New perspectives on radicular cysts: do they heal?

During the past few decades several authors have perpetuated the notion that nearly half of all periapical lesions are radicular cysts. A few studies, based on meticulous serial sectioning of periapical lesions retrieved in toto, have shown that the actual incidence of radicular cyst is only about 15% of all periapical lesions. Equally significant was the discovery in 1980 and recent confirmation that radicular cysts exist in two structurally distinct classes namely, those containing cavities completely enclosed in epithelial lining (periapical true cysts) and those containing epithelium-lined cavities that are open to the root canals (periapical pocket cysts). From a clinical point of view a periapical pocket cyst may heal after conventional root canal therapy whereas an apical true cyst is less likely to be resolved without surgical intervention.     

Non‐microbial etiology: periapical cysts sustain post‐treatment apical periodontitis

IN MICROSCOPY, AS IN NATURE, ONE RECOGNIZES ONLY WHAT ONE ALREADY KNOWS. Routine histopathological diagnostic reports and publications based on retrospective reviewing of such, perpetuate the notion that nearly half of all apical periodontitis lesions are cysts. Studies based on meticulous serial sectioning of apical lesions retrieved in toto show that the actual prevalence of cysts is only about 15% of all apical periodontitis lesions. Periapical cysts exist in two structurally distinct classes, namely those containing cavities completely enclosed in epithelial lining (periapical true cysts) and those containing epithelium‐lined cavities that are open to the root canals (periapical pocket cysts). From a clinical point of view, small cysts, particularly the pocket cysts, can heal after non‐surgical root canal therapy whereas large cysts, mainly true cysts, are less likely to be resolved without surgical intervention.     

Prognosis of large cyst-like periapical lesions following nonsurgical root canal treatment: a clinical review

AIM: To evaluate clinically and radiographically the long-term clinical outcome of nonsurgical root canal treatment using calcium hydroxide in teeth with large cyst-like periapical lesions. SUMMARY: A total of 42 mature anterior teeth with large periapical lesions ranging in size from 7 to 18 mm in diameter were included in this study. Fluid samples from the lesions contained cholesterol crystals, which were identified by light microscopy. After adequate draining, the teeth were treated endodontically using calcium hydroxide as the intracanal medicament. All cases were followed up for a period of 2-10 years. Complete healing was observed in 73.8% and incomplete healing in a further 9.5% of cases. KEY LEARNING POINTS: Root canal treatment using calcium hydroxide as an antibacterial dressing was successful in healing large cyst-like periapical lesions. This study suggests that the size of a periapical lesion is not a major determining factor in the decision to perform conventional root canal treatment or surgical removal of the lesion. Even large cyst-like periapical lesions containing cholesterol crystals can heal following nonsurgical root canal treatment.     

On the causes of persistent apical periodontitis: a review

Apical periodontitis is a chronic inflammatory disorder of periradicular tissues caused by aetiological agents of endodontic origin. Persistent apical periodontitis occurs when root canal treatment of apical periodontitis has not adequately eliminated intraradicular infection. Problems that lead to persistent apical periodontitis include: inadequate aseptic control, poor access cavity design, missed canals, inadequate instrumentation, debridement and leaking temporary or permanent restorations. Even when the most stringent procedures are followed, apical periodontitis may still persist as asymptomatic radiolucencies, because of the complexity of the root canal system formed by the main and accessory canals, their ramifications and anastomoses where residual infection can persist. Further, there are extraradicular factors -- located within the inflamed periapical tissue -- that can interfere with post-treatment healing of apical periodontitis. The causes of apical periodontitis persisting after root canal treatment have not been well characterized. During the 1990s, a series of investigations have shown that there are six biological factors that lead to asymptomatic radiolucencies persisting after root canal treatment. These are: (i) intraradicular infection persisting in the complex apical root canal system; (ii) extraradicular infection, generally in the form of periapical actinomycosis; (iii) extruded root canal filling or other exogenous materials that cause a foreign body reaction; (iv) accumulation of endogenous cholesterol crystals that irritate periapical tissues; (v) true cystic lesions, and (vi) scar tissue healing of the lesion. This article provides a comprehensive overview of the causative factors of non-resolving periapical lesions that are seen as asymptomatic radiolucencies post-treatment.     

