Bacteriologic evaluation of the efficacy of mechanical root canal instrumentation in endodontic therapy

The presence of bacteria in 17 single-rooted teeth, with periapical lesions, was studied throughout a whole period of treatment. The root canals were irrigated with physiologic saline solution during instrumentation. No antibacterial solutions or dressings were used. Bacteria were found in all initial specimens from the teeth (median number of bacterial cells 4 x 10(5), range 10(2) - 10(7)) and the number of strains in the specimens ranged from 1 to 10.88% of the strains were anaerobic. The most commonly isolated species were: Peptostreptococcus micros, Peptostreptococcus anaerobius, Fusobacterium nucleatum, Bacteroides oralis, Bacteroides melaninogenicus subsp intermedius and Eubacterium alactolyticum. Mechanical instrumentation reduced the number of bacteria considerably. Specimens taken at the beginning of each appointment usually contained 10(4) - 10(6) bacterial cells and at the end 10(2) - 10(3) fewer. Bacteria were eliminated from the root canals of eight teeth during the treatment. In seven root canals bacteria persisted despite treatment on five successive occasions. There was no evidence that specific microorganisms were implicated in these persistent infections. Teeth where the infection persisted despite being treated five times were those with a high number of bacteria in the initial sample.     

Bacteriologic evaluation of the efficacy of mechanical root canal instrumentation in endodontic therapy

Abstract – The presence of bacteria in 15 single-rooted teeth, with periapical lesions, was studied throughout a whole period of treatment. The root canals were irrigated with physiologic saline solution during instrumentation. No antibacterial solutions or dressigs were used. Bacteria were found in all irnitial specimens form the teeth (median numver of bacterial cell 4x10⁵; range 10²-10⁷) and the number of strains in the specimens ranged from 1 to 10.88% of the strains were anaerobic. The most commonly isolated species were: Peptostreptococcus micros, Peptostrcptococcus anacrobius, Fusobacterium nucleatum, Bacteroides oralis, Bacteroides melaninogenicus subsp. intermedius and Eubacterium alactolyticum. Mechanical instrumentation reduced the number of bacteria considerably. Specimens taken at the beginning of each appointment usually contained 10⁴-10⁶ bacterial cells and at the end 10²-10³fewer. Bacteria were eliminated from the root canals of eight teeth during the treatment. In seven root canals bacteria presisted despite treatment on five successive occasions. There was no evidence that specific microorganisms were implicated in these persistent infections. Teeth where the infection persisted despite being treated five times were those with a hig number of bacteria in the initial sample.     

Selected endodontic pathogens in the apical third of infected root canals: a molecular investigation

Bacteria located at the apical portion of the root canals are conceivably in a strategic position to induce damage to the periradicular tissues and resulting inflammatory diseases. This study sought to investigate the prevalence of 11 selected putative endodontic pathogens in the apical third of infected root canals associated with periradicular lesions. The apical root portion of 23 extracted teeth with carious pulpal exposures and attached periradicular lesions was sectioned, and the root canals were sampled for microbiological investigation. DNA was extracted from the samples and analyzed for the presence of 11 bacterial species using a nested polymerase chain reaction assay. The results showed that Pseuramibacter alactolyticus occurred in 10 cases (44%), Treponema denticola in 6 (26%), Fusobacterium nucleatum in 6 (26%), Porphyromonas endodontalis in 4 (17%), Filifactor alocis in 2 (9%), Dialister pneumosintes in 1 (4%), Porphyromonas gingivalis in 1 (4%), and Tannerella forsythensis in 1 (4%). No sample yielded Prevotella intermedia, Prevotella nigrescens, or Campylobacter rectus. Of the samples examined, 17 were positive for at least 1 of the target species. Occurrence of these bacterial species in the apical third of infected root canals suggests that they can be involved in causation of periradicular lesions.     

不同类型感染根管内4种厌氧菌定植状况分析

目的　应用16S rDNA-PCR技术检测不同类型感染根管内4种厌氧菌的定植状况。方法　于南京大学医学院附属口腔医院收集临床上拔除的新鲜离体牙30颗,分为3组：牙髓炎组、根尖周炎组、根管治疗失败组,每组10颗。将各组牙齿的根管分为根管冠中段（离根尖6 mm）和根管尖段（离根尖3 mm）,提取每个根管段的细菌基因组DNA,用PCR扩增细菌16S rDNA基因片段的方法检测细菌种类,计算检出率并进行统计学分析。结果　在牙髓炎组,根管冠中段能检测到牙髓卟啉单胞菌（P.endodontalis, P.e）、具核梭杆菌（F.nucleatum,F.n）、粪肠球菌（E.faecalis,E.f）和中间普氏菌（P.intermedia,P.i）,其中P.e的检出率最高（P < 0.05）,根管尖段只检测到P.e的存在。在根尖周炎组,4种厌氧菌（P.e、F.n、E.f、P.i）在根管冠中段和尖段的检出率差异无统计学意义（P > 0.05）。在根管治疗失败组,E.f在根管尖段的检出率（60%）比在根管冠中段的检出率（10%）高,差异有统计学意义（P < 0.05）。结论　牙髓炎的根管细菌主要定植在冠中段,P.e检出率最高;根尖周炎的根管冠中段和根管尖段4种细菌检出率无明显差别,都是以P.i为主;根管治疗失败的根管细菌以E.f为主,主要集中于根管尖段。     

