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.     

Therapy-resistant foreign body giant cell granuloma at the periapex of a root-filled human tooth

Although the primary etiological factor of periapical lesions is microbial, there are other independent factors that can adversely affect the outcome of endodontic treatment. In this communication, we present morphological evidence in support of the role of a foreign body reaction of periapical tissue to root-filling materials. The specimen consisted of a surgical biopsy of an asymptomatic periapical lesion which persisted after a decade of postendodontic follow-up. The biopsy was processed for correlated light and electron microscopy and was analyzed by various microtechniques. The unique feature of the lesion was the presence of vast numbers of large multinucleated cells and their cytoplasmic inclusion bodies. Morphologically, these multinucleated cells resembled foreign body giant cells. They contained characteristic birefringent cytoplasmic inclusions which on electron-probe X-ray microanalysis consistently revealed the presence of magnesium and silicon. The magnesium and silicon are presumably the remnants of a root-filling excess which protruded into the periapex and had been resorbed during the follow-up period. These observations strongly suggest that in the absence of microbial factors, root-filling materials which contain irritating substances can evoke a foreign body reaction at the periapex, leading to the development of asymptomatic periapical lesions that may remain refractory to endodontic therapy for long periods of time.     

Cholesterol As An Aetiological Agent In Endodontic Failures—A Review

Presence of cholesterol clefts in apical periodontitis lesions is a common histopathological observation. However, a potential aetiological association of cholesterol crystals to non-resolving apical periodontitis lesions after endodontic treatment has been suggested only recently. This article is an attempt to explain the biological basis for the inability of body cells to eliminate the local accumulation of cholesterol crystals, and to consolidate available clinical and experimental data in support of the view that massive accumulation of cholesterol crystals in inflamed periapical tissues can interfere with the periapical healing after conventional root canal treatment. As the irritating cholesterol crystals and certain other aetiological agents of failed endodontic treatment exist outside the root canal system, it is concluded that re-treatment alone, of such cases, is unlikely to resolve the factors that sustain the lesion. Apical surgery is indicated for successful management of such cases.     

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.     

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.     

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根管冲洗是根管预备中的重要环节。根管冲洗的主要目的是去除根管内容物、溶解病理组织、清除病原微生物、去除玷污层，避免根管预备过程中将感染物质推向深部或推出根尖孔。根管冲洗能否达到目的有赖于冲洗剂及冲洗技术的选择。本文主要介绍临床常用的根管冲洗剂及冲洗技术，旨在为，临床操作提供理论依据。     

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.     

Surgical management of a lateral lesion refractory to root canal retreatment caused by an extraradicular calculus. A case report

This article describes the management of a root canal-treated maxillary central incisor displaying a radiographic lateral radiolucency and a sinus tract that persisted irrespective of root canal retreatment following high standards. Endodontic microsurgery was indicated and curettage of the pathologic tissue revealed a calculus-like material attached to the outer root surface around the exit of a large lateral canal. A non-conventional approach was chosen: No root-end resection was conducted. Instead, the calculus was removed and the apical surface was scaled and smoothed, conserving the apical structure. Retrocavities were prepared in both lateral and apical foramens and filled with a bioceramic material. Follow-up examination showed optimal soft tissue healing. One-year follow-up of radiographs revealed healing of the lateral lesion. The lesion was diagnosed as a cyst, with an infected lumen. An exuberant calculus-like material attached to the external root surface was the most likely cause of the recalcitrant lateral periradicular lesion.     

Anatomic and microbiologic challenges to achieving success with endodontic treatment: a case report

This article describes a case of persistent apical periodontitis that required several nonsurgical and surgical approaches for resolution. A 28-year-old woman presented with a large symptomatic apical periodontitis lesion associated with the maxillary left lateral incisor that persisted in spite of previous nonsurgical and surgical endodontic treatment. Root canal retreatment was accomplished, but the lesion only showed a slight decrease in size after 18 months. Forty-six months after retreatment, the patient returned because of reemergence of symptoms. Radiographically, the lesion remained relatively unaltered. Periradicular resurgery was performed, and a biopsy specimen consisting of the lesion and the apical part of the root was collected for analysis. Radiographic and clinical reevaluation after 4 years revealed complete healing. Histopathologic and histobacteriologic observations demonstrated that the lesion was a cyst, and that the probable reason for failure was the occurrence of bacteria within dentinal tubules and in a lateral canal slightly coronal to the amalgam root-end filling. This case report clearly illustrates the difficulties imposed by anatomic complexities in attaining a disinfection level that is compatible with periradicular tissue healing.     