The periapical space--a dynamic interface

The ultimate aim of endodontic treatment is to encourage the healing of apical periodontitis, or to prevent it from occurring if it was not present prior to treatment. Apical periodontitis is a general term used to describe an inflammatory response to irritation caused by the contents of a root canal system and it has several distinct forms. The most common is a granuloma but this can develop into other disease entities such as an abscess, a periapical pocket cyst or a true cyst, all of which present as radiolucencies. However, periapical radiolucencies may also be caused by extra-radicular infections, foreign body reactions and periapical scars, or they may be due to other tumours and cysts that have not originated from pulp disease. Practitioners must recognise and understand the different pathological entities and the dynamic interactions that occur in the periapical tissues in order to correctly diagnose and treat these conditions.     

Inflammatory profile of chronic apical periodontitis: a literature review

Apical periodontitis caused by root canal infection is the most frequent pathological lesion in the jaws, mainly manifested as periapical granulomas and cysts. Understanding of the formation and progression of apical periodontitis as well as the identification of inflammatory biomarkers can help increase the knowledge of pathogenic mechanisms, improve the diagnosis and provide support for different therapeutic strategies. The objective of the present article is to review inflammatory biomarkers such as cytokines, chemokines, inflammatory cells, neuropeptides, RANK/RANKL/OPG system and other inflammatory markers and to relate these systems to the development and progression of pathological conditions related to apical periodontitis.     

Ciliated epithelium-lined radicular cysts

OBJECTIVE: This report describes 3 cases of ciliated epithelium-lined radicular cysts among 256 apical periodontitis lesions and also illustrates the occurrence of an Actinomyces-infected periapical cyst. STUDY DESIGN: Serial and step serial sections of 256 plastic-embedded root apices with attached apical periodontitis lesions that were prepared for a previous investigation were reviewed for the presence of ciliated epithelium-lined radicular cysts. The lesions that were found to have such epithelial lining were examined in a transmission electron microscope to elaborate the fine structure of the ciliated cells. RESULTS: A total of 3 ciliated columnar epithelium-lined cysts was found among the 256 apical periodontitis lesions examined. Two of the lesions also contained stratified squamous epithelium. All 3 lesions affected maxillary premolars. One of the lesions was a true cyst, and the other 2 were periapical pocket cysts. The lumen of 1 of the latter revealed the presence of typical "ray-fungus" actinomycotic colonies. CONCLUSION: Although the stratified squamous component of the epithelia that lined the radicular cysts reported here may be derived from the cell rests of Malassez, the ciliated epithelial cells may be of sinus origin. Microbial agents from diseased root canals can advance into radicular cysts, particularly in pocket cysts, with the possible threat of such infection in upper posterior teeth spreading into the maxillary sinus.     

Nonsurgical endodontic treatments in molar teeth with large periapical lesions in children: 2-year follow-up

Profound caries lesions may lead to invasion of microorganisms to the dental pulp, and periapical areas can promote the development of dentoalveolar abscess and periapical bone loss. Treatment options to manage large periapical lesions range from nonsurgical root canal treatment and/or apical surgical procedure to extraction. Young molar teeth with pulp necrosis and large periapical lesions in children are frequently treated with root canal treatment because the therapy is more difficult in multirooted teeth. In these case reports, nonsurgical endodontic treatments performed on 6 molar teeth with large periapical lesions, by repeated intracanal dressing with calcium hydroxide, are presented. Radiographs displayed significant bony healing at the end of the second year. In conclusion, large periapical lesions can respond favorably to nonsurgical treatment, and complex and difficult endodontic treatments in children might not be required.     

“True” Versus “Bay” Apical Cysts: Clinical,Radiographic, Histopathologic,and Histobacteriologic Features

IntroductionThis study compared the main clinical, radiographic, and histologic features of true and bay apical cysts.MethodsThe study material comprised 95 biopsy specimens of apical periodontitis lesions obtained attached to the root tip of both untreated and root canal–treated teeth. Clinical and radiographic data were recorded. Specimens were obtained by extraction or periradicular surgery and were meticulously processed for histopathologic and histobacteriologic methods. All cases diagnosed as apical cysts (n = 23) were divided into the true and bay types, which were then compared for tooth location, patient’s sex, lesion size, severity of clinical symptoms, presence of a sinus tract, previous abscess episodes, and prevalence of bacteria in the main root canal lumen and ramifications, on the outer root surface, and within the cyst cavity.ResultsEleven specimens were classified as true (48%) and 12 (52%) as bay cysts. Bacteria were found in all specimens, regardless of the histopathologic diagnosis. Planktonic bacteria were observed in the main root canal in all true cysts and in 11 of 12 (92%) bay cyst cases. Biofilms were detected in the main canal in 10 cases from each diagnostic group and were frequently observed in ramifications. Extraradicular biofilms occurred in a few specimens only. Bacteria were visualized within the cavity of both true (4/11, 36%) and bay (6/12, 50%) cyst specimens. The severity of histologic inflammation was always high. There were no significant differences between true and bay cysts for all the clinical, radiographic, histopathologic, and histobacteriologic parameters assessed.ConclusionsExcept for the morphologic relationship of the cyst cavity with the root canal space, true and bay cysts exhibited no other significant differences in the various parameters evaluated. The 2 cyst types were always associated with an intraradicular infection and sometimes with an extraradicular infection. Findings question the need to differentiate true and bay cysts and do not support the assumption that true cysts are self-sustainable entities not maintained by infection.     

