Microbial flora of sinus tracts and root canals of non-vital teeth

Abstract The occurrence of bacteria in 12 endodontically induced periodontal lesions associated with sinus tracts was examined. The microbial flora encountered in the sinus tract was compared with that of the root canal of the involved teeth which had not experienced any prior endodontic therapy. All microbiological samples taken from the sinus tract and from the root canal system contained bacteria. Seventy-one strains were detected in the extraradicular lesions. Of the anaerobic species, Fusobacterium nucleatum (7 strains), Prevotella intermedia (4 strains) and P. oralis (4 strains) were most frequently found. In the group of the facultative anaerobes Streptococcus spp. were predominant. Ninety-four strains were isolated from the root canal system of the 12 teeth. P. intermedia (6 strains), P. buccae (5 strains), F. nucleatum (5 strains) and Lactobacillus plantarum (5 strains) were most common. In 9 cases, species present in the root canal could be revealed in the extraradicular lesions. It was concluded that a variety of microorganisms were capable of colonizing endodontically induced, extraradicular lesions clinically characterized by sinus tracts.     

Developmental disturbances in permanent teeth after intrusion of their primary predecessors

abstract — The frequency and type of developmental disturbances in the permanent teeth in relation to the child's age at the time of injury were examined in 78 patients with 100 intruded primary incisors. The central incisors were found to be the most frequently affected teeth. Only maxillary teeth were involved. The dominating age group was 1–3 years and intrusion was seldom seen after the age of 4 years. The frequency of disturbed normal development of the permanent teeth was 54%. In eight cases the intruded teeth were removed immediately, 86 teeth reerupted, and six teeth did not reerupt. Internal white enamel hypoplasia was seen frequently; external hypoplasia, seldom.     

Detection of bacteria in endodontic samples by polymerase chain reaction assays and association with defined clinical signs in Italian patients

BACKGROUND/AIMS: The presence of selected bacteria (Enterococcus faecalis, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythensis, Treponema denticola) in infected root canals was studied using polymerase chain reaction (PCR) assays, and the association of bacteria with clinical signs of endodontic disease was assessed. The null hypothesis, that no difference could be observed between clinical signs of apical periodontitis and a specific bacterial strain, was tested. METHODS: Microbial samples were obtained from 62 teeth in 54 patients with endodontic disease. For each tooth, clinical data including patient symptoms were collected. Teeth were categorized by diagnosis as having acute apical periodontitis (AAP, teeth with clinical symptoms but no periapical radiolucency, n=22), chronic apical periodontitis (CAP, teeth with radiolucency but no clinical symptoms, n=15) or exacerbated apical periodontitis (EAP, teeth with symptoms and radiolucency, n=25). Seventy-one percent of cases were primary endodontic infections, and 29% were recurrent ('secondary') endodontic infections (failing cases). PCR assays were used to detect the presence of the selected bacteria. RESULTS: T. denticola and E. faecalis were each detected in 15 of 62 samples (24%), P. gingivalis in 8 samples (13%), P. intermedia in 5 samples (8%), and T. forsythensis in 4 samples (7%). T. denticola was detected in 56% of teeth with EAP. E. faecalis was found in 60% of teeth with CAP and in 72% of teeth with secondary infection. Statistical analysis demonstrated an association of CAP and secondary endodontic infection with the presence of E. faecalis. (P<0.01). EAP was associated with the presence of T. denticola (P<0.01). CONCLUSION: T. denticola was associated with symptomatic endodontic disease in the presence of apical bone resorption. E. faecalis was associated with treatment failures. We suggest that these species may play critical roles in endodontic pathology.     

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     

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。     

Molecular detection of black-pigmented bacteria in infections of endodontic origin

A 16S rDNA-directed polymerase chain reaction method was used to assess the occurrence of four black-pigmented anaerobic rods in root canal infections. Samples were obtained from 54 infected teeth. Ten cases were diagnosed as acute periradicular abscesses. DNA was extracted from the samples and analyzed using a polymerase chain reaction-based identification assay. The method allowed detection of black-pigmented bacteria anaerobes in 59.3% of the examined teeth. Twelve cases yielded more than one black-pigmented species. In general Porphyromonas endodontalis was found in 42.6%, Porphyromonas gingivalis in 27.8%, Prevotella nigrescens in 7.4%, and Prevotella intermedia in 5.6% of the cases. P. endodontalis was found in 70% of the pus samples, P. gingivalis in 40%, and P. intermedia in 10%. P. gingivalis was always found associated with P. endodontalis in abscessed teeth. P. nigrescens was not found in any pus sample. The high prevalence of P. endodontalis and P. gingivalis suggests that they can play an important role in the pathogenesis of periradicular diseases.     