两种根管充填糊剂对犬根尖周组织修复的作用

目的：采用国产注射型自固化磷酸钙（CPC）与进口注射型氢氧化钙（Vitapex）作为根管充填材料，比较根尖周炎动物模型中CPC、Vitapex超填后，超填材料的吸收和根尖周组织的修复情况，为临床应用CPC提供理论依据。方法：选用3条健康成年杂种犬上、下颌P2、P3、M1共36个实验牙（共计78个根管），随机分为CPC组、Vitapex组及空白对照组。应用CPC、Vitapex作为根管充填材料，在人为造成根尖周炎后进行根管充填并使其超充，定期X线摄片，观察比较两种糊剂的吸收、根尖周稀疏区的变化，以及根尖周组织的修复情况。结果：CPC组、Vitapex组超填材料均可吸收，根尖周稀疏区缩小，两组材料组织切片显示在根尖孔附近均有新骨形成。CPC组根管内材料出现吸收情况较Vitapex组严重。结论：CPC糊剂对根尖周组织无刺激，适量超填可促进根尖周骨缺损修复，超填材料可完全吸收，但同时根管内充填糊剂亦存在吸收，其机制、意义、解决办法有待深入研究。     

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.     

MTA for obturation of mandibular central incisors with open apices: case report

The case reported demonstrates dramatic healing of the periapical region of retreated root canals with open apices by the successful use of mineral trioxide aggregate (MTA). Unsuccessful conventional root canal therapy for the mandibular central incisors had been followed by surgical treatment. The severely damaged root canals were obturated using MTA in anticipation of the formation of artificial apical plugs. The treated teeth were asymptomatic, and radiographic examination demonstrated apparent regeneration of periradicular tissue 2 years after the obturation. MTA can be considered a very effective material to promote regeneration of apical tissue, even in teeth with large open apices.     

Limitations of previously published systematic reviews evaluating the outcome of endodontic treatment

The aim of this work was to identify the limitations of previously published systematic reviews evaluating the outcome of root canal treatment. Traditionally, periapical radiography has been used to assess the outcome of root canal treatment with the absence of a periapical radiolucency being considered a confirmation of a healthy periapex. However, a high percentage of cases confirmed as healthy by radiographs revealed apical periodontitis on cone beam computed tomography (CBCT) and by histology. In teeth, where reduced size of the existing radiolucency was diagnosed by radiographs and considered to represent periapical healing, enlargement of the lesion was frequently confirmed by CBCT. In clinical studies, two additional factors may have further contributed to the overestimation of successful outcomes after root canal treatment: (i) extractions and re-treatments were rarely recorded as failures; and (ii) the recall rate was often lower than 50%. The periapical index (PAI), frequently used for determination of success, was based on radiographic and histological findings in the periapical region of maxillary incisors. The validity of using PAI for all tooth positions might be questionable, as the thickness of the cortical bone and the position of the root tip in relation with the cortex vary with tooth position. In conclusion, the serious limitations of longitudinal clinical studies restrict the correct interpretation of root canal treatment outcomes. Systematic reviews reporting the success rates of root canal treatment without referring to these limitations may mislead readers. The outcomes of root canal treatment should be re-evaluated in long-term longitudinal studies using CBCT and stricter evaluation criteria.     

Treatment of a Large Cystlike Inflammatory Periapical Lesion Associated with Mature Necrotic Teeth Using Regenerative Endodontic Therapy

Introduction

Regenerative endodontic therapy is currently used to treat immature permanent teeth with necrotic pulp and/or apical periodontitis. However, mature teeth with necrotic pulp and apical periodontitis have also been treated using regenerative endodontic therapy. The treatment resulted in resolution of apical periodontitis, regression of clinical signs and symptoms but no apparent thickening of the canal walls, and/or continued root development. A recent study in an animal model showed that the tissues formed in the canals of mature teeth with apical periodontitis after regenerative endodontic therapy were cementumlike, bonelike, and periodontal ligament–like tissue with numerous blood vessels. These tissues are similar to the tissues observed in immature permanent teeth with apical periodontitis after regenerative endodontic therapy.

