Influence of residual bacteria on periapical tissue healing after chemomechanical treatment and root filling of experimentally infected monkey teeth

The purpose of this study was twofold: first, to determine the influence on the healing of the periapical tissues when selected bacterial strains and combinations thereof remain after root canal treatment; and, second, the relationship to healing of the quality of the root filling. In eight monkeys, 175 root canals, previously infected with combinations of four or five bacterial strains and with radiographically verified apical periodontitis, were endodontically treated, bacteriologically controlled, and permanently obturated. After 2-2.5 yr, the periapical regions were radiographically and histologically examined. Of these teeth, 48 root canals were also examined for bacteria remaining after removal of the root fillings. When bacteria remained after the endodontic treatment, 79% of the root canals showed non-healed periapical lesions, compared with 28% where no bacteria were found. Combinations of residual bacterial species were more frequently related to non-healed lesions than were single strains. When no bacteria remained, healing occurred independently of the quality of the root filling. In contrast, when bacteria remained, there was a greater correlation with non-healing in poor-quality root fillings than in technically well-performed fillings. In root canals where bacteria were found after removal of the root filling, 97% had not healed, compared with 18% for those root canals with no bacteria detected. The present study demonstrates the importance of obtaining a bacteria-free root canal system before permanent root filling in order to achieve optimal healing conditions for the periapical tissues.     

感染根管优势菌致病能力的实验研究

目的研究感染根管优势菌在根尖周炎发病过程中的作用,探讨不同细菌致病能力的差异。方法选择牙髓卟啉单胞菌（Porphyromonas endodontalis,P．e）、牙龈卟啉单胞菌（Porphyromonas gingivalis,P．g）、具核梭杆菌（Fusobacterium nucleatum,Pn）分别接种于SD大鼠第一磨牙髓腔内,以生理盐水和髓腔开放作为对照。术后1、2、4、8周处死大鼠,取上、下颌骨拍摄X线片,测量并比较各组第一磨牙根尖周透射影面积;组织学切片观察各组根尖周组织病理变化,评价根尖周组织炎症程度。结果X线片测量结果显示根尖阴影面积在术后8周最大,组织学评价结果为术后4周根尖周炎症程度最重,骨吸收最为活跃。各观察阶段,Pg、P．e组X线片和组织学评价结果均与生理盐水组无统计差异（P〉0．05）;术后4周,F．n组x线片和组织学评价结果与Pe组、P．g组及生理盐水对照组有显著差异（P〈0.01）,前者骨吸收面积和炎症程度均高于后者;但在所有组中,髓腔开放组根尖周炎症程度最重（P〈0．01）。结论P．g或P．e单独感染牙髓,导致根尖周炎发病能力较弱,Fn相对较强。多种细菌混合感染是根尖周炎形成、发展的主要原因。     

Radiographic analysis of the development of periapical lesions in normal rats, sialoadenectomized rats and sialoadenectomized-immunosuppressed rats

Abstract – The purpose of this study was to investigate and to compare radiographically the development of periapical lesions in the lower left first molar of normal rats, sialoadenectomised rats and sialoadenectomised-immunosuppressed rats. Sixty male Wistar rats, weighing from 170 to 200 g were utilized. The animals were divided equally into three groups: group I – 20 normal rats; group II – 20 sialoadenectomised rats; and group III – 20 sialoadenectomised-immunosuppressed rats. Groups II and III were sialoadenectomized using the modified Cheyne technique. After 2 weeks, group III was submitted to a immunosuppression regimen by daily subcutaneous cyclosporin A injection (10 mg/kg body weight). After 1 week of immunosuppression for this group, the pulps of all the animals (group I, II and III) were exposed to the oral cavity, to produce apical periodontitis. Five animals of each group were killed 7, 14, 21 and 28 days after pulpal exposure. Their mandibles were surgically removed and radiographically analysed. The lesions were measured using 'Global Lab Image' software. The results showed predictable growth of the lesions during the experimental period. No significant difference was observed between the groups. It was concluded that possible changes in the oral flora and in the host immune response due to xerostomia associated or not to the immunosuppression did not alter the development of the periapical lesions in rats.     