Microorganisms from canals of root-filled teeth with periapical lesions

AIM: The objective of the present study was to identify the microbial flora within root canals of teeth with failed root-canal treatment and to determine the association of the various species with clinical features. METHODOLOGY: Sixty root-filled teeth with persisting periapical lesions were selected for this study. During nonsurgical endodontic re-treatment, the root-filling material was removed and the canals were sampled. Microbial sampling, isolation and species determination were performed using advanced microbiological techniques for anaerobic species. The association of microbiological findings with clinical features was investigated. RESULTS: Microorganisms were recovered from 51 teeth. In most cases, one or two strains per canal were found. Of the microbial species isolated, 57.4% were facultative anaerobic species and 83.3% Gram-positive microorganisms. Enterococcus faecalis was the most frequently recovered bacterial species. Obligate anaerobes accounted for 42.6% of the species and the most frequently isolated genera was Peptostreptococcus. which was associated with clinical symptoms (P < 0.01). Significant associations were also observed between: (a) pain or history of pain and polymicrobial infections or anaerobes (P < 0.05): (b) tenderness to percussion and Prevotella intermedia/P. nigrescens (P < 0.05); (c) sinus and Streptococcus spp. (P < 0.001) or Actinomyces spp. (P < 0.01); (d) coronally unsealed teeth and Streptococcus spp. or Candida spp. (both with P < 0.01). CONCLUSION: The microbial flora in canals after failure of root-canal treatment were limited to a small number of predominantly Gram-positive microbial species. Facultative anaerobes, especially E. faecalis, were the most commonly isolated microorganisms, however, polymicrobial infections and obligate anaerobes were frequently found in canals of symptomatic root-filled teeth.     

Periodontal diseases,caries, and microbial composition of the subgingival plaque in children: a longitudinal study

The present study compares periodontal parameters, caries, and levels of colony forming units (CFU) of bacteria from subgingival plaque of permanent teeth, to those of primary teeth examined 4 years previously. Six children who had periodontitis and 5 who had no periodontitis in primary teeth (groups A and B respectively) were examined. The microbial examination included the number of CFU of the total anaerobic count, Actinobacillus actinomycetemcomitans, Streptococcus mutans and Porphyromonas gingivalis. The differences in CFU values for the permanent teeth between groups A and B were not significant. Group A had significantly higher gingival inflammation values in the permanent teeth than group B. Permanent teeth had significantly higher CFU values of P. gingivalis than the primary teeth. Based on the present limited sample, the number of CFU from bacteria of the subgingival plaque of primary teeth are not an adequate predictor of periodontal disease or caries in the permanent teeth.     

Incidence and antimicrobial susceptibility of Porphyromonas gingivalis isolated from mixed endodontic infections

AIM: To investigate the prevalence of Porphyromonas gingivalis in root canals of infected teeth with periapical abscesses and to investigate the antimicrobial susceptibility of this species to some frequently prescribed antibiotics. METHODOLOGY: Samples were obtained from 70 root canals of abscessed teeth. Microbial sampling, isolation and bacterial identification were accomplished using appropriate culture methods for anaerobic species. The antimicrobial susceptibility of the 20 strains of P. gingivalis isolated was determined by using the E-test. The antimicrobial agents tested were amoxicillin, amoxicillin + clavulanate, azythromycin, benzylpenicillin, cephaclor, clindamycin, erythromycin, metronidazole and tetracycline. RESULTS: A total of 352 individual strains, belonging to 69 different species, were isolated. Eighty three percent of the strains were strict anaerobes and 47.5% of the isolated bacteria were Gram-negative. Porphyromonas gingivalis was found in 20 root canals and was most frequently found in symptomatic cases. Statistically, the presence of P. gingivalis was related to purulent exudates and pain on palpation (both P < 0.05). All P. gingivalis strains were sensitive to amoxicillin, amoxicillin + clavulanate, cephaclor, clindamycin, benzylpenicyllin, metronidazole and tetracycline. The lowest range of minimum inhibitory concentration (MIC) (0.026-0.125 microg mL(-1)) was observed against amoxicillin + clavulanate and clindamycin. The lowest MIC 90 was observed against clindamycin (0.064 microg mL(-1)). One strain was resistant to erythromycin and eight strains were resistant to azythromycin. CONCLUSION: Porphyromonas gingivalis pathogen is isolated with frequency from root canals of infected teeth with periapical abscesses. Amoxicillin, as well as amoxicillin-clavulanic acid and benzylpenicillin were effective against P. gingivalis.     

