Isolation of Actinomyces israelii from periapical lesion

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.

Cell surface structures of Actinomyces israelii

Actinomyces israelii is the most common cause of human actinomycosis, a chronic granulomatous infection. Periapical actinomycosis involving A. israelii has been identified as an important cause of failure of conventional endodontic treatment. Structures on the bacterial cell surface have been implicated in the pathogenicity of Actinomyces. In this study the ultrastructure of A. israelii was investigated by electron microscopy. Negatively stained preparations revealed the presence of hairlike fimbriae protruding through a thick surface coat on some species, whilst thin sectioning disclosed a Gram-positive cell wall surrounded by a fuzzy outer coat. These structures may be important for the pathogenicity of A. israelii.

Susceptibility of Actinomyces israelii to antibiotics, sodium hypochlorite and calcium hydroxide

Actinomyces israelii has been repeatedly implicated as a cause of failure of endodontic therapy. This study investigated the antimicrobial effect of antibiotics as well as intracanal medicaments, sodium hypochlorite solution and calcium hydroxide, on this important pathogen. Growth of A. israelii was inhibited by low concentrations of antibiotics, yet high concentrations were not bactericidal for A. israelii over 1 week. When A. israelii was exposed for 2-6 weeks at concentrations equivalent to clinical serum levels, the antibiotics were lethal. The results reveal a species-specific antibiotic tolerance for A. israelii. Both sodium hypochlorite solution and calcium hydroxide were found to be highly effective in killing A. israelii.

Periradicular curettage

Periradicular curettage is a part of the treatment procedure of periradicular surgery. Its main purpose is to remove pathological periradicular tissues for visibility and accessibility to facilitate the treatment of the apical root canal system, or sometimes for the removal of harmful foreign materials present in the periradicular area. Inflammatory periradicular lesions (granuloma and cysts) are the responses of the periradicular tissues to irritants from the root canal and not from the periradicular area unless medicaments and/or filling materials have been forced through the apical foramina or perforations into the periodontium. Histologically, the inflammatory periradicular lesion is similar to healing granulation tissue, which is composed of cells which have natural and specific immunological defence capability and cooperate by means of cytokines to amplify the protective mechanisms of the host. Accordingly, it is not necessary to completely curette out all the inflamed periradicular tissues during surgery, since this granulation-like tissue will be incorporated into the new granulation tissue as part of the healing process. To control the source of irritants in the root canal is far more important than to remove all periradicular tissues affected by the irritants. The successful removal of all irritants from the root canal system results in resolution of pulpally induced periradicular lesions. In the case where the periradicular lesion is caused by endodontic instruments or cytotoxic filling materials placed in the periradicular tissues, removal of these foreign objects is required for resolution of the lesion.

Pathogenicity of bacteria using a simulated root canal system

The purpose of this study was to investigate the reliability of an implantation test using Teflon-simulated root canals for evaluating the pathogenicity of root canal bacteria. Models including suspensions of lyophilized strains (Actinomyces israelii, Streptococcus faecalis, and Porphyromonas asaccharolyticus) were implanted in rat subcutaneous tissue for 1 wk, and histological changes were observed. Severe inflammation occurred around the models. Among them, P. asaccharolyticus induced the severest inflammatory response. Further study using P. asaccharolyticus was conducted to compare the implantation test's ability to evaluate pathogenicity with that of an injection test at 1, 2, or 4 wk. Tissue injected with a bacterial suspension showed no clear response through the experimental periods, whereas tissue around implantation sites showed a severe response at 1 wk. However, the inflammatory response subsided at later stages. Consequently, further improvement is needed to investigate pathogenicity for long periods.

In vitro evaluation of the effectiveness of calcium hydroxide and paramonochlorophenol on anaerobic bacteria from the root canal

The effectiveness of calcium hydroxide and paramonochlorophenol (PMCP) was tested on anaerobic bacteria isolated from infected root canals, at time intervals 5, 15, 30 and 60 min. The experimental method used was similar to that proposed by the German Society of Hygiene and Microbiology (DGHM), with slight modifications. Testing revealed that calcium hydroxide was significantly more effective than PMCP against the total number of anaerobes. Additionally, it was proved to be quickly and highly effective against some microorganisms related to severe clinical symptoms, such as B. melaninogenicus and P. gingivalis, as well as against actinomyces species.