Apical periodontitis development and bacterial response to endodontic treatment. Experimental root canal infections in monkeys with selected bacterial strains

In six monkeys, 160 root canals were inoculated with a combination of four bacterial strains belonging to species Streptococcus milleri, Peptostreptococcus anaerobius, Prevotella oralis, and Fusobacterium nucleatum. In two other monkeys, 24 root canals were inoculated with a five-strain combination consisting of these strains and a strain of Enterococcus faecalis. All strains were previously isolated from an infected monkey root canal. After 8-12 months, survival of the strains was recorded bacteriologically, and the reaction in the periapical region was radiographed. From 180 of 184 root canals, one or more of the bacterial strains were reisolated. The two facultative strains were more frequently reisolated than the anaerobic strains. Apical periodontitis was registered in the periapical region of more than 96% of root canals with reisolated bacteria but in none of those without reisolated bacteria. Endodontic treatment was carried out in two sessions with an interval of 14 d without interappointment dressings, and the effect was evaluated bacteriologically before and after each treatment. The chemo-mechanical treatment reduced significantly the number of strains and bacterial cells. The facultative bacteria were more resistant to the treatment than the anaerobic bacteria. The five-strain combination had a higher survival rate than the four-strain combination.     

Persistent extraradicular infection in root-filled asymptomatic human tooth: scanning electron microscopic analysis and microbial investigation after apical microsurgery

Introduction

Procedural accidents have a negative effect on healing and might contribute to the persistence of infections in inaccessible apical areas, requiring surgical intervention. This report describes a case of persistent apical periodontitis of a lower left first molar associated with the sinus tract and a periapical lesion that required nonsurgical endodontic retreatment and apical surgery for resolution.

Methods

The tooth had received endodontic treatment 3 years ago and had to be retreated using the crown-down technique with chemical auxiliary substance (2% chlorhexidine gel), foramen patency, and enlargement and was filled in a single appointment. The occlusal access cavity was immediately restored with composite resin. After 1 month, it could be observed that the sinus tract persisted and, radiographically, the lesion remained unaltered. Therefore, endodontic microsurgery was indicated. Apical microsurgery was performed under magnification with the use of a dental operating microscope including apicectomy, root end with ultrasound, and sealing with mineral trioxide aggregate. A microbiological sample was collected from the apical lesion. The resected distal root apex was observed by scanning electron microscopy.

Results

The following species were detected: Actinomyces naeslundii and Actinomyces meyeri, Propionibacterium propionicum, Clostridium botullinum, Parvimonas micra, and Bacteroides ureolyticus; scanning electron microscopic analysis revealed bacterial biofilm surrounding the apical foramen and external radicular surface. Gutta-percha overfilling at the apex because of a zip caused during initial endodontic treatment could be observed. A 6-month follow-up showed apparent radiographic periapical healing, which progressed after 24 months.

Conclusion

Gram-positive anaerobic bacteria and extraradicular biofilm seem to participate in the maintenance of persistent periapical pathology, and endodontic retreatment followed by periapical microsurgery proved to be a successful alternative in the resolution of persistent extraradicular infections.     

Infection in a Complex Network of Apical Ramifications as the Cause of Persistent Apical Periodontitis: A Case Report

Introduction

This article reports a case of persistent apical periodontitis lesion in a mesiobuccal root of a maxillary molar subjected to single-visit endodontic treatment.

Methods

The treatment protocol followed endodontic standards including using nickel-titanium instruments with working length ending 0.5-mm short of the apex, establishment and maintenance of apical foramen patency, irrigation with 5% NaOCl, smear layer removal, a final rinse with and ultrasonic agitation of chlorhexidine, and filling by the vertical compaction technique. Even so, the lesion in the mesiobuccal root became larger in size after follow-up examination at 1 year 6 months, and periradicular surgery was performed. Radiographic control after 11 months showed that periradicular healing was almost complete. The root apex and the lesion were analyzed histologically and histobacteriologically.