Repair characteristics of root fractures in permanent anterior teeth

abstract — A follow-up study was made of repaired root fractures in 51 permanent anterior teeth, with a mean observation period of 6 years. The material was subdivided into three repair types (Figs. 1–3): Type 1—invisible or hardly discernible fracture line (15 teeth), Type 2—fragments separated by a narrow radiolucent line and peripheral rounding of the fracture edges (33 teeth), and Type 3—fragments separated by a distinct bony bridge (3 teeth). The majority of repaired teeth gave a normal or slightly decreased response to electric pulp tests and the mobility was physiologic or slightly increased. Reduced transparency or slight yellowish discoloration was observed in 14 teeth. The most conspicuous radiographic finding was pulp obliteration which occurred in 86%. Two different patterns were observed: (1) partial obliteration located in the apical fragments and the fracture area, and extending 0.5–4 mm into the coronal fragment, and (2) progressive obliteration of the entire pulp cavity ending with almost total obliteration. Pulp necrosis did not develop as a sequel to progressive obliteration in any case. Several different characteristics of the fracture influenced the repair pattern, the most important being the degree of fragment dislocation and mobility, stage of root development and localization of the fracture. Correlation between type of repair and various treatment procedures was observed only with regard to reduction.     

预防矫治后前牙旋转拥挤复发的临床研究

目的　评价改良嵴上纤维切断术(MSF)及邻面去釉接触区成形术(CPR)防止矫治后前牙旋转拥挤复发的有效性及可行性。方法　129例前牙旋转拥挤患者随机分为实验组和对照组。对照组81例仅作固定矫治;实验组 48例患者除作固定矫治外,其中23例行上下前牙MSF和CPR,余25例只作上下前牙MSF;术后3组均戴维持器1·8~ 2·3年。所有患者在安放固定矫治器前(T1期)、去除固定矫治器时(T2期)和去维持器后2·4年(T3期)各取牙模1副, 比较3组患者的不整齐指数(IRID)。结果　实验组拥挤旋转复发率平均低于对照组21·6%(P<0·001);实验组内:双因素组(MSF+CPR)下颌复发率较单因素组(MSF)低6·56%(P<0·05),但两组在防止上颌拥挤复发上无显著性差异 (P>0·05)。结论　MSF能较有效地防止矫治后前牙拥挤旋转复发,MSF配合CPR对维持下前牙矫治后的稳定具有显著效果。     

Effects on permanent teeth after luxation injuries to the primary predecessors: a study in children assisted at an emergency service

Abstract – Aim: The purpose of this study is to evaluate the developmental disturbances in permanent teeth as a result of luxation injuries in the primary teeth predecessors. Materials and methods: A total of 5330 records, corresponding to 10 years attendance at the Emergency Center of Baby Clinic, Londrina State University, Brazil, were analyzed. Three hundred and eighty nine children were involved in this study, totaling 620 traumatized primary teeth. Clinical and radiographic examinations were carried out in the permanent successor teeth. Results: In total, 623 permanent teeth were examined and developmental disturbances were detected in 126 teeth (20.2%). The white or yellow‐brown discoloration of enamel was the clinical disturbance most observed (78.0%) and the crown alteration most detected through radiographic analysis was hypoplasia (86.0%). Root alterations were rare; root dilaceration was observed in only one case. The age of the children when their primary teeth received damage varied between 6 and 36 months (P = 0.000325). Intrusive luxation and avulsion were related with most of the cases of sequelae in the successor permanent teeth (P = 0.000001). Conclusion: The results of the present investigation emphasize the special attention required for children who suffered dental trauma at an early age, especially in cases of intrusive luxation and avulsion.     

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.     

Microbiological findings and clinical treatment procedures in endodontic cases selected for microbiological investigation

The relationship between bacteriological findings and clinical treatment procedures was investigated in root canal treatment cases that were selected for bacteriological investigation by general dental practitioners in Finland. The cultures were sent to the Oral Microbiological Service Laboratory at the Institute of Dentistry in Helsinki. Two groups of teeth were selected based on the type of infection present in the root canal system. The 'enteric bacteria' group consisted of 40 sequential cases where Enterococcus faecalis and/or other facultative enteric bacteria or Pseudomonas sp. were found in the samples in pure culture (35%) or together with other types of bacteria. The group 'non-enteric bacteria' consisted of 40 sequential cases where only non-enteric bacteria were found. The dentists who had sent the bacteriological samples received a questionnaire where they were asked about the treatment protocol and procedures. A total of 70 out of 80 questionnaires were returned. If the root canals had been unsealed at some point during the treatment, enteric bacteria were found more frequently than in canals with an adequate seal between the appointments. Of cases with enteric bacteria 55% had been open during the treatment, while in the group where only non-enteric bacteria were found 30% had been open. Enteric bacteria were also more frequently isolated in cases with a high number of appointments before sampling. In the enteric bacteria group 35% of the samples were taken at the 10th visit or later, while the corresponding percentage in the non-enteric group was 3%. In addition, the number of retreatment cases was significantly higher, 12 out of 34, in the enteric bacteria group than in non-enteric bacteria group, which was five out of 36. Other clinical parameters showed no differences between the two groups. The results emphasize the importance of controlled asepsis throughout the root canal treatment.     