Pathogenicity of Actinomyces israelii and Arachnia propionica: experimental infection in guinea pigs and phagocytosis and intracellular killing by human polymorphonuclear leukocytes in vitro

Strains of Actinomyces israelii and Arachnia propionica, isolated from clinical cases of failed endodontic therapy, were examined for: (i) their ability to survive and establish themselves in the soft connective tissue that grew into subcutaneously implanted tissue cages in guinea pigs; (ii) cell-surface hydrophobicity; and (iii) phagocytosis and killing by human polymorphonuclear leukocytes (PMNs) under aerobic and anaerobic conditions. Bacteria were inoculated into the tissue cages in guinea pigs and the cage contents were retrieved after 1, 7, 14 and 21 d for culturing and light and electron microscopy. Both bacterial species showed substantial decline in the number of bacteria by day 7 after the inoculation. Thereafter, the A. israelii strain recovered and, by day 21, had started to increase in number. Light and electron microscopy revealed the formation of typical actinomycotic colonies. A. propionica, on the other hand, continued to decline in number during the entire period of experimental infection and did not form colonies. Both strains were hydrophobic, readily phagocytosed and were efficiently killed by human PMNs under aerobic and anaerobic conditions in vitro. These results suggest that the pathogenicity of A. israelii is due to its ability to establish characteristic cohesive colonies consisting of branching filamentous organisms that are enmeshed in an extracellular matrix. It seems that the organisms existing in such colonies can collectively evade destruction and elimination by host phagocytic cells, whereas in vitro suspensions of the bacteria are easily phagocytosed and efficiently killed by PMNs. With respect to A. propionica, further investigations are necessary to understand its pathogenicity.

A microbiological and clinical review of the acute dentoalveolar abscess

Early microbiological studies of acute suppurative dental infection implicated streptococci or staphylococci as the causative microorganisms but recent studies suggest that the microbial flora of acute dentoalveolar abscess is usually polymicrobial, predominantly involving CO2-dependent streptococci, strictly anaerobic Gram-positive cocci and strictly anaerobic Gram-negative bacilli. These differences are probably due to poor sampling techniques and inadequate culture methods used in the early investigations. It is now accepted that specimens should be obtained by aspiration to avoid contamination and processed promptly using strict anaerobic culture. Traditionally the bacterial strains isolated have been regarded as members of the normal oral commensal microflora but it is becoming increasingly apparent from experimental infections that they have pathogenic properties. Although the vast majority of isolates have been found to be sensitive to a variety of antimicrobial agents there would not appear to be a uniformly effective drug. At the present time a penicillin, such as amoxycillin, would probably be the first choice antimicrobial agent with the addition of metronidazole if clinical improvement does not occur.

Bactericidal effects of human neutrophils and sera on selected endodontic pathogenic bacteria in an anaerobic environment

Phagocytosis by normal human neutrophils and the bactericidal activity of normal human pooled serum were measured under anaerobic conditions on six endodontic pathogenic bacterial species from the genera Actinomyces, Bacteroides, Fusobacterium, Peptostreptococcus and Streptococcus. The results revealed that Actinomyces viscosus was not killed either by human neutrophils or by 20 per cent serum; Peptostreptococcus anaerobius was not killed by either 20 per cent or 95 per cent serum; and Bacteroides intermedius was susceptible to both 20 per cent and 95 per cent serum, but was not killed by neutrophils after exposure for 20 minutes. The other species showed intermediate susceptibility patterns. Such results suggest that oral pathogens vary with regard to the bactericidal effects of these two host defense mechanisms, and that this variation may at least in part explain the relative quantities of microbes recovered in certain oral infections.

Antibiotics and endodontics

Antibiotics can be used as an adjunct to endodontic treatment in a number of ways--locally, systemically and prophylactically. The local or intra-canal use of antibiotics in the form of medicaments is common. However, the commercially available agents for this purpose may not be the ideal mixtures. Systemic antibiotics should be restricted to patients who have local signs of infection, malaise and elevated body temperature. Prophylactic use of antibiotics has been recommended for patients 'at risk' of infective endocarditis, in some pre-surgical situations and following avulsion and replantation of teeth. The tendency towards indiscriminate antibiotic use should be discouraged. The use of broad spectrum drugs should be restricted so that these medications remain effective in serious situations.

Capacity of anaerobic bacteria enclosed in a simulated root canal to induce inflammation

In an effort to simulate the infected dental root canal, bacteria were enclosed in polyethylene tubes that were subcutaneously implanted into rats. Four different bacterial combinations, selected from nine oral species, were tested. The contents of 144 inoculated and implanted 'root canals' were analysed after 2 and 4 weeks of implantation. Bacteroides, Streptococcus, Actinomyces and Fusobacterium were inoculated in low numbers but dominated the mixed flora at the end of the experiment. The bacteria-filled tubes induced inflammation of the rat tissue at the implant opening ('foramen'). It is confirmed that mixed bacterial populations survive, show succession and develop within an enclosed environment. Such florae cause significant inflammation at the interface with the host tissues.

