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.     

锥形束CT与根尖片对beagle犬显微根尖手术的预后评估

目的:采用根尖片和锥形束CT(cone beam computed tomography, CBCT)对beagle犬实验性根尖周炎显微根尖手术的预后进行评估。方法:将3条beagle犬18颗前磨牙髓腔暴露于口腔环境中8周, 拍摄根尖片及CBCT显示36个牙根均形成实验性根尖周炎。根管治疗后行显微根尖外科手术,术后即刻、6月分别拍摄根尖片和CBCT,根据根尖片和CBCT的根尖透射影像面积,比较二者在识别根尖骨质缺损的差别。结果:显微根尖手术后即刻CBCT矢状面、冠状面根尖透射影像面积均大于根尖片,差别具有统计学意义(P=0.000,P=0.026);CBCT矢状面、冠状面比较两组间差别无统计学意义(P=0.070)。显微根尖手术后6月复查CBCT矢状面、冠状面根尖透射影像面积均大于根尖片,差别具有统计学意义(P=0.000,P=0.012);CBCT矢状面根尖透射影像面积大于冠状面,两组间差别有统计学意义(P=0.001)。结论:CBCT在根尖周骨质缺损的识别优于根尖片,CBCT在根尖手术骨缺损预后评估中是一项有效的评价手段。     

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.     

Resolution of Apical Periodontitis-induced Mental Nerve Paresthesia Through Nonsurgical Endodontic Retreatment: A Case Report

Paresthesia is a potential consequence of unsuccessful root canal treatment. Persistent infection resulting in apical periodontitis may enlarge sufficiently to involve the mental neurovascular bundle. The case presented in this report was referred for endodontic evaluation with a chief complaint of discomfort on mastication and persistent numbness of the lower left lip. Clinical and radiographic evaluation revealed incomplete primary endodontic treatment of the left mandibular second premolar with complex internal anatomy. The untreated root canal system resulted in the progression of apical periodontitis involving the left mental neurovascular bundle as confirmed by cone-beam computed tomography imaging. Nonsurgical root canal retreatment was performed over 2 visits. At the 3-year follow-up visit, the paresthesia had resolved with return of normal sensation. Nonsurgical endodontic retreatment may be sufficient to allow healing of large periapical lesions and resolve complications including paresthesia without the need for surgical intervention.     

Nonsurgical Root Canal Therapy of Large Cyst-like Inflammatory Periapical Lesions and Inflammatory Apical Cysts

It is a general belief that large cyst-like periapical lesions and apical true cysts caused by root canal infection are less likely to heal after nonsurgical root canal therapy. Nevertheless, there is no direct evidence to support this assumption. A large cyst-like periapical lesion or an apical true cyst is formed within an area of apical periodontitis and cannot form by itself. Therefore, both large cyst-like periapical lesions and apical true cysts are of inflammatory and not of neoplastic origin. Apical periodontitis lesions, regardless of whether they are granulomas, abscesses, or cysts, fail to heal after nonsurgical root canal therapy for the same reason, intraradicular and/or extraradicular infection. If the microbial etiology of large cyst-like periapical lesions and inflammatory apical true cysts in the root canal is removed by nonsurgical root canal therapy, the lesions might regress by the mechanism of apoptosis in a manner similar to the resolution of inflammatory apical pocket cysts. To achieve satisfactory periapical wound healing, surgical removal of an apical true cyst must include elimination of root canal infection.     

Reasons for persistent and emerging post‐treatment endodontic disease

This article is a critical review of the reasons for persistent and emerging post‐treatment endodontic disease (PTED). While there is a strong consensus that micro‐organisms, mainly bacteria, are practically the only cause of primary apical periodontitis, the reasons for persistent apical periodontitis lesions have been more a matter of debate. The authors of this review focus on the role of micro‐organisms in PTED, and while secondary developments such as cholesterol crystals or foreign material in the periapical area of a tooth with apical periodontitis may contribute to additional irritation and/or an inflammatory reaction, a detailed analysis of the available data suggests that evidence supporting a primary role for such secondary factors without the continued presence of bacteria is lacking. Therefore, even in PTED, elimination of micro‐organisms residing within the tooth structure, root surface, or periapical tissues remains the goal of treatment and the key to long‐term success.     

