Root canal filling material in periapical lesions: A polarized and fluorescent light microscopy case series : Saudi Endodontic Journal

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Case Report

Root canal filling material in periapical lesions: A polarized and fluorescent light microscopy case series

da Silva, Cristiane Cantiga; Cintra, Luciano Tavares Angelo; Machado, Nathalia Evelyn da Silva; de Lima, Luis Armando Henrique1; de Almeida, Tatiane Matos1; Vieira, Ana Julia Desideri1; de Vasconcelos, Antonio Jorge Araujo II1; Ribeiro, Lidiane De Paula1,; Cabral, Lioney Nobre1; Pinheiro, Tiago Novaes1

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Saudi Endodontic Journal 13(2):p 197-203, May–Aug 2023. | DOI: 10.4103/sej.sej_188_22
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Abstract

INTRODUCTION

Endodontic treatment is completed through root canal filling with biocompatible materials, such as gutta-percha cones and root canal sealers.[1] The biocompatibility of materials is being thoroughly investigated in the field of dentistry. The properties of the filling materials, combined with biomechanical preparation and the patient’s immune response, are crucial factors for successful endodontic treatment.

The apical constriction of the root canal could be affected as a result of inflammatory resorption of the root apex or an incompletely developed root apex. Overfilling the root canals is a frequent complication and is related to overinstrumentation.[2,3] Despite being biocompatible, overfilled materials can act as a foreign body and cause irritation of the periapical tissues, leading to failure of the endodontic treatment[4] and severe postoperative complications[5] and persistent inflammation.[6]

Endodontic sealers should have adequate sealing capacity against microorganisms and their by-products,[7] in addition to good biocompatibility with periapical tissues in cases of overfilling, adequate solubility in the oral environment, radiopacity, and dimensional stability.[8] The fate of the filling material in the periapical tissues depends on its solubility in tissue fluids and susceptibility to phagocytosis, since it can be reabsorbed or encapsulated by fibrous connective tissues. The physical and chemical properties of the materials are responsible for the different tissue responses.[9] Gutta-percha is a solid material mostly used in filling the root canals. When extruded, it can be encapsulated, similar to some sealers that have epoxy resin as a component.[10]

Ricucci et al. showed that extravasation of the filling material can delay tissue repair and that its extrusion with a periapical lesion can lower the success rate of the endodontic treatment.[11] A case report by Bjørndal et al. showed complete extrusion of an obturator material into the maxillary sinus, causing clinical symptoms in the nose region with differential diagnostic aspects, which, in turn, prompted the need for several surgical treatments in the nostrils.[12] Complementary examinations, such as cone-beam computed tomography, were performed to locate the material more accurately. It was surgically removed and subsequently referred for analysis using scanning electron microscopy and transmission electron microscopy, which showed the formation of microbial biofilm without obturating material or remains of sinus mucosa.

Although many causes of endodontic failure related to overfilling of the material have been described in the literature,[13] only a few studies have used microscopic techniques to identify the type of filling material associated with the lesion and tissue changes.[14] This study reports two clinical cases of overfilling of the root canal associated with unsuccessful endodontic procedures. The aim of the study was to investigate the morphological properties of overfilling materials associated with periapical lesions by polarized and fluorescent light optical microscopy analysis.

CASE REPORTS

Case 1

A 36-year-old woman had a previous history of an unsatisfactory endodontic treatment attributed to overfilled material of tooth maxillary right first premolar (#14) verified by periapical radiograph [Figure 1a]. The patient complained of persistent pain for over 3 months after the endodontic treatment and, therefore, preferred the tooth to be extracted. However, she reported persistent pain in the premolar region of the right side of the maxilla after the extraction leading her to seek further attention. Her medical history was not relevant.

F1
Figure 1:
(a) Periapical radiograph showing an endodontic treatment in tooth #14 with overfilled root canal material. (b) Tomographic image showing a radiopaque region mixed with soft tissue. (c) Postoperative periapical radiograph revealing the persistence of the radiopaque root canal filling material. (d) Excision of the lesion for histopathological evaluation. (e) Postoperative radiograph confirming complete removal of the lesion. (f) One-week postoperative follow-up after suture removal

Clinically, the patient was sensitive to any contact in the region. The periapical radiograph showed a 4-mm wide radiopaque area in the apical region, suspected to be a residual filling material. The tomographic examination revealed that the radiopaque material was located under the oral mucosa, close to the maxillary bone, possibly due to an anterior bone fenestration that had already healed [Figure 1b and c]. The diagnostic hypothesis was foreign body granuloma.

An excisional biopsy was performed, and the excised soft tissue mixed with the endodontic filling material was submitted for histopathological evaluation [Figure 1d]. An additional postoperative periodical radiograph confirmed total removal of the lesion, without any residual foreign material [Figure 1e and f].