A prospective randomized trial on efficacy of antibiotic prophylaxis in asymptomatic teeth with pulpal necrosis and associated periapical pathosis

A recent study from a private endodontic practice compared "prophylactic" antibiotic (high-dose, 1-day) regimens of penicillin V and erythromycin (base or stearate) for patients who had asymptomatic teeth with pulpal necrosis and associated periapical radiolucent lesions (PN/PL). A 2.2% flare-up incidence was found, with no statistically significant differences for penicillin (0.0%), base (2.9%), and stearate (3.8%). No hypersensitivity responses occurred, and gastrointestinal side effects were found primarily with the erythromycins (12.4%). To ascertain whether or not similar results would occur with student operators in a dental school clinic population, the current study was undertaken. One-hundred ninety-five patients with quiescent PN/PL were randomly given either penicillin V or erythromycin (base or stearate). A 2.6% flare-up incidence was found, with no statistically significant differences for penicillin (3.1%), base (1.5%), and stearate (3.1%). No hypersensitivity responses occurred, and GI side effects were found primarily with the erythromycins (17.7%). As can be seen, the results were very similar to those of the recent endodontic practice study. Hence, it can be concluded that the results of the previous endodontic practice study were not unique to any one clinician or method. A comparison was also made between the "prophylactic" penicillin group of the current study and the placebo control group of our previous dental school clinic, student operator study (in which the methods, population, and regimen were almost identical to those of the current study). The results showed that the "prophylactic" penicillin group had significant fewer flare-ups and non-flare-up-associated swelling and pain than did the placebo group. In view of these findings and those from studies from the literature in which "prophylactic" antibiotics were not used, it is our opinion that the antibiotic regimens used in the current study should be a component of clinical endodontic therapy for quiescent PN/PL.

Bacteriologic evaluation of ultrasonic root canal instrumentation

The antibacterial effect of ultrasonic instrumentation in the treatment of infected root canals was clinically evaluated. Sodium hypochlorite solution (0.5%) was used as an irrigant, but no antibacterial intracanal dressing was used between the appointments. The ultrasonic technique eliminated the bacteria from the canals more efficiently than hand instrumentation alone. Even though ultrasonication definitely improves the procedure of root canal disinfection, the use of an antibacterial dressing between appointments is necessary to achieve as complete a reduction in bacterial levels as possible.

Immunoelectron microscopic study of Actinomyces colony in odontogenic periapical infection

A periapical Actinomyces colony was studied by immunoelectron microscopy with a specific antiserum against Actinomyces israelii. Positive as well as some negative micro-organisms were seen within the colony. Reacting antigens were localized in the cytoplasm and the cell wall of the bacteria, which suggests that more than one antigen is involved in the reactions with the present antiserum. The ultrastructural results confirmed the applicability of the peroxidase method with Actinomyces antiserum in paraffin sections for diagnostic purposes.

Actinomyces israelii in osteoradionecrosis of the jaws. Histopathologic and immunocytochemical study of five cases

Five surgically treated patients with osteoradionecrosis of the jaws are presented. The clinical history of the disease varied from 3 to 17 years. In three cases the progression of the disease was enhanced by surgical procedures performed in the irradiated area causing exfoliation of the premaxillary area in one case and spontaneous mandibular fracture in two cases. Actinomyces israelii was demonstrated in tissue sections of all five cases by using FITC-labeled specific antiserum and additionally with peroxidase-antiperoxidase method in one case. Candida was found in histologic sections of three cases. Radiation damage in the oral soft tissues and jawbones makes the atmosphere favorable for anaerobic microorganisms. The present results indicate that the role of A. israelii in the pathogenesis of osteoradionecrosis of the jaws has not been fully appreciated.

Morphometric analysis of chronic inflammatory periapical lesions in root-filled teeth

The cell distribution and the tissue composition of chronic inflammatory periapical lesions were analyzed from seventeen biopsies of root-filled maxillary canines and incisors. The specimens, which included the root tip, the soft granulation tissue, and portions of the surrounding alveolar bone, were subjected to a stereologic analysis based on morphometric point-counting procedures. Plasma cells and lymphocytes were found in large numbers (about 40 percent of the tissue volume) in areas close to the apical foramen. The number of fibroblasts and blast cells was comparatively low in this zone. Neutrophils, monocytes/macrophages, and mast cells accounted each for 1 to 2 percent of the infiltrated tissue volume. With increasing distance from the apex, the tissue examined harbored a decreasing number of inflammatory cells but an increased volume of noninfiltrated connective tissue. It was concluded that long-standing periapical lesions of root-filled teeth had many features in common with those of advanced inflammatory lesions of the marginal periodontium.

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.

Actinomyces of infected dental root canals

The aim of the present study was to identity Actinomyces occurring in infected dental root canals. Out of twenty-five isolated Actinomyces strains, four were A. israelii, four were A. naeslundii, four were A. odontolyticus, and six were A. viscosus. Seven strains could be identified only as Actinomyces spp. The relative frequency of various species of Actinomyces isolated from root canals was similar to that of carious dentin. The Actinomyces strains were usually part of polymicrobial infections. These infections could usually be eliminated by one or two conventional endodontic treatments. In two cases, however, A. israelii was repeatedly isolated in pure culture from the root canals. These two infections had to be eliminated by means of periapical surgery.