Microorganisms in root canal infections: a review

A traditional concept is that apical periodontitis is the result of pathogenic effects of the microorganisms colonizing the root canal system and the response of the host defence system. The composition of the microflora of root canals differs in primary endodontic treatment and retreatment cases. Persistent disease in the periapical region after root canal treatment presents a more complex situation as it was thought earlier. Scientific evidence indicates that unsatisfactory outcome of cases in which treatment has followed the highest technical standards mainly is associated with microbial factors, comprising extraradicular and/or intraradicular infections.     

Prevalence of Apical Periodontitis in Root Canal–Treated Teeth From an Urban French Population: Influence of the Quality of Root Canal Fillings and Coronal Restorations

This cross-sectional study determined the prevalence of apical periodontitis in 1035 root canal–treated teeth from adult French patients and investigated the influence of the quality of canal fillings and coronal restorations on the periradicular status. Periapical radiographs were used for analyses, and teeth were classified as healthy or diseased according to the periapical index scoring system. Overall, the prevalence of apical periodontitis in root canal–treated teeth was 33%. Only 19% of the teeth had endodontic treatments rated as adequate. The success rate (number of healthy teeth) for cases with adequate endodontic treatment was 91%, which was significantly higher when compared with teeth with inadequate treatment (61%). Teeth with adequate restorations had significantly decreased prevalence of apical periodontitis (29%) as compared with teeth with inadequate restorations (41%). The combination of adequate endodontic treatment and adequate restorations yielded the highest success rate (93.5%). The quality of the endodontic treatment was the most important factor for success, although the quality of the coronal restoration also influenced the treatment outcome.     

Intraradicular bacteria and fungi in root-filled, asymptomatic human teeth with therapy-resistant periapical lesions: a long-term light and electron microscopic follow-up study

Light and electron microscopy were used to analyze nine therapy-resistant and asymptomatic human periapical lesions, which were removed as block biopsies during surgical treatment of the affected teeth. The cases that required surgery represented about 10% of all of the cases which received endodontic treatment and root fillings during the period 1977 to 1984. These cases revealed periapical lesions when they were examined 4 to 10 yr after treatment. The biopsies were processed for correlated light and electron microscopy. Six of the nine biopsies revealed the presence of microorganisms in the apical root canal. Four contained one or more species of bacteria and two revealed yeasts. Of the four cases in which bacteria were found, only in one biopsy could they be found by light microscope. In the other three specimens, the bacterial presence could be confirmed only after repeated electron microscopic examination of the apical root canal by serial step-cutting technique. Among the three cases in which no microorganisms could be encountered, one showed histopathological features of a foreign body giant cell granuloma. These findings suggest that in the majority of root-filled human teeth with therapy-resistant periapical lesions, microorganisms may persist and may play a significant role in endodontic treatment failures. In certain instances such lesions may also be sustained by foreign body giant cell type of tissue responses at the periapex of root-filled teeth.     

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??Chronic periapical periodontitis??CAP??is a common kind of chronic inflammation of periapical tissue. Under the conditions of failure of root canal treatment or retreatment??serious variation of root canal anatomy and definite diagnosis after exploratory operation??endodontic microsurgery has its unique application value. This paper summarized the current situation of clinical application and development trend of microscopic endodontic microsurgery in the treatment of chronic periapical periodontitis??providing references to the diagnosis and treatment of chronic periapical periodontitis in clinical work.     

