Table of Contents  
CASE REPORT
Year : 2017  |  Volume : 9  |  Issue : 1  |  Page : 58-62

Use of cone-beam computed tomography in diagnosing and treating endodontic treatment failure: A case study


1 College of Dental Medicine, Columbia University, New York, NY, USA
2 Department of Diagnostic Sciences, Division of Oral and Maxillofacial Radiology, Rutgers School of Dental Medicine, Newark, NJ, USA

Date of Web Publication14-Jun-2017

Correspondence Address:
Gloria Lee
1324 Locust St. Apt 614, Philadelphia, PA 19107
USA
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0975-8844.207950

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  Abstract 


The use of cone-beam computed tomography (CBCT) as a complementary imaging modality applies to various clinical situations that with conventional two-dimensional radiographs alone may pose diagnostic challenges. These challenges include but are not limited to locating missed canals in endodontic retreatment and diagnosing the presence of lesions such as resorption, periapical bone defects, root fractures, and perforations. In this study, we present a case of an asymptomatic apical periodontitis that was incidentally found on a panoramic radiograph. Analyses based on panoramic and periapical radiographs and clinical examinations were insufficient for definitive diagnosis, which necessitated the use of CBCT. The CBCT scan allowed identification of the cause of the apical disease, an unfilled mesiolingual canal in previously root canal treated left mandibular second molar, as well as the extent of the lesion. We also explore the diagnostic challenges in using traditional two-dimensional radiographs only, the challenges in locating root canals in mandibular second molars, and risks and benefits in using CBCT.

Keywords: Cone-beam computed tomography, differential diagnosis, endodontic treatment failure


How to cite this article:
Lee G, Lankalis J, Tamari K, Singer SR. Use of cone-beam computed tomography in diagnosing and treating endodontic treatment failure: A case study. J Orofac Sci 2017;9:58-62

How to cite this URL:
Lee G, Lankalis J, Tamari K, Singer SR. Use of cone-beam computed tomography in diagnosing and treating endodontic treatment failure: A case study. J Orofac Sci [serial online] 2017 [cited 2023 Jan 31];9:58-62. Available from: https://www.jofs.in/text.asp?2017/9/1/58/207950




  Introduction Top


The use of cone-beam computed tomography (CBCT) is indicated in various dental diagnoses and treatments for lesions that require three-dimensional evaluation for accurate assessment, particularly given the limited diagnostic information provided by conventional periapical radiographs. The use of CBCT, however, “should be prescribed only after weighing the risks of radiation exposure with the benefit of the diagnostic information that can be obtained from the scan,”[1] according to the American Association of Endodontists and the American Academy of Oral and Maxillofacial Radiology.

Identification and proper obturation of all root canals provide significant challenges to clinicians performing endodontic therapy. Historically, dentists have relied on two-dimensional periapical radiographs to determine relevant root structure, anatomy, and progress of treatment. Since 2001, when the first CBCT unit was approved by the Food and Drug Administration for dental use in the United States,[2] there has been an increase in its use as a complementary modality to traditional radiographs.

One of the most difficult aspects of providing appropriate endodontic therapy is the proper identification of all canals present. Although root morphology has been documented extensively,[3],[4] the identification of root anatomy for a particular patient can still present a challenge clinically as there can be extensive variation between patients. Improper identification of all relevant anatomy can lead to predictable failure of treatment. Thus, the use of diagnostic imaging is critical to provide adequate therapy.

Although untreated anatomy has been documented as a significant cause of endodontic failure, the imaging in this case graphically illustrates the untreated mesiolingual canal and the resultant apical inflammatory lesion.

Two-dimensional periapical films have been the standard diagnostic imaging modality used for determining both root structure and extent of any apical periodontitis present. However, the conventional periapical radiograph has several limitations that can lead to undetected pathology or improper treatment. Conventional radiographs are also limited in that they provide a two-dimensional image of a three-dimensional structure. The compression of the third dimension in the image may obscure significant anatomy or pathologic changes.[5] Second, while standard two-dimensional radiograph's ability to resolve changes in bone relies on a percentage change in calcification, lesions in the cortical bone are detected radiographically only when perforation of the bone cortex, erosion of inner surface of bone cortex, or significant defect on the outer surface exists. In fact, periapical lesions in cancellous bone are often not detected radiographically.[6]

