Characterization of new periodontal and endodontic isolates of spirochetes

A qualitative and semiquantitative SEM study of the morphology of the biofilm on root surfaces of human teeth with endodontic-periodontal lesions

Over the last decades, scanning electron microscopy (SEM) proved to be invaluable for ultrastructural investigation, allowing imaging of the overall appearance and/or specific features of oral biofilms, e.g., microbial colonies and individual cells, glycocalyx, the presence of inorganic products. The aim of this study was the observation and evaluation of the morphology of the biofilm of endodontic-periodontal lesions (EPL) with a modified protocol involving a simplified histologic sample preparation and a low-vacuum SEM examination method. Twenty-one teeth with endodontic-periodontal involvement, extracted for periodontal reasons, were carefully washed with saline, underwent fixation in modified Karnovsky solution and were dehydrated in alcohol series. Samples were examined under low-vacuum SEM. Radicular surfaces were evaluated qualitatively and semiquantitatively for several characteristics, including the presence of bacterial types, the biofilm morphology and the content of root resorptions. Radicular surfaces were divided in four conventional zones Surfaces were evaluated for several characteristics: Presence of bacterial types, biofilm morphology, presence of root resorptions. High-quality images, relevant for endodontic-periodontal biofilms were collected. Continuous, established biofilm was found on all examined surfaces, its detection varying from 19% of the samples on the wall of cemental cone to 52.3% on the radicular surface of the periodontal pocket. Observed microorganisms included cocci, rods an filaments. Spirils and motile bacteria were only accidentally found. SEM investigation of surfaces involved in EPL revealed less surfaces covered by mature biofilm (in only 28.5% of the samples in the ‘transition zone’), especially rods and filaments associated with cemental resorptions and calculus. Biofilm elements were better represented in periodontal pockets than in other zones of EPL (detected in up to 81% of the samples). A strong correlation between mature biofilm and the presence of cocci appears on all investigated zones (P<0.01). Microbiota appeared to be morphologically similar in apical and periodontal areas, especially in old EPL.

A new classification of endodontic-periodontal lesions

The interrelationship between periodontal and endodontic disease has always aroused confusion, queries, and controversy. Differentiating between a periodontal and an endodontic problem can be difficult. A symptomatic tooth may have pain of periodontal and/or pulpal origin. The nature of that pain is often the first clue in determining the etiology of such a problem. Radiographic and clinical evaluation can help clarify the nature of the problem. In some cases, the influence of pulpal pathology may cause the periodontal involvement and vice versa. The simultaneous existence of pulpal problems and inflammatory periodontal disease can complicate diagnosis and treatment planning. An endo-perio lesion can have a varied pathogenesis which ranges from simple to relatively complex one. The differential diagnosis of endodontic and periodontal diseases can sometimes be difficult, but it is of vital importance to make a correct diagnosis for providing the appropriate treatment. This paper aims to discuss a modified clinical classification to be considered for accurately diagnosing and treating endo-perio lesion.

Pathogenesis of apical periodontitis and the causes of endodontic failures

Apical periodontitis is a sequel to endodontic infection and manifests itself as the host defense response to microbial challenge emanating from the root canal system. It is viewed as a dynamic encounter between microbial factors and host defenses at the interface between infected radicular pulp and periodontal ligament that results in local inflammation, resorption of hard tissues, destruction of other periapical tissues, and eventual formation of various histopathological categories of apical periodontitis, commonly referred to as periapical lesions. The treatment of apical periodontitis, as a disease of root canal infection, consists of eradicating microbes or substantially reducing the microbial load from the root canal and preventing re-infection by orthograde root filling. The treatment has a remarkably high degree of success. Nevertheless, endodontic treatment can fail. Most failures occur when treatment procedures, mostly of a technical nature, have not reached a satisfactory standard for the control and elimination of infection. Even when the highest standards and the most careful procedures are followed, failures still occur. This is because there are root canal regions that cannot be cleaned and obturated with existing equipments, materials, and techniques, and thus, infection can persist. In very rare cases, there are also factors located within the inflamed periapical tissue that can interfere with post-treatment healing of the lesion. The data on the biological causes of endodontic failures are recent and scattered in various journals. This communication is meant to provide a comprehensive overview of the etio-pathogenesis of apical periodontitis and the causes of failed endodontic treatments that can be visualized in radiographs as asymptomatic post-treatment periapical radiolucencies.