Calculus-like deposit at apex of tooth with refractory apical periodontitis

Abstract— It is generally accepted that bacteria in or outside the root canal are the reason for apical periodontitis and endodontic failures. This case report presents a 60-year-old woman with a periapical lesion and a fistulous tract which did not respond to conventional root canal treatment. During periapical surgery, granulomatous tissue was removed and a calculus-like deposit was observed on the root surface. A radicular cyst was diagnosed. Nine months after this calculus-like deposit had been removed and the cyst enucleated, complete recovery of the bone had occurred. It is suggested that the presence of the calculus-like deposit at the apex of the tooth or its effects may in part have delayed the healing of the periapical inflammation in spite of apparently adequate endodontic treatment.     

根尖显微外科手术治疗慢性根尖周炎研究进展

慢性根尖周炎（CAP）是一类常见的根尖周围组织慢性炎症反应,在根管治疗或再治疗失败、根管解剖严重变异或需通过探查手术明确诊断等情况下,显微根管外科有其独特的应用价值。本文综述了CAP治疗中根尖显微外科手术的临床应用现状及发展趋势,为临床工作中对CAP的诊断和治疗提供参考。     

Radicular cyst affecting a root-filled human tooth: a long-term post-treatment follow-up

Apical periodontitis is caused primarily by microorganisms residing in the root canals of affected teeth. Nevertheless, there is convincing evidence implicating other independent factors that adversely affect the outcome of conventional root canal therapy. In this paper, morphological evidence is presented in support of die potential role of two endogenous factors that may interfere with post-endodontic healing of the periapex. The specimens consisted of a surgical biopsy of an asymptomatic peri-apical lesion which persisted for a follow-up period of 44 months. The biopsy was processed for correlated light and electron microscopy. The lesion was characterized by the presence of a large central lumen lined by a stratified squamous epithelium. The most striking feature of the lesion was the presence of vast numbers of cholesterol crystals which congregated in the connective tissue surrounding the cyst cavity. Extensive light and electron microscopic investigation of the apical part of the root canal and the lesion foiled to reveal the presence of microorganisms. These findings strongly suggest that intrinsic factors like the accumulation of certain tissue break-down products such as cholesterol crystals, and the cystic condition of the lesion itself, can adversely affect the healing process of the periapex following root canal therapy. Consequently, such apical lesions can remain refractory to conventional endodontic therapy for long periods of time.     

Clinical, radiographic and histological evaluation of chronic periapical inflammatory lesions

The aim of the present study was to comparatively evaluate the clinical, radiographic and histological aspects of chronic inflammatory periapical lesions. One hundred and sixty-four lesions of human teeth, independent of age, race and sex, were evaluated by clinical, radiographic and histological analyses conducted after surgical endodontic treatment. Our results showed that there was uniformity in the interference factors on the evolution of periapical healing such as the apical biofilm and/or endogenous (cholesterol crystals) or exogenous (extruded endodontic materials that are indigestible or of difficult digestion) foreign bodies and that some cysts are reversible with endodontic treatment. We conclude that it is difficult for the clinician to adjust parameters defining a diagnosis of chronic inflammatory periapical lesions.     

An Innovative Regenerative Endodontic Procedure Using Leukocyte and Platelet-rich Fibrin Associated with Apical Surgery: A Case Report

Regenerative endodontic procedures (REPs) associated with apical surgery could represent an alternative treatment strategy for patients whose teeth present incomplete root formation and extensive apical lesions. Leukocyte platelet-rich fibrin (L-PRF) has potential benefits in REPs; it could promote apical root formation and optimal bone healing. The aim of this case report was to describe innovative regenerative endodontic therapy using L-PRF in the root canal and an extensive apical lesion in an immature tooth with dens invaginatus and asymptomatic apical periodontitis. A healthy 20-year-old woman was referred to the dental clinic of the Universidad de Los Andes, Santiago, Chile, for endodontic treatment in tooth # 22 with incomplete root development and an extensive apical lesion. The diagnosis was asymptomatic apical periodontitis associated with dens invaginatus type II. The patient was treated with an innovative approach using L-PRF in REPs associated with apical surgery. Follow-ups were performed at 6 months and 1 year later. They included periapical radiographs, cone-beam computed tomographic imaging, sensitivity, and vitality tests. The clinical evaluations performed at 6 months and 1 year revealed an absence of symptoms. The radiographic evaluations showed that the apical lesion was resolved. The cone-beam images indicated that the root length increased and the walls had thickened. The sensitivity tests were positive, and the laser Doppler flowmetry showed positive blood flow after 1 year. The success of the results in this case report indicate that L-PRF can be used as a complement in apical surgery and REPs and could provide an innovative alternative treatment strategy for complex clinical cases like these.     

