (SybronEndo, Orange, CA). The canal was dried with paper points and filled with vertically-compacted warm gutta-percha and Thermaseal sealer (Dentsply Tulsa Dental, Tulsa, OK). A layer of resin-modified glass-ionomer cement (Vitrebond; 3MESPE, St. Paul, MN) was applied at the canal orifice just below the cervical level and the access cavity restored with glass-ionomer cement (Fuji-II, GC Corp., Tokyo, Japan) (Fig. 8). The original crown was temporarily cemented with TempBond (Kerr Corp., Orange, CA) (Fig. 9).

FIGURE 8. Final x-ray after orthograde root canal re-treatment.

FIGURE 9. Palatal soft tissue appearance one month post IECR surgical repair.

The patient is currently undergoing treatment to replace the inadequate crown on tooth #1.1. He is scheduled for routine follow-up examinations to assess the outcome of treatment in the long-term.

DISCUSSION
This case report illustrates the management of a late complication of a traumatic injury that occurred some 20 years before. While the persistent root canal system infection, resulting in chronic apical periodontitis, could develop independently of the external root resorption, it could not be properly treated in the presence of the cervical communication with the oral environment. The treatment plan, therefore, required the latter to be effectively sealed before the former could be addressed with adequate aseptic approach. Although the patient’s pre-operative symptoms completely disappeared short
ly after treatment, further follow-up is mandatory to confirm the long-term outcome of treatment in regards to periapical healing but also periodontal healing and absence of recurrent resorption.

Interestingly, the external resorption defect was rather large when intercepted despite the patient’s diligent visits to the dentist. The absence of a vital pulp and the difficulty to identify the resorptive defect on an intraoral radiograph due to its palatal location may have partially accounted for this late diagnosis.

Early IECR lesions are difficult to detect in routine dental examinations.6 While localized gingival inflammation may occur early on in the disease process, a corresponding radiographic radiolucency can only be detected at this stage if the location is specifically mesial or distal. As the resorption penetrates further into the dentin, the radiolucency increases in size and a pink discoloration of the tooth crown often appears.6 Sensibility testing usually yields normal responses suggesting a vital non-inflamed pulp.9 Radiographically, an irregular mottled, or “moth–eaten” area appears that, when approximating the root canal, is demarcated from it by a distinct radiopaque line representing the predentin, which appears to protect the pulp.10 Class 1, 2 and 3 lesions are often asymptomatic unless there is a secondary pulpal or periodontal infection. The more advanced Class 4 lesions extend beyond the coronal third of the root and are more readily characterized radiographically by extensive radiolucent defects. In these advanced stages, the predentin demarcating the pulp from the resorptive lesion may be lost.2

Intraoral radiographs rarely indicate the true dimensions of IECR defects. The loss of tooth structure, which can spread within the root in all directions, cannot be adequately reflected in a two dimensional image.11 The advent of three-dimensional radiography provides previously unavailable tools to facilitate interactive image manipulation, enhancement and reconstruction of hard tissues from alternate views.12 Several case series and reports have demonstrated the benefits of CBCT in the diagnosis and management of resorptive lesions.13-15 In the case presented here the CBCT analysis not only helped confirm the diagnosis, but also provided valuable information regarding the remaining tooth structure and aided in planning the surgical approach.

The resorptive defect was sealed from the oral cavity with Geristore, a hydrophilic, nonaqueous polyacid-modified composite resin. It is considered suitable for treating subgingival defects because of its insolubility in oral fluids, high adhesion to dentin, dual-cure capabilities, low shrinkage, fluoride release and compatibility with human periodontal cells.16,17 It also is relatively easy to manipulate and can be polished to produce a smooth surface. In addition to its favorable attributes, periodontal attachment to Geristore surface may occur.17,18

In this case, a surgical approach was selected from several alternative options, to gain access to and to seal the resorptive defect. The main drawbacks of this approach are two-fold: 1. The surgical environment is hardly optimal for effective conditioning of dentin and bonding of the restorative material to the defect wall, possibly resulting in compromised restorations; 2. The pre-operative bone loss combined with additional crestal bone removal at the site of the resorptive defect can compromise the alveolar bone crest architecture, which is not conducive to long-term stability and health of the periodontal tissues.19 The unfavorable periodontal condition is further aggravated if insufficient biological width is established during the procedure in an attempt to conserve bone.20,21

Heithersay22 described a non-surgical approach to the management of IECR involving the topical application of a 90 percent aqueous solution of trichloracetic acid (TCA) to the resorptive tissue, with subsequent curettage, endodontic treatment where necessary, and restoration with glass-ionomer cement.6,22 This procedure critically depends on TCA cauterizing all resorptive tissue; if not all penetration points are exposed, resorption may reoccur.9

Another alternative in the management of IECR is orthodontic forced extrusion of the affected tooth.23 By rapid movement of the tooth coronally, access to the IECR defect is facilitated, enabling better control of the restorative procedure and, importantly, preservation of favorable bone crest architecture.23,24 The main drawbacks of this approach, however, are the length of time required to extrude the tooth and the high associated cost.23

In cases of IECR where the resorptive portal of entry is inaccessible by conventional surgical approaches, or where the defect is widely open to the outer surface, intentional replantation can be considered as a last resort, essentially as an attempted alternative to extraction and prosthetic replacement of the affected tooth.25 This approach involves extraction of the tooth, keeping it constantly moist, extraoral debridement and restoration of the defect, and replantation of the tooth into the socket within the shortest time possible but no more than 20 minutes.26 The tooth is splinted with a non-rigid splint for a period of one to two weeks.27 Endodontic treatment is performed after two weeks, when the tooth has become stable enough.28,29 The main risk of this procedure is fracture of the tooth upon the attempt to extract it.25

CONCLUSION
This case report describes the surgical management of a root-filled maxillary incisor with persistent apical periodontitis and extensive IECR where diagnosis and treatment planning were assisted by CBCT imaging. Management included a surgical access, osteotomy and sealing of the resorptive defect with Geristore, followed by orthograde retreatment. Two months after treatment, the patient was asymptomatic. Further follow-up is required to confirm the long-term outcome of treatment. Current technology and materials make the retention of teeth affected by IECR a realistic and valuable option. OH

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Dr. Karine Charara received her DMD degree from the Faculty of Dentistry at the University of Montréal in 2009. She is currently a second year Graduate Endodontic resident at the University of Toronto and a faculty member at the Faculty of Dentistry of the Université de Montréal.

Dr. Andrei Ionescu received his DMD degree from the Faculty of Dentistry at the University of British Columbia in 2008. He completed a general practice residency at St. Barnabas Hospital in New York and is currently a second year Graduate Endodontic resident at the University of Toronto.

Dr. Jason Gagliardi earned his MSc from the University of Western Ontario in 2006 and received his dental training at the University of Toronto in 2011. He is currently a second year Graduate Endodontic resident at the University of Toronto.

Oral Health welcomes this original article.

Acknowledgment
The authors would like to thank Dr. Shimon Friedman, Dr. Calvin Torneck and Dr. Bettina Basrani for their insights into the article and Dr. Shaul Dwosh for his surgical assistance on the case.

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