Identification of spirochetes (treponemes) in endodontic infections

The purpose of this study was to determine the prevalence of spirochetes in asymptomatic infected root canals and in endodontic abscesses/cellulitis. Aseptic clinical samples were collected using paper points from 54 infected root canals and from aspirates of 84 abscesses/cellulitis. Oligonucleotide primers were produced for PCR identification of Treponema vincentii, T. pectinovorum, T. medium, T. amylovorum, T. denticola, T. maltophilum, and T. socranskii. PCR detected spirochetes in 51 of 84 (60.7%) samples from abscesses/cellulitis and in 20 of 54 (37.0%) samples from asymptomatic infected root canals. T. socranskii was the most frequently detected (44.9%), followed by T. maltophilum (29.7%), T. denticola (28.9%), T. pectinovorum (13.7%), and T. vincentii (5.1%). The number of treponema species detected ranged from 1 to 5 species per sample. The mean numbers of species detected were 2.3 in abscesses/cellulitis and 2.6 in infected root canals. Significant association among species was found between T. maltophilum and T. socranskii, as well as between T. maltophilum and T. denticola by determining the odds ratio (> 2.0).

PCR-based identification of Treponema maltophilum, T amylovorum, T medium, and T lecithinolyticum in primary root canal infections

OBJECTIVE

Molecular genetic methods have significantly contributed to the knowledge about the microbiota associated with infected root canals. Albeit spirochetes have been commonly observed in primary root canal infections, only recently they have been identified. The purpose of the present study was to investigate the occurrence of four treponemes-Treponema maltophilum, Treponema lecithinolyticum, Treponema amylovorum, and Treponema medium-in cases of primary endodontic infections associated with different forms of periradicular diseases through a 16S rDNA-based nested PCR assay.

DESIGN

Samples were taken from thirty-one infected root canals associated with either asymptomatic or symptomatic apical periodontitis. DNA extracted from the samples was initially amplified using universal 16S rDNA primers, followed by a second round of amplification using the first PCR products to detect a specific fragment of the 16S rDNA of each target Treponema species.

RESULTS

All cases were positive for the universal bacterial primers, indicating that samples contained bacterial DNA. Of the four target species, T. maltophilum was the most prevalent, being detected in 39% of the cases (33% of the asymptomatic cases and 50% of the symptomatic cases). T. lecithinolyticum was the next more prevalent among the species tested, being found in 26% of the samples (33% of asymptomatic cases and 10% of the symptomatic cases). T. amylovorum was found in 7% of the cases (5% of the asymptomatic cases and 10% of the symptomatic cases), while T. medium was in 13% of the cases (14% of the asymptomatic cases and 10% of the symptomatic cases). None of the species tested was significantly associated with clinical symptoms.

CONCLUSIONS

This was possibly the hitherto first study to report the occurrence of T. lecithinolyticum, T. amylovorum, and T. medium in infections of endodontic origin. Overall, findings suggested that these oral treponemes, particularly T. maltophilum and T. lecithinolyticum, can be involved in the pathogenesis of periradicular diseases.

Treponema socranskii in primary endodontic infections as detected by nested PCR

Spirochetes have been frequently observed in root canal infections, but they were rarely identified. The purpose of this study was to investigate the prevalence of Treponema socranskii in primary endodontic infections using a species-specific nested polymerase chain reaction assay. Samples were collected from 60 teeth having carious lesions, necrotic pulps, and different forms of periradicular diseases. DNA extracted from the samples was initially amplified using universal 16S rDNA primers. A second round of amplification used the first polymerase chain reaction products to detect a specific fragment of T. socranskii 16S rDNA. T. socranskii was detected in 11 of 28 asymptomatic cases (39.3%), five of 12 root canals associated with acute apical periodontitis (41.7%), and five of 20 cases diagnosed as acute periradicular abscesses (25%). There was no relationship between the presence of T. socranskii and the occurrence of symptoms. In general, this spirochete was detected in 21 of 60 samples of endodontic infections (35%). Findings suggest that T. socranskii can be involved in the pathogenesis of different forms of periradicular lesions.