较大根尖囊状病变的非手术根管治疗疗效分析

目的 分析较大根尖囊状病损的非手术根管治疗的疗效。方法 自2015年1月至2020年12月就诊于南京医科大学附属口腔医院的根尖透射影最大径大于10mm，边界清析根尖囊状病损的60例，其中A组32例患牙仅通过规范完善的根管治疗，B组28例在进行完善根管治疗后进行外科病变清除术，术后进行定期随访观察。结果 经过3-18月的随访，A组32例患者中12例愈合，16例改善，4例根尖未见明显变化，有效率达87.5%；B组28例患者治愈16例，好转12例，有效率达100%。经统计学检验，两组间没有显著性差异（P>0.05）。结论 非手术治疗对根尖周囊状病损有较高的成功率。在没有急性症状的较大根尖囊状病变的患牙，非手术治疗应作为首选治疗方法。     

Periapical cyst repair after nonsurgical endodontic therapy--case report

This article presents the procedures that must be considered for periapical cyst repair after nonsurgical endodontic treatment. The case of a periapical cyst associated to the left maxillary lateral incisor is reported. Nonsurgical root canal therapy was performed and lesion healing was confirmed radiographically after 24 months. Differential diagnosis, endodontic infection control, apical foramen enlargement and filling of the cystic cavity with a calcium hydroxide paste were important procedures for case resolution.     

Proliferation of epithelial cell rests, formation of apical cysts, and regression of apical cysts after periapical wound healing

There is continuing controversy regarding the potential for inflammatory apical cysts to heal after nonsurgical endodontic therapy. Molecular cell biology may provide answers to a series of related questions. How are the epithelial cell rests of Malassez stimulated to proliferate? How are the apical cysts formed? How does the lining epithelium of apical cysts regress after endodontic therapy? Epithelial cell rests are induced to divide and proliferate by inflammatory mediators, proinflammatory cytokines, and growth factors released from host cells during periradicular inflammation. Quiescent epithelial cell rests can behave like restricted-potential stem cells if stimulated to proliferate. Formation of apical cysts is most likely caused by the merging of proliferating epithelial strands from all directions to form a three-dimensional ball mass. After endodontic therapy, epithelial cells in epithelial strands of periapical granulomas and the lining epithelium of apical cysts may stop proliferating because of a reduction in inflammatory mediators, proinflammatory cytokines, and growth factors. Epithelial cells will also regress because of activation of apoptosis or programmed cell death through deprivation of survival factors or by receiving death signals during periapical wound healing.     

Persistent apical periodontitis associated with a calcifying odontogenic cyst

Aim  To report a case of calcifying odontogenic cyst (COC) that was suggestive of apical periodontitis adjacent to the roots of the maxillary incisor teeth.
Summary  Tooth 21 presented with clinical and radiographic signs of secondary infection, a post within the root canal and substantial internal tooth destruction; it was scheduled for endodontic surgery. Teeth 12 and 22 were root filled following the placement of a calcium hydroxide intracanal dressing for 21 days. Three attempts at root canal disinfection in tooth 11 were unsuccessful, and a persistent purulent drainage precluded completion of root canal treatment. Surgical enucleation of the periapical lesion was undertaken and the tissues submitted for histopathological examination. A diagnosis of COC was established based on the microscopic analysis. COC is an unusual benign lesion that represents 2% of all odontogenic lesions. Depending on the stage of development, it can mimic a large lesion associated with apical periodontitis and should therefore be considered in the differential diagnosis. In the case of COC, the definitive diagnosis can only be made with histopathological analysis.
Key learning points  • Persistent apical periodontitis may be of nonendodontic origin.
• Histological examination is essential to establish the cause of persistent apical periodontitis.
• Calcifying odontogenic cyst can mimic apical periodontitis.     