Methods

A 23-year-old woman had a history of traumatic injury to her upper anterior teeth when she was 8 years old. Subsequently, #8 developed pulp necrosis and an acute apical abscess and #7 symptomatic apical periodontitis. The apex of #8 was slightly open, and the apex of #7 was completely formed. Instead of nonsurgical root canal therapy, regenerative endodontic therapy was attempted, including complete chemomechanical debridement on #8 and #7. This was based on the premise that filling of disinfected root canals with the host's biological vital tissue might be better than filling with foreign materials.

Results

After regenerative endodontic therapy of #8 and #7, there was radiographic evidence of periapical osseous healing and regression of clinical signs and symptoms. The pulp cavity of #8 decreased in size, and the apex closed. The pulp cavity of #7 appeared to be obliterated by mineralized tissue. These indicated ingrowth of new vital tissue into the chemomechanically debrided canals.

Conclusions

Regenerative endodontic therapy of mature teeth with apical periodontitis and apical abscess can result in the regression of clinical signs and/or symptoms and healing of apical periodontitis but no apparent thickening of the canal walls or continued root development. Filling of the disinfected canals with the host's vital tissue may be better than with foreign materials because vital tissue has innate and adaptive immune defense mechanisms.     

Deposition of calcified tissue around an overextended gutta-percha cone: case report

CASE REPORT: Root canal treatment was performed in a mandibular right second premolar with a periapical lesion and apical resorption. The root canal was prepared with K-files using the step-back technique and 3% NaOCl as an irrigant; during obturation gross overfilling of gutta-percha occurred. The tooth was permanently restored with a post and core along with a crown. Although healing of the periapical lesion occurred and the patient reported that he was symptom-free, the tooth was extracted after 4 years because of a subgingival root fracture. Following extraction the tooth was examined with SEM. The examination revealed the presence of newly formed calcified tissue at resorption sites on the root apex. This newly formed tissue extended from the surface of the root around the apex to the extruded gutta-percha cone to which it was well adapted, forming a bridge between the cone and the root.     

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.     

Risk analysis of failure of root canal treatment for teeth with inaccessible apical constriction

OBJECTIVE: The risk of failure of root canal therapy was assessed in teeth with inaccessible apical constriction and factors influencing treatment outcome in these teeth were analyzed. METHODS: From the same 57 patients, one tooth with inaccessible apical constriction (n=57) and one tooth with adequate accessibility (n=57) were included in this retrospective investigation. Cox regression analysis was used to analyze factors that may have influenced the outcome one or more years after obturation. These factors included inaccessibility, systemic disease, canal curvature, preoperative periradicular lesion, widening of periodontal ligament space, patient gender and age, size of master apical file, preoperative pulp vitality, years of operator experience and obturation length. RESULTS: Inaccessible apical constriction was a significant factor related to outcome (odds ratio, 5.301). Preoperative presence of periradicular lesion significantly influenced the outcome in cases with inaccessibility (odds ratio, 4.448). CONCLUSION: Inaccessibility increases the risk of root canal therapy failure particularly in teeth with preoperative periradicular lesion.     

恒牙根尖区解剖结构对根管治疗的影响

根管治疗的目的是彻底清除根管内感染物质,并严密充填根管,从而预防或治愈根尖周病变.恒牙根尖区解剖结构复杂,形态多样的根尖孔、弯曲根管、侧副根管等会对根管治疗各步骤产生影响,增加治疗难度,影响治疗效果.本文就恒牙根尖区解剖结构对根管治疗影响的研究进展进行综述.     

Clinical implications and microbiology of bacterial persistence after treatment procedures

Apical periodontitis is an infectious disease caused by microorganisms colonizing the root canal system. For an optimal outcome of the endodontic treatment to be achieved, bacterial populations within the root canal should be ideally eliminated or at least significantly reduced to levels that are compatible with periradicular tissue healing. If bacteria persist after chemomechanical preparation supplemented or not with an intracanal medication, there is an increased risk of adverse outcome of the endodontic treatment. Therefore, bacterial presence in the root canal at the time of filling has been shown to be a risk factor for posttreatment apical periodontitis. About 100 species/phylotypes have already been detected in postinstrumentation and/or postmedication samples, and gram-positive bacteria are the most dominant. However, it remains to be determined by longitudinal studies if any species/phylotypes persisting after treatment procedures can influence outcome. This review article discusses diverse aspects of bacterial persistence after treatment, including the microbiology, bacterial strategies to persist, the requisites for persisting bacteria to affect the outcome, and future directions of research in this field.