Oral treponemes in primary root canal infections as detected by nested PCR

AIM

To investigate the prevalences of four Treponema species in primary root canal infections using a nested PCR assay.

METHODOLOGY

Samples were obtained from 32 infected root canals. Twenty-two cases showed chronic asymptomatic periradicular lesions and 10 symptomatic cases were diagnosed as acute apical periodontitis. DNA extracted from the samples was initially amplified using universal 16S rDNA primers. A second round of amplification used the first PCR products to detect a specific fragment of the 16S rDNA of each Treponema denticola, T. socranskii, T. vincentii and T. pectinovorum.

RESULTS

Bacteria were present in all cases sampled. T. denticola was detected in 77.3% of the asymptomatic cases, T. socranskii in 40.9%, T. vincentii in 18.2% and T. pectinovorum in 13.6%. In the cases diagnosed as acute apical periodontitis, T. denticola was detected in 80%, whilst T. socranskii and T. vincentii were detected in 40% and 10% of cases, respectively. No symptomatic case yielded T. pectinovorum. In general, nested PCR detected T. denticola in 78.1% of the cases, T. socranskii in 40.6%, T. vincentii in 15.6% and T. pectinovorum in 9.4%. At least one of the four Treponema species was found in 84.4% of the cases examined.

CONCLUSIONS

The species T. denticola was detected in a large number of the cases examined: the prevalence of T. socranskii was also relatively high. The species T. vincentii and T. pectinovorum were also found, but in a smaller number of cases. Based on these data, the recognized pathogenicity of these microorganisms and their involvement with other oral diseases, they should be included in the restricted set of putative endodontic pathogens.

Microbiota of periapical lesions refractory to endodontic therapy

The periapical microbiota of 36 teeth with refractory apical periodontitis was investigated. None of the teeth had responded to conventional endodontic or long-term (> 6 months), calcium-hydroxide treatment. Eight patients had received antibiotics systemically. After anaerobic culture, a total of 148 microbial strains were detected among 67 microbial species. One of the 36 lesions was culture-negative. Approximately half (51.0%) of the bacterial strains were anaerobic. Gram-positive species constituted 79.5% of the flora. Facultative organisms, such as Staphylococcus, Enterococcus, Enterobacter, Pseudomonas, Stenotrophomonas, Sphingomonas, Bacillus, or Candida species were recovered from 27 of the lesions (75%). Sulfur granules were found in 9 lesions (25%). In these granules Actinomyces israelii, A. viscosus, A. naeslundii, and A. meyeri were identified. Other bacterial species, both gram-positive and gram-negative, were detected in the granules as well. Two sulfur granules did not contain Actinomyces. Scanning electron microscopy demonstrated rod- and spirochete-like cells in the granules, and transmission electron microscopy revealed organisms with copious amounts of extracellular material. Outer membrane vesicles were also seen. Some of the granules were calcified. This study demonstrated a wide variety of microorganisms, particularly gram-positive ones, in the periapical lesions of teeth with refractory apical periodontitis.

Identification of oral spirochetes at the species level and their association with other bacteria in endodontic infections

OBJECTIVES

Recent molecular approaches have revealed that fastidious organisms such as Bacteroides forsythus and oral treponemes were frequently found in root canals with apical periodontitis. The purpose of this study was to identify the isolates of oral spirochetes at the species level in endodontic infections and to determine their association with B forsythus and Porphyromonas gingivalis.

STUDY DESIGN

Seventy-nine teeth with apical periodontitis were selected for this study. After sampling from the root canals aseptically, polymerase chain reaction amplification for the 16S rRNA gene was performed with eubacterial universal primers. Subsequently, dot-blot hybridization was performed with 8 species-specific oligonucleotide probes. The microbial associations were analyzed by using the odds ratio.

RESULTS

The most frequently found species was P gingivalis (27.4%), followed by Treponema maltophilum (26%), B forsythus (16.4%), and Treponema socranskii (2.7%). Other treponemes, including Treponema denticola, were not detected in our samples. Significant microbial associations were identified between T maltophilum, B forsythus, and P gingivalis by performing analysis with the odds ratio.

CONCLUSION

Our results indicate that T maltophilum should be included in etiologic studies of endodontic diseases.