Results

The lesion was diagnosed as a “pocket cyst,” and no bacteria were noted extraradicularly. The cause of continued disease was a heavy bacterial biofilm infection located in an intricate network of apical ramifications. Bacteria were also observed on the walls of one of the mesiobuccal canals packed between the obturation material and the root canal wall.

Conclusions

This case report reinforces the need for treating the infected root canal as a complex system that possesses anatomic intricacies in which bacteria can spread and remain unaffected by treatment procedures.     

Longitudinal study of periapical and endodontic status in a Danish population

AIM: To describe and discuss changes in periapical and endodontic status in a general Danish population. METHODOLOGY: In 1997, 616 randomly selected individuals had a full-mouth radiographic survey taken. In 2003, 77% of the participants attended for a new full-mouth radiographic examination. Information on endodontic treatment and periapical status was obtained. The periapical index (PAI) was used to assess apical periodontitis (AP). RESULTS: More participants had root filling(s) and AP in 2003 than in 1997. More teeth had AP and/or root fillings in 2003. Fewer of the root-filled teeth (RFT) had AP in 2003. Less than 3% of the teeth without root fillings (NRFT) that in 1997 had no AP, developed AP and/or received a root filling. Of the NRFT which in 1997 had AP, more than 35% still had AP and no root filling in 2003. Approximately, 30% of the NRFT with AP in 1997 received a root filling. Of the teeth that received a root filling, 40% had healed, whereas 60% had not. Approximately, 25% of the NRFT that in 1997 had AP had been extracted. In 1997 there were 618 RFT, 314 of the RFT had no AP in 1997. Almost 20% of the RFT that in 1997 were periapically sound, developed AP. Of the 304 RFT with AP in 1997, approximately 30% had healed, in 60% AP persisted, and 10% were extracted. CONCLUSIONS: The present study indicates that caution must be exercised when statements on the outcome of root canal treatment are made based on the cross-sectional studies.     

Cross-sectional evaluation of the periapical status and quality of root canal treatment in a selected population of urban Turkish adults

AIM: To investigate the prevalence of apical periodontitis and the quality of root canal treatment in an adult Turkish population who visited a university dental clinic. SUMMARY: The periapical status of 8863 teeth belonging to 375 patients was evaluated by two pre-calibrated observers from panoramic radiographs. The presence of apical periodontitis, and the prevalence and quality of root fillings were recorded. The relationship between the radiographic quality of root fillings and apical periodontitis was examined by chi-squared statistical-analysis. Of 8863 teeth, 470 (5.3%) had undergone root canal treatment. Forty-seven per cent of all the subjects had at least one root-filled tooth. Periapical radiolucencies were visible on 4.2% of teeth examined, with 53.5% of root-filled teeth presenting apical periodontitis. Ninety-one per cent of root-filled teeth with periapical pathosis were determined to have inadequate root fillings. A statistically significant correlation was found between the quality of root fillings and the presence of apical periodontitis (P < 0.05). KEY LEARNING POINTS: The radiographic quality of root fillings correlated with periapical radiographic signs of pathosis in a selected population of Turkish adults. There is a need to improve the standards of root canal treatment in the study population.     

Reaction of inflamed periapical tissue to intracanal medicaments and root canal sealers

Abstract The effects of different intracanal medicaments and zinc oxide-eugenol based root canal sealers on an experimentally induced apical periodontitis were studied histologically in mesial roots of lower molars of Wistar rats. After root canal instrumentation each canal was filled either with an intracanal medicament twice for 3 days each time or with a sealer for 21 days. The intracanal medicament chlorophenol caused periapical tissue damage. P-chloroxylenol-camphor lead to periapical improvement as did 5% sodium-hypochlorite. 12% sodium-hypochlorite gave tissue damage. After intracanal medication with an aqueous suspension of calcium hydroxide periapical repair was clearly visible. A combination of a corticoid and an antibiotic appeared to induce damage of the periapical tissues. The root canal sealers Endomethasone and N2 essentially impaired periapical repair. The results were acceptable for Aptal-Zink-Harz root canal fillings after 21 days as well as after 56 days.     