CBCT is an essential diagnostic imaging modality among current radiographic methods. Its ability to detect root canals preoperatively is significantly greater than that of conventional two-dimensional films,[7] thus providing valuable diagnostic information leading to proper treatment planning, such as endodontic retreatment. In addition, CBCT showed significantly greater ability to periapical lesions ex vivo when compared to conventional films.[8] More importantly, CBCT was able to detect, on average, 0.88 more canals per tooth on previously root filled.[9]

The findings are explained by the major advantage of CBCT over conventional two-dimensional radiographs. The two axes compressed superimposition of radiodense structures may obstruct viewing of radiolucent lesions. CBCT allows for viewing three-dimensional structures in using multiplanar reconstruction in sagittal, axial, and coronal views as well as oblique views. This often allows otherwise occult lesions to be visualized. CBCT, by allowing visualization of anatomy in variable planes, permits the anatomy of canals to be visualized. For example, buccal position of one canal within a root may suggest the presence of the second canal as in mesiobuccal canal in maxillary molar. Disadvantages of CBCT include costs, radiation, lower resolution, and artifacts from radiopaque structures including restoration and existing root canal materials.

Mandibular second molars show greater variation in anatomy within the population due to different configurations of the mesial and distal roots. Seventy-six percent of second molars are two-rooted, 22% are one-rooted, and 2% were three-rooted.[10] The root configuration of mesial root has a fairly even distribution between a single canal in 27% of cases, two fused canals 38%, and two anatomically distinct canals 35%. The distal root has much less variation – a single canal in 92%, two fused canals in 3%, and two distinct canals in 5%. In addition, lateral canals were found in 49% of mesial roots and 34% of distal roots.[4]

The contemporary rate of endodontic failure is approximately 8% after 2 years [11] for canals that have been treated to clinically acceptable standards, such that all canals have been adequately identified, instrumented, and obturated with proper coronal restoration and seal. The success rate drops significantly to 40%–50%, but when the tooth has not been treated to acceptable standard.[12] Of cases in which endodontic retreatment is necessary, however, only 3% are due to unfilled canals. Instead, the overwhelming majority is due to incomplete obturation.[3] Worth noting is that certain studies have identified missed canals present in 42% of endodontic failure cases [11] even though they were not necessarily the cause for failure. This suggests the possibility that canals are missed because of operator error, either in obtaining a good image or in identifying anatomy in an image, and indicates the need for a better method of visualizing root anatomy. Several studies have found that endodontists and oral and maxillofacial radiologists may identify as low as 76% as many canals on traditional radiographs, but up to 100% of canals on CBCT radiographs.[9],[13] This clearly shows that for patients for whom the additional radiation exposure is deemed beneficial, CBCT is a far superior diagnostic imaging modality than conventional two-dimensional radiographs.


  Case Report Top


A 31-year-old female patient presented to the clinic for emergency dental treatment. Her chief complaint for the emergency visit was pain associated with right mandibular third molar, tooth 32. The patient reported that her filling had fractured 2 weeks before the visit and reported that the pain was associated with mastication, sweets consumption, and hot and cold temperature. The night before visit, the patient was unable to sleep due to constant pain.

Clinical extraoral examination failed to reveal swelling, and no cervical or submandibular lymphadenopathy was noted. Intraorally, noncontributory findings included multiple existing restorations, fractured restoration, and periodontal probing depths of 4 mm in left mandibular second and third molars, teeth 17 and 18.

A panoramic radiograph was prescribed and exposed. Radiographic findings included complete and erupted permanent dentition, as well as root canal-treated teeth. Carious lesions were noted, including tooth 18. Periodontal bone appeared to be within normal limits. An incidental radiographic finding of periapical radiolucency in the apical areas of left mandibular first and second molars, teeth 18 and 19, encroaching the left mandibular canal was noted [Figure 1].
Figure 1: Panoramic radiograph demonstrated incidental finding of the periapical radiolucency involving apices of left mandibular first and second molars (teeth 18 and 19)

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In addition to providing care to patient's chief complaint, pain in tooth 32, steps were taken for further evaluation of the periapical lesion in the left mandible. Clinical examination revealed that tooth 18 was slightly positive to percussion, tooth 17 mildly sensitive to percussion, and teeth 19–21 not sensitive to percussion. No tenderness to palpation in left mandible was observed, and the patient has had no symptoms associated with the lesion in the area of interest. No teeth in the left mandible exhibited mobility. When tested for vitality with Endo Ice ® Refrigerant Spray (Coltene Whaledent, Cuyahoga Falls, USA), all premolars and molars except tooth 18, previously root canal treated, in the left mandible showed positive response to cold for 1–4 s with no lingering sensitivity, indicating their vitality. There were no pocket depths >3 mm in posterior teeth in left mandible with the exception of depths of 4 mm in teeth 17 and 18. A periapical intraoral radiograph was obtained in the area of interest, which revealed a corticated radiolucency between teeth 18 and 19 extending posteriorly and inferiorly toward the mandibular canal.