Biofilm on the apical region of roots in primary teeth with vital and necrotic pulps with or without radiographically evident apical pathosis

Aim  To evaluate, by scanning electron microscopy (SEM), the presence of biofilms on the external surfaces of the apical third of roots of human primary teeth with vital or necrotic pulps with and without radiographically evident periradicular pathosis.
Methodology  Eighteen teeth were selected: group I – normal pulp ( n  = 5), group II – pulp necrosis without radiographic evidence of periapical pathosis ( n  = 7) and group III – pulp necrosis with well-defined radiographic periapical pathosis ( n  = 6). After extraction, the teeth were washed with saline and immersed in 0.03 g mL⁻¹ trypsin solution for 20 min. The teeth were then washed in sodium cacodilate buffer and stored in receptacles containing modified Karnovsky solution. The teeth were sectioned, dehydrated in an ethanol series, critical-point dried with CO₂, sputter coated with gold and the external root surface in the apical third examined by SEM.
Results  In the teeth of groups I and II, the apical root surfaces were covered by collagen fibres, with no evidence of bacteria (100%). In the teeth of group III, the root apices had no collagen fibres but revealed resorptive areas containing microorganisms (cocci, bacilli, filaments and spirochetes) in all cases (100%).
Conclusion  Microorganisms organized as biofilms on the external root surface (extraradicular infection) were detected in primary teeth with pulp necrosis and radiographically visible periapical pathosis.     

Root canal treatment in Denmark is most often carried out in carious vital molar teeth and retreatments are rare

AIM: To study the reasons given by a representative sample of Danish general dental practitioners (GDPs) for undertaking root canal treatment and, to investigate their confidence in performing root canal treatment on molar teeth. METHODOLOGY: A questionnaire was sent to 600 Danish GDPs randomly selected from the roster of the Danish Dental Association. They were asked to recall various factors about their experience of the last root filling they completed, including the reason for treatment and the pulp diagnosis. Self-assessments on 100-mm visual analogue scales (VAS) were reported concerning the confidence in performing root canal treatment of a molar. End-point definitions were 'very easy' (0) and 'very difficult' (100), respectively. Time reports of molar treatments were given in categorized groups. RESULTS: The most frequent reason for performing root canal treatment was caries within the tooth involved (55%). The majority of treatments involved teeth with vital pulps (54%). Retreatments were carried out in 2% of the cases. The confidence in performing root canal treatment varied but was relatively high, expressed as VAS-values below 50. The creation of an aseptic working field was regarded as the most difficult procedure followed by root canal preparation. Fifty-six percent of the responders stated a time frame of 46-75 min to complete root filling in a molar tooth. CONCLUSIONS: Root canal treatment in Denmark was reported to be undertaken most often because of caries. Treatment was typically performed in molar teeth with vital pulp. Even though apical periodontitis was frequently noted in root filled teeth, retreatments were rare. From a subjective perspective root canal treatment was not considered to be very difficult and was carried out relatively rapidly.     

Monkey pulp reactions to restorative materials

Abstract — Deep buccal cavities in 99 teeth in eight young monkeys were filled with the following combination of materials: a light-cured microfilled composite with or without a base, a chemically cured composite with a base, a silicate cement, and a zinc oxide-eugenol cement. The acid etch technique and intermediate layer of resin was used in the composite group. Pulp reactions and presence and location of bacteria were studied after 8 days and after 90 days. In the short observation period the inflammatory reactions were more pronounced when unlined composite fillings were evaluated compared with silicate cement fillings and with lined fillings. Bacteria were seen in all unilined cavities and a significant association between presence of bacteria and moderate to severe inflammatory responses was found. The most severe inflammatory reactions were seen when bacteria were found in the dentinal tubules. After 90 days slight inflammatory changes prevailed in all groups. A significant correlation between bacteria and inflammatory reactions could still be observed.     