Recurrent Apical Periodontitis and Late Endodontic Treatment Failure Related to Coronal Leakage: A Case Report

Introduction

This article describes a case of late failure after endodontic retreatment as characterized by recurrent post-treatment apical periodontitis.

Methods

At the time of the initial treatment, the patient presented with acute apical abscess associated with a tooth with pulp necrosis caused by trauma. Four years later, the tooth was retreated because of persistent disease. The follow-up examination 28 months after retreatment showed complete healing.

Results

The patient returned 11 years and 7 months later for bleaching of the discolored tooth, and although the periodontal tissues were clinically and radiographically normal, a fracture line was observed on the mesial aspect of the pulp chamber. Extraction was indicated, but the patient only returned 5 years and 9 months later. Then a radiograph showed recurrent post-treatment apical periodontitis. The tooth was extracted, and histopathologic and histobacteriologic analyses revealed bacterial colonies along the fracture line and colonizing ramifications and accessory canals at the apical root canal system.

Conclusions

Coronal leakage can be regarded as the most reasonable explanation for resurgence of the disease. However, a predisposing overlapping condition in the form of root fracture conceivably favored the penetration of bacteria from saliva and plaque biofilm along the filled root canal.     

The periapical index: A scoring system for radiographic assessment of apical periodontitis

Abstract A scoring system for registration of apical periodontitis in radiographs is presented. The system is termed the periapical index (PAI) and provides an ordinal scale of 5 scores ranging from 1 (healthy) to 5 (severe periodontitis with exacerbating features). Its validity is based on the use of reference radiographs of teeth with verified histological diagnoses. Results from studies involving 11 observers and 47 selected radiographs document that the PAI system is reasonably accurate, reproducible and able to discriminate between sub-populations. It may also allow for results from different researchers to be compared. The system may be suitable for the analysis of periapical radiographs in epidemiological studies, in clinical trials and in retrospective analyses of treatment results in endodontics.     

Electrophoresis of whole-cell soluble proteins of microorganisms isolated from bacteremias in endodontic therapy

We have previously demonstrated that anaerobic bacteria are the microorganisms most frequently isolated from blood following endodontic therapy of teeth with apical periodontitis. Phenotypic characterisation of the isolates suggested that the bacteria in the blood originated from the root canal. The present experiment using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was carried out in an effort to verify these findings, and to further study the microorganisms involved in endodontic bacteremias. Soluble cellular proteins were extracted from 11 reference strains and 26 bacterial isolates recovered from the root canal and blood. These included Propionibacterium acnes, Peptostreptococcus prevotii, Fusobacterium nucleatum, Prevotella intermedia, Actinomyces israelii, Streptococcus intermedius, Streptococcus sanguis. The electrophoretic patterns mostly confirmed the identity of the isolates as determined by the biochemical and antimicrobial resistance tests. Furthermore, with this typing method the species Prevotella intermedia and Prevotella nigrescens could be differentiated. These species had been recovered from both root canal and blood. Also, differences between subspecies of Fusobacterium nucleatum became evident with SDS-PAGE, and the results indicated that the organism recovered from the root canal and blood was Fusobacterium nucleatum subsp. vincentii. The electrophoretic patterns of the different organisms isolated from the root canal and the blood were similar, providing further evidence that the bacteria found in the blood originated from the root canal.     

Influence of coronal restorations on the periapical health of endodontically treated teeth

Abstract – The purpose of the study was to evaluate a possible relationship between the quality of the coronal restoration, the root canal obturation and the periapical status of endodontically treated teeth. Full mouth series of radiographs from randomly selected patient charts at the Dental Faculty, University of Oslo were examined. A total of 1001 endodontically treated teeth restored with a permanent restoration were evaluated independently by two examiners. According to a predetermined set of radiographic criteria, the technical quality of the root filling of each tooth was scored as either good (GE) or poor (PE), and the technical quality of the coronal restoration was scored as good (GR) or poor (PR). The root and the surrounding structures were then evaluated and according to the periradicular findings, the treatment was categorized as success or failure. The success rate for all endodontically treated teeth was 67.4% ( n =1001). Teeth with root canal posts had a success rate of 70.7% ( n =527) and teeth without posts had a success rate of 63.6% ( n =472). The two groups with technically good endodontics had the highest success rates. In combination with technically good restorations the success rate was 81% (GE+GR, 81%) and combined with technically poor restorations the success rate was 71% (GE+PR, 71%). The two groups with technically poor endodontics combined with either good restorations or poor restorations had significantly lower success rates (PE+GR, 56% and PE+PR, 57%). The technical quality of the endodontic treatment as judged radiographically was significantly more important than the technical quality of the coronal restoration when the periapical status of endodontically treated teeth was evaluated.     