The patient reported that the endodontic therapy was performed in tooth 18 approximately 5 years ago. Prior radiographs were not available. The patient reported that she had experienced no complications after receiving the treatment.

Based on the radiographic appearance and position of lesion superior to mandibular canal, the lesion was presumed to be of odontogenic etiology or origin. Due to the position of the lesion in relation to teeth and proximity to mandibular canal, CBCT examination of mandible was prescribed and exposed. The CBCT scan revealed a well-demarcated hypodense lesion with epicenter at apices of tooth 18, extending to distal root of tooth 19, posteriorly to interdental bone between teeth 17 and 18. The size of the lesion was 25 mm mesiodistally, 11 mm vertically, and 10 mm buccolingually. The lesion extended into the furcation of tooth 18, its superior border was within 2 mm of superior crest of bone, both buccal and lingual cortices were thinned, and the buccal plate was perforated due to the extent of the lesion. The inferior and posterior portion of lesion was in proximity to superior cortex of left mandibular canal, and confluence of lesion with the canal could not be excluded. In addition, the distal surface of mesial root of tooth 18 appeared thinned and perforation could not be excluded.

An axial view at mid-root level [Figure 2] demonstrated the presence of an unfilled mesiolingual canal in tooth 18. A coronal view of mesial root of tooth 18 [Figure 3] demonstrated the buccal position of the filled canal and the presence of the unfilled lingual one as well as perforation through the bucc

al plate due to the lesion. A sagittal view from CBCT scan [Figure 4] demonstrated the lesion extending within 2 mm of superior crest of bone and encroaching the superior cortex of left mandibular canal. The gutta-percha close to distal wall of mesial root in tooth 18 seen in this view was not seen in two-dimensional periapical radiograph. Another coronal view of CBCT scan captured with tooth 17, distal to tooth 18, demonstrated confluence of lesion with the left mandibular canal.
Figure 2: Axial view at mid-root level shows an unfilled mesiolingual canal in tooth 18

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Figure 3: Coronal view of mesial root of tooth 18. The buccal position of the filled canal, the presence of the unfilled lingual canal, and perforation through the buccal plate due to the lesion are revealed

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Figure 4: Sagittal view shows the lesion extending within 2 mm of superior crest of bone and encroaching the superior cortex of left mandibular canal

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Differential diagnosis of the lesion included an apical inflammatory lesion associated with nonvital tooth 18. Less likely, diagnoses included simple bone cyst, central giant cell lesion, and ameloblastoma. Based on the radiographic appearance, the presence of unfilled mesiolingual canal in tooth 18 indicated that the most likely differential diagnosis was an apical inflammatory lesion.

With the most likely differential diagnosis being endodontic failure due to unfilled mesiolingual canal in tooth 18, the patient was presented with two treatment options, endodontic retreatment versus extraction of tooth. Various clinical factors may indicate endodontic retreatment or indicate against it,[14] and in this case, as the patient had few clinical signs of infection, a coronal restoration that needed to be replaced due to open margins, and no previous history of failed endodontic retreatment, endodontic retreatment was suggested in preference over extraction. The patient desired endodontic retreatment and refused extraction. Thus, endodontic retreatment and restoration with coronal seal were prescribed for the lesion and radiographic follow-up was suggested. If the lesion does not show no resolution in subsequent radiographic follow-ups, a biopsy of the lesion would be performed, a goal standard for diagnosis of infrabony lesions. Follow-up radiographs are usually recommended not less than 6 months after the retreatment. The patient was also instructed to return with pain or expansion of bone in the area.

Following the emergency visit, the patient was followed up by an endodontist to complete endodontic retreatment with occlusal access through the existing coronal restoration. Then, the patient was followed up by a general dentist for the removal of existing defective coronal restoration, cementation of post and core, as well as crown.