Influence of combinations of oral bacteria on periapical tissues of monkeys

Abstract – The present study deals with the ability of 11 bacterial strains, in various combinations, to induce periapical reactions. The indigenous oral bacteria were originally isolated from an experimental apical periodontitis in monkey. Eight of the strains were a complete collection isolated from one root canal. These strains were inoculated together, in equal proportions, into 12 root canals. In addition, 63 canals were inoculated with other combinations or separate strains. At the end of the experimental period it was found that in the mixed infections the Bacteroides oralis strain predominated in most root canals. In contrast, this Bacteroides strain was not reisolated in any of nine root canals when inoculated in a pure culmfe. Enterococci, however, survived as pure cultures in all canals. The mixed infections showed the greatest capacity ofindticing apical periodontitis, as revealed by radiography, and most pronounced was the "eight-strain collection". The facultatively anaerobic streptococci induced only weak periapical reactions.     

根尖周炎厌氧菌培养结果分析

对４６例根尖周炎患者牙根管内厌氧菌分离培养，结果分离出厌氧菌共１３９株，其中急性根尖周炎９５株，慢性根尖周炎４４株，厌氧菌分离率为９６％，检出率较高的厌氧为梭杆菌属、消化链球菌属、丙酸杆菌属、拟杆菌属、卟啉菌属、普里沃菌属     

Influence of the enlargement of the apical foramen in periapical repair of contaminated teeth of dog

Root canals of dogs' premolar teeth were exposed to contamination and to the development of periapical inflammation over a period of 45 days. Root canals were overinstrumented 2 mm beyond the apical foramen with file No. 60 and were underfilled by 2 to 3 mm short of the roentgenographic apex. Ninety days after endodontic treatment, healing and ingrowth of connective tissue into the root canal occurred in 67.8% of the cases. These results suggest that the diameter of the apical foramen and the intensity of the canal contamination are determining factors for periapical tissue repair in cases of pulpal necrosis.     

The antibacterial effect of camphorated paramonochlorophenol, camphorated phenol and calcium hydroxide in the treatment of infected root canals

Abstract The bactericidal efficacy of calcium hydroxide, camphorated phenol and camphorated paramonochlorophenol as intracanal dressings was evaluated clinically when the root canals of 65 single-rooted teeth with periapical lesions were treated. A bacteriological technique that could detect even small numbers of anaerobic bacteria in the canals was used. After treatment, including intracanal dressing with calcium hydroxide paste (Calasept), bacteria were recovered from one of 35 treated root canals. After use of camphorated phenol or camphorated paramonochlorophenol as the dressing, bacteria were recovered from 10 of 30 treated root canals. The isolated bacteria were predominantly Gram-positive and anaerobic. There was no indication that specific bacteria were resistant to the treatment. The results indicate that the endodontic treatment of infected root canals can be completed in two appointments when calcium hydroxide paste is used as an intracanal dressing.     

长春地区儿童乳牙急慢性根尖周炎根管内厌氧菌的分析

目的 对长春地区60例儿童急慢性根尖周炎患者的感染根管进行厌氧菌分离鉴定，为指导临床选择用药奠定基础。方法 利用智能化细菌鉴定和药敏系统-ATB快速鉴定仪分离培养和鉴定细菌。结果 98．3％（59／60）的患牙共检出厌氧菌144株，平均每例标本检出2．44株。结论 乳牙急性根尖周炎感染根管内的优势菌以梭杆菌为主，慢性根尖周炎感染根管内的优势菌以放线菌为主。     

Prevalence of black-pigmented bacteroides species in root canal infections

The prevalence of black-pigmented Bacteroides species in the root canals of 72 teeth with apical periodontitis was evaluated. Twenty-two of the canals contained one or more species of black-pigmented Bacteroides. Bacteroides intermedius (14 strains) and Bacteroides endodontalis (5 strains) were most common. Of the species Bacteroides gingivalis, Bacteroides loeschei, and Bacteroides denticola, 2, 3, and 1 strains, respectively, were isolated. The median number of bacterial cells recovered from the root canals containing black-pigmented Bacteroides was 2.8 x 10(5) and from the other canals 3.0 x 10(3). The mean number of strains was 7.9 and 3.3, respectively. Sixteen of the 22 root canals containing black-pigmented Bacteroides species were associated with acute apical abscesses and purulent drainage through the root canal. The other six teeth with black-pigmented Bacteroides were asymptomatic. One additional abscess was present among the 72 cases. This root canal contained Actinomyces israelii and Actinomyces naeslundii.     