Differences in Inflammation and Bone Resorption between Apical Granulomas,Radicular Cysts,and Dentigerous Cysts

IntroductionDental cysts can be of inflammatory (radicular cysts) or noninflammatory (dentigerous cysts) origin. Apical periodontitis is a necrosis of the pulp and infection of the root canal causing the development of apical granulomas or radicular cysts. The immunology of granuloma and cyst formation is important because modern root filling materials are immunologically active and can contribute to the resolution of apical granulomas. In contrast, radicular cysts often require apicectomy. A better understanding of the pathophysiology of inflammation and bone resorption in apical periodontitis could be the basis for developing new root filling materials with superior immunomodulatory properties.MethodsForty-one apical granulomas, 23 radicular cysts, and 23 dentigerous cysts were analyzed in this study. A tissue microarray of the 87 consecutive specimens was created, and human leukocyte antigen–DR isotype (HLA-DR)-, CD83-, receptor activator of nuclear factor kappa B ligand–, macrophage colony-stimulating factor (MCSF)-, galectin-3 (Gal3)-, CD4-, and CD8-positive cells were detected by immunohistochemistry. Tissue microarrays were digitized, and the expression of markers was quantitatively assessed.ResultsHLA-DR, CD83, MCSF, and Gal3 expression was significantly (P < .05) higher in radicular cysts compared with apical granulomas. HLA-DR, CD83, MCSF, receptor activator of nuclear factor kappa B ligand, and Gal3 expression in dentigerous cysts was significantly (P < .05) lower than in both periapical lesions (apical granulomas and radicular cysts). CD4 and CD8 infiltration was not statistically different between apical granulomas and radicular cysts. Dentigerous cysts showed a significantly (P < .05) lower T-cell infiltration than apical periodontitis. The CD4/CD8 ratio was not significantly different between the analyzed groups.ConclusionsThe development of radicular cysts in apical periodontitis is associated with an increased expression of myeloid inflammatory markers and bone resorption parameters. Antigen-presenting cells and myeloid cells might be more relevant for the pathogenesis of apical periodontitis than T cells. Increased inflammation might promote the formation of radicular cysts and more pronounced bone resorption.     

Enhancement of Healing Kinetics of Periapical Lesions in Dogs by the Apexum Procedure

In nonsurgical endodontic procedures, the healing of apical periodontitis is achieved by treatment provided within the root canal system. The new Apexum procedure is based on advancing the debridement one step further by minimally invasive removal of the inflamed periapical tissues through root canal access, thereby enhancing the healing kinetics of periapical lesions. The Apexum procedure uses 2 sequential rotary devices designed to extend beyond the apex and to mince periapical tissues on rotation in a low-speed handpiece, followed by washing out the minced tissue. This initial animal study was conducted to evaluate the efficacy and potential adverse effects of this procedure. Periapical lesions were induced in the lower premolars in dogs by placement of autologous dental plaque and subsequent radiographic verification. Fifty roots with periapical lesions were then subjected to cleaning, shaping and disinfection of their root canals, using a conventional root canal treatment protocol. Teeth in group 1 were subjected to the new Apexum procedure just before obturation, whereas roots in group 2 were subjected to no additional intervention before obturation. Clinical and radiographic follow-ups were carried out for 6 months. Radiographic healing of the periapical lesions in dogs at 3 and 6 months showed significantly enhanced kinetics in the Apexum-treated group compared with the conventional treatment group, at both time points (p <0.01). No noticeable adverse events occurred in either of the groups. This new procedure might significantly enhance healing kinetics of apical periodontitis compared with conventional nonsurgical endodontic treatment.     

Calculus-like deposit on the apical external root surface of teeth with post-treatment apical periodontitis: report of two cases

AIM: To report two cases in which calculus-like material was found on external root surfaces of (i) an extracted root and (ii) an apicected part of a root, both of which were removed due to post-treatment refractory apical periodontitis. SUMMARY: In each case, there was a fistulous tract, which did not heal after conventional root canal treatment. The first case did not heal even after apical surgery, and subsequent tooth extraction revealed calculus-like material on a root surface of complex anatomy. The second case showed radiographic signs of healing after apicectomy. Histology of the apical biopsy revealed a calculus-like material on the external surface of the root apex. It is suggested that the presence of calculus on the root surfaces of teeth with periapical lesions may contribute towards the aetiology of failure. KEY LEARNING POINTS: Biofilm on the external root surface has been implicated in the failure of apical periodontitis to heal, despite adequate root canal treatment. Calculus-like material was found, in two cases, on the root surface of teeth with post-treatment apical periodontitis, where the only communication externally was a sinus tract.     