  Discussion Top


Mandibular second molars exhibit high degrees of anatomic variability within the population. The mesial root has a nearly even distribution of single canal, two canals that are separate and two canals which are joined. While the distal root shows less variation in its anatomy, different canal structures are present in nearly 10% of the population and must be considered during treatment. Such variation requires clinical and didactic expertise on the part of practitioners performing endodontic therapy, which would contribute to success or failure of the endodontic treatment. Upon failure, accurate diagnosis identifying the cause of failure is essential in determining the treatment needed. When two-dimensional radiographs are not sufficient in obtaining such diagnosis, the use of CBCT is prescribed as it offers visibility in multiplanar views, enabling establishment of suitable treatment options.

Recent studies have shown the significant benefit of using CT [15] and CBCT [16] in diagnosing the cause of endodontic failure. These three-dimensional imaging modalities enable visualization of restoration materials, missed canals, root fractures, coronal seal, or any other etiological factor contributable to endodontic failure.[17] One study demonstrated that with CBCT more root canals were found when compared to periapical radiographs during presurgical planning for root apex surgical therapy.[7] Other studies demonstrated higher prevalence of periapical radiolucent lesions for endodontically treated teeth with the use of CBCT as the imaging modality over the use of periapical radiography.[9] This reinforces the role of CBCT as complementary imaging modality in obtaining accurate diagnosis when traditional two-dimensional radiographs do not provide sufficient information.

Initial radiographs of the patient showed that the lesion appeared to have spread within immediate proximity of the left mandibular canal. Although uncommon, cases of inferior alveolar nerve and mental nerve paresthesia due to apical infection have been reported in literature.[18] The CBCT scan revealed that the lesion had not completely effaced the superior cortex of the left mandibular canal. Yet, odontogenic periapical infections can cause paresthesia by pressure-induced ischemia even when there is no direct communication of the lesion with the nerve. As the patient had not yet developed any sign of paresthesia, discomfort, or numbness associated with the left side of her face, the incidental discovery of the periapical inflammatory lesion associated with endodontic failure of tooth 18 was crucial and in the best interest of the patient's health. While the CBCT scan demonstrated the extent of lesion, continued radiographic follow-up including patient observation and reporting is important in determining the presence of nerve damage.

Such follow-up is also important as the patient presented with a chronic underlying problem that was asymptomatic that could lead to flare-up postretreatment due to “inoculating irritants to the attachment apparatus during the removal of existing materials or during the preparation of the canal.”[19] To decrease the chance of a retreatment flare-up, some patients can be placed on antibiotic prophylaxis. With flare-up, microsurgery or extraction would be rendered given that the etiology of the lesion was odontogenic in origin, an unfilled mesiolingual canal.

The risks and benefits associated with the use of CBCT as an imaging modality for accurate diagnosis are first weighed before prescription and exposure. This is due to the concerns with radiation exposure and is the reason why CBCT is a complementary imaging modality to conventional two-dimensional radiographs. Yet, the amount of radiation from a single scan is less than that of a single panoramic radiograph on certain models and rarely does a CBCT scan expose patients with radiation significantly greater than background radiation.[20] The CBCT exposes patients to only a portion of radiation exposed through a medical CT and everyday environmental exposure and, therefore, puts patients at minimal radiation risks.[21] The amount of radiation a patient may be exposed during CBCT scan depends on several factors including the size of the field of view, whether image is taken in continuous or pulsed patterns, and the number of rotations around the area of interest the machine makes during the exposure.


  Conclusion Top


This case demonstrated the benefit of using CBCT to identify the cause of periapical radiolucent lesion and thus arrive at a definitive diagnosis of an inflammatory lesion secondary to endodontic treatment failure associated with an unfilled canal. Visualization of the tooth's three-dimensional anatomy is often not achievable using two-dimensional periapical and panoramic radiographs, patient report, and clinical examination. In the presented case, differential diagnoses for other etiology were excluded with the aid of CBCT. As demonstrated in this case, the use of CBCT as a complementary imaging modality applies to various clinical situations that with conventional two-dimensional radiographs alone may pose diagnostic challenges, including but not limited to location of calcified canals, diagnosing the presence of resorption lesions, periapical bone defects, root fractures, and perforations, and identification of missed canals in endodontic retreatment.[1] As 42% of missed or unfilled root canals lead to endodontic failure, the benefits of preoperative or diagnostic CBCT may be greater than the risk of minimal radiation exposure.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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