Influence of infection at the time of root filling on the outcome of endodontic treatment of teeth with apical periodontitis

This study investigated the role of infection on the prognosis of endodontic therapy by following-up teeth that had had their canals cleaned and obturated during a single appointment. The root canals of 55 single-rooted teeth with apical periodontitis were thoroughly instrumented and irrigated with sodium hypochlorite solution. Using advanced anaerobic bacteriological techniques, post-instrumentation samples were taken and the teeth were then root-filled during the same appointment. All teeth were initially infected; after instrumentation low numbers of bacteria were detected in 22 of 55 root canals. Periapical healing was followed-up for 5 years. Complete periapical healing occurred in 94% of cases that yielded a negative culture. Where the samples were positive prior to root filling, the success rate of treatment was just 68%— a statistically significant difference. Further investigation of three failures revealed the presence of Actinomyces species in each case; no other specific bacteria were implicated in failure cases. These findings emphasize the importance of completely eliminating bacteria from the root canal system before obturation. This objective cannot be reliably achieved in a one-visit treatment because it is not possible to eradicate all infection from the root canal without the support of an inter-appointment antimicrobial dressing.     

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.     

Clinical efficacy of an endodontic antiseptic in a controlled release delivery system

Abstract The purpose of this clinical study was to assess the bacteriological status of the root canal after disinfection with a quaternary ammonium compound in a controlled release delivery system. Fifty-three teeth with apical periodontitis as evidenced by periapical radiolucencies were used. Under aseptic conditions the root canals were completely instrumented and irrigated with sodium hypochlorite. After the instrumentation, 38 teeth were treated with the quaternary ammonium compound in the controlled release dispenser; 15 teeth were treated with formocresol. Bacteriological samples from the root canals were taken after 7 days using an anaerobic technique. The results indicated that the quaternary ammonium compound in controlled release was as effective as formocresol in obtaining bacteria-free root canals. The advantages of an antiseptic with a long lasting effect for the elimination of bacteria from the root canal and for the prevention of reinfection were emphasized.     

Profiling of Propionibacterium acnes recovered from root canal and blood during and after endodontic treatment.

This report describes the first results of an ongoing study of bacteremia after endodontic treatment of teeth with Asymptomatic apical periodontitis. After access cavity preparation, microbiological samples were taken from the root canal under aseptic conditions in 4 single-rooted teeth in 4 patients. In treatment of 2 of the patients, the first 3 reamers (sizes 15-25) were deliberately used to a level 2 mm beyond the apical foramen. In 2 patients the instrumentation ended inside the root canal 1 mm short of the apical foramen. Blood samples were taken from the patients during the endodontic instrumentation and 10 min after the treatment was completed. Using lysis-filtration under anaerobic conditions, the blood was passed through a cellulose membrane filter. The filters as well as the root canal samples were incubated using an anaerobic technique. Anaerobic bacteria were isolated from all root canals. In the 2 patients where overinstrumentation had occurred, Propionibacterium acnes was recovered both from the root canals and from the blood samples taken during and after the treatment had been completed. Biochemical profiles, antibiotic susceptibility tests and electrophoresis of soluble proteins revealed that Propionibacterium acnes isolated from the root canal and blood samples were identical within patients, but varied between patients. Facultative anaerobic bacteria including Streptococcus sanguis were recovered from only one root canal sample and not from the blood samples.     

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.     

Antibacterial activity of 2% chlorhexidine gluconate and 5.25% sodium hypochlorite in infected root canal: in vivo study

In this study, the antibacterial activity of the different antibacterial solutions using as root canal irrigant was compared in the teeth with pulpal necrosis and with periapical pathosis. Thirty root canals of incisors and premolars of 20 patients were used. Before and after the root canal preparation, two canal samples were obtained by a harvesting method using a sterile paper point in the first appointment. During the biomechanical preparation, both irrigant solutions were used for each tooth which were randomly divided into two groups. Last samples were also obtained before the root filling procedure. Samples obtained from the root canals were subjected to microbiologic processing, including anaerobic incubation on trypticase soy agar for 5 to 7 days. After counting of CFU on the plates, we concluded that both chlorhexidine gluconate and sodium hypochlorite were significantly effective to reduce the microorganisms in the teeth with necrotic pulp, periapical pathologies, or both, and could be used successfully as an irrigant solution.     