Polymerase chain reaction detection of Treponema denticola in endodontic infections within root canals

AIM

A 16S rDNA-based polymerase chain reaction (PCR) method was used to detect the occurrence of Treponema denticola in root canals.

METHODOLOGY

Samples were collected from 54 single-rooted teeth having carious lesions and necrotic pulps. DNA extracted from the samples was amplified using the PCR assay, which yielded a specific fragment of T. denticola 16S rDNA.

RESULTS

T. denticola was detected in 10 of 29 asymptomatic cases (34.5%), eight of 15 root canals that were tender to percussion (53.3%), and five of 10 teeth with acute periradicular abscess (50%). In general, T. denticola was found in 23 of 54 cases (42.6%).

CONCLUSIONS

Findings suggest that T. denticola can be involved in the pathogenesis of periradicular lesions of endodontic origin.

Detection of Treponema denticola in endodontic infections by 16S rRNA gene-directed polymerase chain reaction

A 16S rDNA-based polymerase chain reaction (PCR) method was used to detect the occurrence of Treponema denticola in root canal infections. Samples were collected from 21 single-root teeth having carious lesions, necrotic pulps and radiographic evidences of periradicular bone loss. DNA extracted from the samples was amplified using the PCR assay, which yielded specific fragment of T. denticola 16S rDNA. T. denticola was detected in 11 of 21 cases (52.4%), regardless of the presence or absence of symptoms. Since this spirochete was found in a relatively high percentage of the endodontic infections examined and because it is a pathogenic microorganism involved in periodontal diseases, there are reasons to believe that T. denticola can also participate in the pathogenesis of periradicular lesions of endodontic origin.

Periodontic-endodontic lesions

Lesions of the periodontal ligament and adjacent alveolar bone may originate from infections of the periodontium or tissues of the dental pulp. This review focuses on the relationship of lesions of endodontic origin with lesions of periodontal origin and their classification.

Restriction fragment-length polymorphism analysis of 16S ribosomal RNA genes amplified by polymerase chain reaction for rapid identification of cultivable oral treponemes

Although oral treponemes are among the most frequently found bacteria in periodontal pockets, identification of these organisms can be difficult. In this study, restriction fragment-length polymorphism (RFLP) analysis of polymerase chain reaction (PCR)-amplified 16S ribosomal RNA genes (16S rRNA gene PCR-RFLP) was used to generate restriction profiles of reference strains of oral treponemes including Treponema denticola, Treponema socranskii, Treponema vincentii. Treponema pectinovorum and Treponema medium as well as for Treponema phagedenis and Treponema pailidum and five treponeme strains isolated from human peridontal pockets. Before RFLP analysis, the 16S rRNA gene sequences were obtained from the GenBank database, and the analysis of the theoretical banding patterns for HpaII suggested good species discrimination. 16S rRNA gene sequences were amplified from isolated genomic DNA samples by PCR with spirochete-specific primers. The PCR products were then purified and characterized by single digestion with restriction endonuclease HpaII, and this allowed discrimination between the respective reference strains. Five clinical isolates, four T. denticola and one T. socranskii, were assigned on the basic of their restriction profiles by digestion with HpaII. 16S rRNA gene PCR-RFLP using HpaII is a rapid and reliable method for differentiation of cultivable oral treponemes.

3-hydroxy fatty acids in a lipopolysaccharide-like material from Treponema denticola strain FM

Treponemes are associated with major oral diseases such as apical and marginal periodontitis. Lipopolysaccharide (LPS) is regarded as an important virulence factor in these diseases. It is unclear whether LPS is present in oral treponemes. Therefore, the present study was undertaken to examine if a common oral treponeme-Treponema denticola-possesses LPS. A modified Westphal method (phenol water-ethanol-hexane extraction) was used to extract LPS-like material from T. denticola, reference strain FM. It was cultivated in prereduced anaerobically sterilized pectin medium. Gas chromatography and gas chromatography-mass spectrometry of the extract detected three hydroxy fatty acids: C3-OH-i-13:0, C3-OH-i-15:0, and C3-OH-16:0 which constituted 12% of its fatty acid content. These acids, commonly regarded as markers of LPS, suggested the presence of LPS in T. denticola.