Microscopic evaluation of the specimen revealed loose, nonmodeled connective tissue, with a heterogeneous central blackish mass of foreign materials surrounded by giant foreign body cells and focal areas of intense lymphocytic inflammatory infiltrates with focal basophilic coagulative necrosis [Figure 2a and d]. The evaluation of samples under polarized and fluorescent light revealed birefringence of calcium hydroxide in the endodontic sealer and fluorescence of the gutta-percha with red and green fluorescent filters, respectively [Figure 2b and c]. The diagnosis was conclusive for foreign body granuloma owing to extrusion of gutta-percha and a calcium hydroxide-based sealer, which leaked into the submucosa.

F2
Figure 2:
(a) Hematoxylin and eosin staining of tissue revealing a foreign body with a heterogeneous appearance and the presence of giant cells and areas of lymphocytic inflammatory infiltration. (b) Polarized light microscopy showing birefringent calcium hydroxide particles in the endodontic sealer. (c) Fluorescent light using a green filter highlighting the fluorescent property of gutta-percha. (d) Microscopy at higher magnification showing foreign body giant cells (×640)

The postoperative period and healing trajectory were as expected, without complications [Figure 1f], and the patient reported a significant improvement in pain. As there was no bone lesion, follow-up was carried out by questioning the patient regarding pain and edema in the operated region for 3 consecutive weeks. The patient recovered completely during this follow-up period being released from treatment.

Case 2

A 35-year-old man with a 7-year history of facial trauma due to a traffic accident was referred to the oral medicine service. He reported discomfort when pressing the left nostril. He stated that the maxillary left lateral incisor (#22) was extracted following a previous unsatisfactory endodontic treatment for 4 years. His medical history was not relevant. Clinical examination showed painless nonmobile swelling of the superimposed region, which was bluish in color. Panoramic radiography revealed a radiolucent image with defined borders and a radiopaque spot within the radiolucent area [Figure 3a]. Computed tomography revealed a hypodense radiopaque spot in the region of the extracted tooth [Figure 3b]. In addition, three-dimensional reconstruction of the image showed a well-defined area of bone destruction between the maxillary left central incisor (#21) and the maxillary left canine (#23) [Figure 3c]. The diagnostic hypothesis was a residual cyst. An excisional biopsy of the lesion was performed and a foreign body was observed inside the cyst, along with the cystic content [Figure 3d-f].

F3
Figure 3:
(a) Panoramic radiograph showing a well-circumscribed radiolucent lesion with a radiopaque foreign body. (b) Computed tomography revealed a hypodense radiopaque spot in the region of the extracted tooth. (c) Three-dimensional image showing bone destruction between teeth #21 and #23. (d) Trans-surgical view of the lesion showing a foreign body inside the cystic content. (e) Excisional biopsy with enucleation of the lesion. (f) Gross appearance of the cyst

The histopathological analysis revealed a cystic cavity lined by stratified squamous epithelium, with blackened fragments mixed with the cystic content [Figure 4a]. Birefringent calcium hydroxide granules were observed under polarized light, and fluorescence pattern corresponding to that of gutta-percha was observed under fluorescent light [Figure 4b and c]. The diagnosis was conclusive for residual cyst.

F4
Figure 4:
(a) Hematoxylin and eosin staining of the cyst highlighting the thin lining of stratified epithelial cells, hemorrhagic content in the fibrous capsule, and a foreign body in the cystic cavity with basophilic dystrophic calcifications and an inflammatory serofibrinous exudate. (b) Polarized light microscopy of the mixed gutta-percha and calcium hydroxide-based sealer, highlighting birefringent particles of calcium hydroxide. (c) Fluorescent light microscopy using a green filter showing the serofibrinous exudate (red), gutta-percha (pink), and endodontic sealer (pink)

The patient was kept under periodical clinical follow-up, being released from treatment after 2 years presenting complete clinical recovery, without any symptoms confirmed by clinical and tomographic examinations. Furthermore, he already had started prosthodontic rehabilitation [Figure 5].

F5
Figure 5:
(a) Clinical examination revealing excellent recovery of the region. (b and c) Cone-beam examination and three-dimensional reconstruction revealing complete bone healing at the treated site

DISCUSSION

The success rate of endodontic treatments ranges from 86% to 98%.[15] Even in teeth with periapical lesions, the success rate is high, at approximately 94%, when root canal filling remains within the range of 0–2 mm from the apex.[16] Tabassum and Khan reported in a recent literature review that causes of endodontic treatment failure remain largely unchanged through the course of the time with emphasis on the persistence of intra- and extra-radicular microorganisms, inadequate filling of the root canals, and overextension of root filling materials.[17] When evaluating teeth with endodontic failures, it was observed that 65% of cases exhibited low-quality obturation.[18] In addition, overfilling canal was a factor in endodontic treatment failure nearly four times higher than canals filled short of the radiograph foramen,[19] which could delay periapical tissue repair[11] and increase the incidence of periapical periodontitis.[20] Studies have also shown that overextension of the filling material may influence the presence of Aspergillus mycetoma in the maxillary sinus,[21] particularly cement that contain zinc oxide in their composition.[22] Cases with overfilling usually end with surgical intervention.[23,24]

In both cases presented here, patients reported endodontic failure related to the presence of pain. The source of the pain was possibly misdiagnosed or misinterpreted or even confused the patients, leading them to demand a dental extraction. Unfortunately, many dentists perform extractions without the aid of radiographic examinations. In the cases presented here, radiopaque artifacts in the periapical radiographs could have been removed by alveolar curettage during extraction of the teeth involved, which may have prevented perpetuation of lesions. Love and Firth evaluated 100 periapical lesions and observed that 28% of them showed foreign materials being the same as the endodontic material.[25] Koppang et al. also observed foreign material in 31% of lesions diagnosed as periapical granulomas and cysts.[26] These findings confirm the potential risk of the development or exacerbation of periapical lesions due to extruded filling materials.