Transmission of periodontal disease-associated bacteria from teeth to osseointegrated implant regions

PURPOSE: The presence of periodontopathic bacteria is a risk factor for peri-implantitis. The present study examined colonization by periodontopathic bacteria and their transmission from periodontal pockets to osseointegrated implant sulcus. MATERIALS AND METHODS: Plaque samples were collected from 105 sites in the 15 patients who participated in the study. Colonization by these bacteria was examined by polymerase chain reaction (PCR) and culture. The transmission of periodontopathic bacteria from periodontal sites of natural teeth to the implant sulcus was analyzed by pulsed field gel electrophoresis (PFGE). RESULTS: The PCR detection rates of Porphyromonas gingivalis, Prevotella intermedia, Actinobacillus actinomycetemcomitans, Bacteroides forsythus, and Treponema denticola were 80.0%, 53.3%, 46.7%, 60.0% and 40.0%, respectively. Colonizations by P gingivalis and A actinomycetemcomitans were statistically correlated with periodontal pockets and implant sulcus regions (P < .01). The PFGE patterns of the P gingivalis strains isolated from each patient were identical, but differed from those from other patients. The PFGE patterns of P intermedia strains were identical in 2 out of 3 patients. DISCUSSION: These analyses indicated that there appeared to be transmission of P gingivalis and P intermedia from the periodontal pocket to the peri-implant region. CONCLUSION: Elimination of these periodontal pathogens from the patient's oral cavity before administering dental implant treatment may inhibit colonization by these pathogens and reduce the risk of peri-implantitis.     

The effects on pulp tissue of microleakage in resin composite restorations

The purpose of this study was to evaluate histopathologically the effect on pulp tissue of microleakage in resin composite restorations. Seventy-two class V cavities were prepared on buccal surfaces of monkeys and divided into 3 groups, F, O, and S. Every cavity was etched with 37% phosphoric acid. In group F cavities, each cavity was restored with photo-curable composite without any dentin adhesives. In group O, the cavities were left unfilled. In group S, each cavity was treated with a dentin adhesive system and restored with a restorative composite. After 3, 30, or 90 days, animals were sacrificed and the subjected teeth were immediately removed, then fixed and decalcified. Following sectioning and staining with hematoxylin and eosin or Taylor's modified bacteria staining, each sample was examined with a light microscope. In most teeth with group S cavities, bacterial invasion was not found indicating excellent marginal sealing. The pulpal reaction was much less than that in other groups. In group F as well as in group O, bacteria were frequently observed in the cavity; however, bacteria penetrated into dentinal tubules more in group F than in group O at 30 and 90 days. A correlation between the presence of bacteria and pulpal inflammation was strongly indicated. It was suggested that a leaky restoration was more harmful to the pulp than an open prepared cavity without restoration.     

Cultivable microbial flora associated with persistent periapical disease and coronal leakage after root canal treatment: a preliminary study

AIM: To identify the cultivable bacterial flora in root filled teeth with persistent periapical lesions and to locate their distribution within the root canal system using an in vitro sampling protocol. METHODOLOGY: Eight freshly extracted root filled teeth were collected from the Oral and Maxillo-facial Surgery Department, Eastman Dental Hospital. Seven teeth were associated with persistent apical periodontitis and also showed evidence of coronal leakage. Teeth were transferred to an anaerobic chamber immediately after careful extraction and sectioned transversely to give a crown (in all but one case) and two root segments (coronal and apical). Two samples were obtained from each segment, one from dentine and the other from the restoration or gutta-percha (GP) root filling (46 sites in total). The samples were dispersed, serially diluted and cultured on blood agar and fastidious anaerobic agar (with 5% defibrinated horse blood). The primary growth was subcultured to obtain pure isolates, which were identified by routine microbiological techniques and commercial enzyme tests. RESULTS: A total of 252 strains were isolated from all the teeth. Of all the isolates, the most prevalent bacteria were Gram-positive facultative anaerobes 189/252 (75%) with staphylococci (48/252, 19%), streptococci (44/252, 17%), enterococci (20/252, 8%) and Actinomyces species (20/252, 8%) being found in most of the teeth (6/8, 6/8, 5/8, 5/8 and 7/8, respectively). Of the obligate anaerobes (17%), peptostreptococci (7%) were also present in most teeth (7/8). A statistical association between bacterial flora and site (crown/coronal/apical) or surface (dental/GP/restoration) could not be shown. CONCLUSIONS: The predominant group of bacteria in root filled teeth with persistent apical periodontitis and coronal leakage was Gram-positive facultative anaerobes of which staphylococci followed by streptococci and enterococci were the most prevalent.