Microbiological analysis of infected root canals from symptomatic and asymptomatic teeth with periapical periodontitis and the antimicrobial susceptibility of some isolated anaerobic bacteria

The purpose of the present study was to investigate the correlation between the composition of the bacterial flora isolated from infected root canals of teeth with apical periodontitis with the presence of clinical signs and symptoms, and to test the antibiotic susceptibility of five anaerobic bacteria mostly commonly found in the root canals of symptomatic teeth against various substances using the E-test. Microbial samples were taken from 48 root canals, 29 symptomatic and 19 asymptomatic, using adequate techniques. A total of 218 cultivable isolates were recovered from 48 different microbial species and 19 different genera. Root canals from symptomatic teeth harbored more obligate anaerobes and a bigger number of bacterial species than the asymptomatic teeth. More than 70% of the bacterial isolates were strict anaerobes. Statistical analysis used a Pearson Chi-squared test or a one-sided Fisher's Exact test as appropriate. Suggested relationships were found between specific microorganisms, especially gram-negative anaerobes, and the presence of spontaneous or previous pain, tenderness to percussion, pain on palpation and swelling amoxicillin, amoxicillin + clavulanate and cephaclor were effective against all the strains tested. The lowest susceptibility rate was presented by Prevotella intermedia/nigrescens against Penicillin G. Our results suggested that specific bacteria are associated with endodontic symptoms of infected teeth with periapical periodontitis and the majority of the anaerobic bacterial species tested were susceptible to all antibiotics studied.     

Importance of bacterial endotoxin (LPS) in endodontics

New knowledge of the structure and biological activity of endotoxins (LPS) has revolutionized concepts concerning their mechanisms of action and forms of inactivation. Since the 1980's, technological advances in microbiological culture and identification have shown that anaerobic microorganisms, especially Gram-negative, predominate in root canals of teeth with pulp necrosis and radiographically visible chronic periapical lesions. Gram-negative bacteria not only have different factors of virulence and generate sub-products that are toxic to apical and periapical tissues, as also contain endotoxin (LPS) on their cell wall. This is especially important because endotoxin is released during multiplication or bacterial death, causing a series of biological effects that lead to an inflammatory reaction and resorption of mineralized tissues. Thus, due to the role of endotoxin in the pathogenesis of periapical lesions, we reviewed the literature concerning the biological activity of endotoxin and the relevance of its inactivation during treatment of teeth with pulp necrosis and chronic periapical lesion.     

Predominant obligate anaerobes invading the deep layers of root canal dentine

This study was carried out to investigate the presence and types of bacteria invading the deep layers (0.5-2.0 mm from the surface of the root canal wall) of infected dentine of human root canals by sampling with an anaerobic glove box system the split surfaces of eight freshly extracted teeth. More bacteria were recovered after incubation in an anaerobic glove box than after aerobic incubation in air with 30 per cent CO2. Out of 256 predominant bacterial isolated, 205 isolates (80 per cent) were obligate anaerobes. These findings suggest that the environment of deep layers of endodontic dentinal lesions is anaerobic and favours the growth of anaerobes. Among the obligate anaerobic isolates, strains belonging to Lactobacillus (30 per cent) and Streptococcus (13 per cent) were predominant, followed by Propionibacterium (9 per cent). No strains of obligate anaerobic Gram-negative rods were isolated. The microflora of deep layers of infected root dentine is somewhat similar to that of the deep layers of carious lesions in coronal dentine.     

乳牙感染根管的菌丛分析

目的分析乳牙根尖周炎感染根管菌丛，为进一步防治提供依据。方法用直接酶法对８例乳牙急性根尖周炎、１４例乳牙慢性根尖周炎感染根管菌丛成分进行分析。结果共检出２４０株细菌，厌氧菌２００株，主要分布于消化链球菌、类杆菌、韦永氏菌、真细菌、丙酸杆菌、放线菌和梭杆菌。急性炎症组类杆菌、梭杆菌的检出率明显高于慢性组（Ｐ＜００５），主要差异在牙龈类杆菌和具核梭杆菌；慢性炎症组小韦永氏菌的检出率明显高于急性组（Ｐ＜０．０５）。结论乳牙急、慢性根尖周炎感染根管内是以厌氧菌为优势菌的混合感染。牙龈类杆菌、具核梭杆菌可能与乳牙根尖周炎的急性症状有关。小韦永氏菌在乳牙慢性根尖周炎中的作用不容忽视