Overfilled material can act as a foreign body, causing pathophysiological responses, such as cell mutation, cytotoxicity, and chronic inflammation. In preexisting periapical lesions, the overfilled material can be colonized by microorganisms that hinder its eradication by the body’s immune system, even in cases of biocompatible materials, acting as a continuous source of infection and resulting in persistent pathology.[25] Nóbrega et al. showed a variety of Treponema in teeth with periapical lesions refractory to endodontic treatment. In our study, a microbiological analysis of the collected tissue samples was not possible. Therefore, we cannot rule out the presence of microorganisms associated with overfilling in these cases as a cause of failure of endodontic therapy.[27]

Material leaked from the root canal can move or migrate to the adjacent soft tissue or bone, causing severe symptoms.[4] Although fragments of the material can be removed by cell phagocytosis, in most cases, they need to be removed by a dentist.[28]In vitro studies have shown that the zinc oxide in gutta-percha is cytotoxic, and there is in vivo tissue irritation with an adjoining inflammatory reaction. Two tissue reactions have been observed with the use of gutta-percha. First, the large particles were encapsulated by collagen fibers, with the surrounding tissue remaining free of inflammatory cells. On the other hand, fine particles provoked an intense and localized tissue response, characterized by the predominance of macrophages and giant cells and isolated from the surrounding connective tissue by concentric layers of collagen fibers. Zinc oxide is one of the components of gutta-percha cones, where the leaching of zinc ions plays an important role in the cytotoxicity of this material, being associated with the inflammatory reaction of the surrounding tissues.[29]

Histopathological examination confirmed the diagnostic hypothesis for cases 1 (foreign body granuloma) and 2 (residual cyst). Access to periapical radiography in case 1 helped us understand that the overfilled material was a possible cause of granuloma, as there was no evidence of a periapical lesion. In case 2, multiple factors could be attributed to the endodontic failure such as the previous trauma that could compromise the teeth prior to the endodontic treatment or even an iatrogenic treatment, but we can only hypothesize since we could only rely on the patient’s statement. In the absence of microorganisms in the root canal or periapical tissues, perpetuation of lesions that prevent periapical healing after the endodontic treatment is related to irritation from foreign bodies.[30]

The present case report is one of the few that used microscopic techniques to identify the type of filling material associated with the lesion and tissue changes. The type of filling material associated with lesions was identified using polarized light and fluorescent light microscopy. Upon applying fluorescent light, gutta-percha shows fluorescent properties, as it is of plant origin. Birefringent granulations indicate the presence of calcium hydroxide in the sealer used for root canal filling. The inflammatory response persisted because of the large amount of overfilled material (gutta-percha and endodontic sealer), as a source of severe irritation associated with calcium hydroxide.[31,32]

Several studies have shown that the apical limit and type of filling material affect the healing process of endodontically treated teeth.[33,34] However, despite their biocompatibility, filling materials can favor endodontic treatment failure when overextended.[35] Another reason why endodontists should avoid extrusion of filling materials is the inconvenience they can cause to the patient, hours after the end of obturation, by triggering a painful inflammatory process, even if the materials are biocompatible. Negative experiences related to the endodontic treatment can traumatize the patient, and in some cases, make them opt for tooth extraction, and even discourage them from having future dental treatments.

The present case report shows the importance of filling the root canals with respect to the limit of the apical foramen and obtaining histological details, such as cell differentiation in infected and necrotic tissue in cases of extrusion of filling materials in the periapical region. In addition, histological confirmation of the diagnosis provides a better prognosis and patient satisfaction. Pathologists should understand the characteristics of endodontic lesions for an accurate diagnosis. This case report was prepared according to the PRICE 2020 guidelines [Figure 6].

F6
Figure 6:
PRICE 2020 Flowchart. FAPEAM: Funding - Amazonas Research Foundation

CONCLUSION

Recognizing the morphological and optical properties of endodontic lesions mixed with endodontic filling materials is essential for a precise and reliable histopathological report. The analysis of optical microscopy of fluorescent and polarized light proved to be an excellent tool to identify these filling materials. Endodontists may benefit of such investigation in order to better understand cases of endodontic failure or lesions resistant to conventional endodontic therapy.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

This study was financially supported by Amazonas Research Foundation (FAPEAM) (grant no. 012.2018 and no. 007.2020).

Conflicts of interest

There are no conflicts of interest.

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Keywords:

Endodontic treatment; filling material; light microscopy; oral lesion; overfilling

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