一次性和多次性根管治疗应用于根尖周炎的临床评价

目的评价根管治疗一次法和多次法对无症状根尖周炎疗效的影响,探讨一次性根管治疗的适应症。方法选取无症状根尖周炎的患牙160颗,分层随机法分为两组,分别采用一次法和多次法完成根管治疗。所有患牙均使用镍钛机动根管器械预备,牙胶冷侧方加压法充填根管。比较两组术后疼痛发生情况,根据患者主观症状、临床表现和术前术后X线片评价疗效。结果一次法和多次法在术后疼痛、根管治疗效的差异上没有统计学意义。结论一次性根管治疗应用于无症状根尖周炎的患牙是可行的,但要注意控制适应症。     

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.     

Regenerative Endodontic Procedures for Traumatized Immature Permanent Teeth with Severe External Root Resorption and Root Perforation

External root resorption (ERR) is often a complication of traumatic injury to the teeth. Traditionally, external inflammatory root resorption is treated with calcium hydroxide. The outcome of ERR, especially replacement resorption, is unpredictable. The purpose of the present case report was to describe regenerative endodontic procedures (REPs) for 1 replanted avulsed tooth with severe external root resorption and root perforation (tooth #9) and 1 extruded tooth (tooth #8). A 9-year-old girl was referred for the treatment of teeth #8 and #9 4 months after the initial trauma. Clinical examination showed that tooth #9 had a sinus tract present near the periapical area, was tender to percussion and palpation, and did not respond to pulp sensibility tests. Tooth #8 responded to pulp sensibility tests. Periapical radiographic and cone-beam computed tomographic examination showed that tooth #9 had a periapical radiolucent lesion and severe ERRs with a root perforation. Tooth #9 was diagnosed with a necrotic pulp and symptomatic apical periodontitis. Regenerative endodontic procedures (REPs) were initiated. Tooth #8 became nonresponsive to pulp sensibility tests and developed a periapical lesion 12 months after REPs of tooth #9 and was also treated with REPs. The clinical symptoms and apical lesions resolved for both teeth after REPs. The severe ERRs were arrested, and root perforation was repaired for tooth #9. Teeth #8 and #9 underwent canal obliteration by hard tissue formation after REPs and were in function at 18 months and 30 months, respectively. REPs may be used to manage traumatized immature permanent teeth with a necrotic pulp and apical periodontitis associated with severe ERR and root perforation.     

One-appointment endodontic therapy: biological considerations

BACKGROUND: The authors conducted a literature review to present the best available biological evidence concerning one-appointment endodontic therapy for asymptomatic teeth with apical periodontitis. TYPES OF STUDIES REVIEWED: Because of recent advances in technology, such as rotary engines and nickel-titanium instruments, some practitioners are performing one-appointment endodontic therapy for asymptomatic teeth with apical periodontitis. The authors reviewed the literature, which revealed only a small number of randomized, controlled clinical trials that have been conducted on one-appointment versus multiple-appointment endodontic therapy. RESULTS: As the apical canal preparation is enlarged, a greater percentage of bacteria is eradicated from infected root canals. In addition, sufficiently large apical root canal enlargement facilitates the delivery of antimicrobial irrigant to the apical portion of the canal. However, an association between positive or negative preobturation root canal culture results and the outcome of endodontic treatment has not been well-established. CLINICAL IMPLICATIONS: The best available evidence, based on a systematic literature review, indicates that one-appointment endodontic therapy may be feasible in selected cases of apical periodontitis in asymptomatic teeth. However, additional randomized, controlled clinical trials are required.