Repair of Extensive Apical Root Resorption Associated with Apical Periodontitis: Radiographic and Histologic Observations after 25 Years

Introduction

Root resorption is a frequent finding in teeth with apical periodontitis. In cases of severe apical periodontitis, root resorption may involve not only cementum but also dentin. Resorbed tooth structures can only be repaired with cementum because stem cells in the periradicular tissues are not capable of differentiating into odontoblasts. This article reports the repair of extensive apical root resorption associated with apical periodontitis 25 years after treatment.

Methods

A 51-year-old man presented with pulp necrosis and symptomatic apical periodontitis in tooth #7. The periapical radiograph showed a large radiolucent periradicular lesion and severe root resorption. Nonsurgical root canal therapy was performed. Twenty-five years after treatment, a crown fracture developed, and the tooth could not be restored. The periapical radiograph revealed complete healing of the previous apical periodontitis lesion and restoration of the resorbed root structure. The tooth was removed and examined histologically.

Results

The apical canal was almost completely filled with a cementumlike tissue with some strands of entrapped vital uninflamed connective tissue. Areas of cementum and dentin resorption in the apical third were repaired by a combination of cellular and acellular cementum to which periodontal ligament fibers were attached.

Conclusions

Root resorption caused by apical periodontitis can be restored almost to its normal structure after adequate nonsurgical root canal treatment that succeeded in controlling infection. The mechanisms behind this process are not clear but probably involve signaling pathways regulating root development, cell-cell and cell-matrix interaction, and morphogens.     

Consequences of and strategies to deal with residual post-treatment root canal infection

Bacterial sampling of prepared root canals is used to determine the presence and character of the remaining microbiota. However, it is likely that current sampling techniques only identify organisms in the main branches of the root canal system whereas it is unlikely that they can sample areas beyond the apical end-point of preparation and filling, or in lateral canals, canal extensions, apical ramifications, isthmuses and within dentinal tubules. Thus, it may be impossible by current techniques to identify residual post-treatment root canal infection. In histologic observations of root apices, bacteria have been found in inaccessible inter-canal isthmuses and accessory canals often in the form of biofilms. There is no in vivo evidence to support the assumption that these bacteria can be entombed effectively in the canal system by the root filling and thus be rendered harmless. As a consequence of this residual root infection, post-treatment apical periodontitis, which may be radiographically undetectable, may persist or develop as a defence mechanism to prevent the systemic spread of bacteria and/or their byproducts to other sites of the body. Histologic observation of root apices with surrounding bone removed from either patients or human cadavers has demonstrated that post-treatment apical periodontitis is associated with 50-90% of root filled human teeth. Thus, if the objective of root canal treatment is to eliminate apical periodontitis at a histological level, current treatment procedures are inadequate. It is essential that our knowledge of the local and systemic consequences of both residual post-treatment root infection and post-treatment apical periodontitis be improved. The continued development of treatments that can effectively eliminate root infection is therefore a priority in clinical endodontic research. Post-treatment disease following root canal treatment is most often associated with poor quality procedures that do not remove intra-canal infection; this scenario can be corrected via a nonsurgical approach. However, infection remaining in the inaccessible apical areas, extraradicular infection including apically extruded dentine debris with bacteria present in dentinal tubules, true radicular cysts, and foreign body reactions require a surgical intervention.     

Root canal treatment of an immature dens invaginatus with apical periodontitis: a case report

The purpose of this paper was to describe the case of an 11-year-old patient who presented a dens invaginatus, detected in the permanent maxillary left lateral incisor, with an immature open apex and extensive apical periodontitis and sinus tract. The mineralized invaginated barrier was removed, and a nonsurgical root canal treatment was performed using both calcium hydroxide as a root canal dressing to stimulate apexification and a mineral trioxide aggregate (MTA) plug to permit root canal filling. After a 14-month period of root canal dressing changes, no evidence of apical periodontitis was observed, and the MTA plug was placed in the root canal's apical portion. The root canal filling was performed using the thermoplasticized gutta-percha technique. At the 12-month follow-up, complete radiographic periapical healing, characterized by bone formation in the area around the tooth apex, and no clinical or radiographic evidence of refractory apical periodontitis were detected.