Healing of periapical lesions of pulpless teeth after endodontic treatment with controlled asepsis

Abstract Using a careful anaerobic bacteriological technique, bacteria were shown to be eliminated from infected root canals before the endodontic treatment was finished by root filling. Healing of the periapical lesions of the teeth was followed for 2–5 yr. The majority of the 79 lesions healed completely or decreased in size in such a way that they could be expected to heal. In 5 cases there was no or only an insignificant decrease in the size of the lesions. Two of these lesions were shown to contain bacteria of the species Actinomyces or Arachnid. In another case there were dentin chips in the periapical tissue. Periapical lesions which fail to heal in spite of careful bacteriological monitoring of the endodontic treatment may in some cases be due to an establishment of the bacteria outside the root canal in the periapical tissue. In these sites, the bacteria are inaccessible to conventional endodontic treatment.     

New Bacterial Composition in Primary and Persistent/Secondary Endodontic Infections with Respect to Clinical and Radiographic Findings

Introduction

The aim of the present study was to analyze the microbiota of primary and secondary/persistent endodontic infections of patients undergoing endodontic treatment with respect to clinical and radiographic findings.

Methods

Samples from the root canals of 21 German patients were taken using 3 sequential sterile paper points. In the case of a root canal filling, gutta-percha was removed with sterile files, and samples were taken using sterile paper points. The samples were plated, and microorganisms were then isolated and identified morphologically by biochemical analysis and sequencing the 16S rRNA genes of isolated microorganisms.

Results

In 12 of 21 root canals, 33 different species could be isolated. Six (50%) of the cases with isolated microorganisms were primary, and 6 (50%) cases were endodontic infections associated with root-filled teeth. Twelve of the isolated species were facultative anaerobic and 21 obligate anaerobic. Monomicrobial infections were found for Enterococcus faecalis and Actinomyces viscosus. E. faecalis was most frequently isolated in secondary endodontic infections (33%). Moraxella osloensis was isolated from a secondary endodontic infection that had an insufficient root canal filling accompanied by a mild sensation of pain. A new bacterial composition compromising Atopobium rimae, Anaerococcus prevotii, Pseudoramibacter alactolyticus, Dialister invisus, and Fusobacterium nucleatum was recovered from teeth with chronic apical abscesses.

Conclusions

New bacterial combinations were found and correlated to clinical and radiographic findings, particularly to chronic apical abscesses. M. osloensis was detected in root canals for the second time and only in German patients.     

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.     

Clinical performance of three endodontic sealers

Abstract The clinical performance of three endodontic sealers, AH 26®, Kloroperka N-Ø® and ProcoSol®, was assessed in a prospective study of endodontic treatment in 810 roots. The roots were treated by undergraduate students according to a standardized procedure, and were filled with laterally condensed gutta-percha and sealer. The sealer was randomly selected just prior to filling. The patients were recalled yearly for 4 years for a clinical and radiographic control examination, and the radiographs were scored using the periapical index (PAI) scoring system. Ridit analysis provided optimal discrimination between subgroups of roots with regard to the radiographic status of the periapical tissues as a measure of the clinical performance of the materials. The periapical status of roots filled with AH 26® or ProcoSol® was better than that of roots filled with Kloroperka®. The difference was significant after 1 year and persisted through the 4-year observation period. The difference was also evident after stratification of the material with regard to preoperative pulpal and periapical diagnoses. It is concluded that the choice of sealer may influence the outcome of endodontic treatment, and that the perapical index is a useful discriminatory tool for assessment of treatment results in endodontics.