Göran Sundqvist

Factors affecting the long-term results of endodontic treatment

The influence of various factors that may affect the outcome of root canal therapy was evaluated in 356 patients 8 to 10 yr after the treatment. The results of treatment were directly dependent on the preoperative status of the pulp and periapical tissues. The rate of success for cases with vital or nonvital pulps but having no periapical radiolucency exceeded 96%, whereas only 86% of the cases with pulp necrosis and periapical radiolucency showed apical healing. The possibility of instrumenting the root canal to its full length and the level of root filling significantly affected the outcome of treatment. Of all of the periapical lesions present on previously root-filled teeth, only 62% healed after retreatment. The predictability from clinical and radiographic signs of the treatment-outcome in individual cases with preoperative periapical lesions cases was found to be low. Thus, factors which were not measured or identified may be critical to the outcome of endodontic treatment.

Microbiologic analysis of teeth with failed endodontic treatment and the outcome of conservative re-treatment

OBJECTIVE The purposes of this study were to determine what microbial flora were present in teeth after failed root canal therapy and to establish the outcome of conservative re-treatment. STUDY DESIGN Fifty-four root-filled teeth with persisting periapical lesions were selected for re-treatment. After removal of the root filling, canals were sampled by means of advanced microbiologic techniques. The teeth were then re-treated and followed for up to 5 years. RESULTS The microbial flora was mainly single species of predominantly gram-positive organisms. The isolates most commonly recovered were bacteria of the species Enterococcus faecalis. The overall success rate of re-treatment was 74%. CONCLUSIONS The microbial flora in canals after failed endodontic therapy differed markedly from the flora in untreated teeth. Infection at the time of root filling and size of the periapical lesion were factors that had a negative influence on the prognosis. Three of four endodontic failures were successfully managed by re-treatment.

Intraradicular bacteria and fungi in root-filled, asymptomatic human teeth with therapy-resistant periapical lesions: A long-term light and electron microscopic follow-up study

Light and electron microscopy were used to analyze nine therapy-resistant and asymptomatic human periapical lesions, which were removed as block biopsies during surgical treatment of the affected teeth. The cases that required surgery represented about 10% of all of the cases which received endodontic treatment and root fillings during the period 1977 to 1984. These cases revealed periapical lesions when they were examined 4 to 10 yr after treatment. The biopsies were processed for correlated light and electron microscopy. Six of the nine biopsies revealed the presence of microorganisms in the apical root canal. Four contained one or more species of bacteria and two revealed yeasts. Of the four cases in which bacteria were found, only in one biopsy could they be found by light microscope. In the other three specimens, the bacterial presence could be confirmed only after repeated electron microscopic examination of the apical root canal by serial step-cutting technique. Among the three cases in which no microorganisms could be encountered, one showed histopathological features of a foreign body giant cell granuloma. These findings suggest that in the majority of root-filled human teeth with therapy-resistant periapical lesions, microorganisms may persist and may play a significant role in endodontic treatment failures. In certain instances such lesions may also be sustained by foreign body giant cell type of tissue responses at the periapex of root-filled teeth.

Bacteriologic evaluation of the effect of 0.5 percent sodium hypochlorite in endodontic therapy

The antibacterial effect of 0.5 percent sodium hypochlorite solution as root canal irrigant was studied in fifteen single-rooted teeth. Each tooth was treated at five appointments, and the presence of bacteria in the root canal was studied on each occasion. No antibacterial intracanal dressings were used between the appointments. When 0.5 percent hypochlorite was used no bacteria could be recovered from twelve of fifteen root canals at the fifth appointment. This should be compared with eight of fifteen root canals when saline solution was used as irrigant. These results suggest that 0.5 percent sodium hypochlorite solution is more effective than saline solution as a root canal irrigant.

Ecology of the root canal flora

The root canal represents a special environment in which selective pressures result in the establishment of a restricted group of the oral flora. Population shifts occur over time with obligate anaerobes ultimately dominating the bacterial mix. Bacterial interrelationships and the nutritional supply are key factors in determining the outcome of the infection. Endodontic treatment, apart from directly eliminating bacteria, can completely disrupt the delicate ecology and deprive persisting bacteria of their nutritional source.

Taxonomy, ecology, and pathogenicity of the root canal flora.

The bacteria present in infected root canals include a restricted group of species compared with the total flora of the oral cavity. Conditions exist in the root canal that permit the growth of anaerobic bacteria capable of fermenting amino acids and peptides, whereas bacteria that mainly obtain energy by fermenting carbohydrates are restricted by lack of available nutrients. During the course of infection interrelationships develop between microbial species and population shifts are produced as a result of these interactions. Strong associations between certain species are present. These associations are most likely based on nutritional demands and nutritional relationships. The pathogenicity of the polymicrobial root canal flora is dependent on bacterial synergy.

Isolation of Actinomyces israelii from periapical lesion

Summary A case report is presented of a periapical lesion that was impossible to treat successfully by conventional endodontic therapy. A strain of A israelii was repeatedly isolated, in pure culture, from bacteriologic specimens collected during treatment. There was uncomplicated healing and good bone regeneration after the root of the tooth was filled and periapical surgery was performed. No antibiotics were given. The current case of periapical actinomycotic infection, and those diagnosed earlier by histologic technique, indicate that infections with Actinomyces are a challenge to successful conventional endodontic therapy and that supporting periapical surgery is necessary for the efficient elimination of the infection.

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.

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.

Description of Mogibacterium pumilum gen. nov., sp. nov. and Mogibacterium vescum gen. nov., sp. nov., and reclassification of Eubacterium timidum (Holdeman et al. 1980) as Mogibacterium timidum gen. nov., comb, nov.

A new genus, Mogibacterium, is proposed for anaerobic, non-spore-forming, Gram-positive, rod-shaped bacteria which have been isolated from the periodontal pockets of adult human patients with periodontal disease and infected root canals. The novel isolates, strains D2-18T, BA11a-f and D5-2T, were inert in most of the conventional biochemical tests and phenotypically resemble asaccharolytic Eubacterium species. The protein profiles of whole cells on SDS-PAGE gels and Western immunoblotting reaction analysis distinguished these organisms from type strains belonging to the previously described Eubacterium species. The G + C content of the DNA is 45-46 mol% for Mogibacterium pumilum and 46 mol% for Mogibacterium vescum. The levels of DNA-DNA relatedness of these new species to other Eubacterium species, including Eubacterium limosum, Eubacterium brachy, Eubacterium lentum, Eubacterium nodatum, Eubacterium saphenum, and the more recently proposed Eubacterium minutum and Eubacterium exiguum (reclassified as Slackia exigua), are less than 2%. The DNA-DNA hybridization value between M. pumilum and M. vescum was 30%. Eubacterium timidum exhibited DNA homologies with Mogibacterium species which were low (17 and 18%) but clearly higher than with all the other Eubacterium species. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the closest phylogenetic neighbour of Mogibacterium species was E. timidum, and that these three species represent a novel lineage distinct from the previously described genera of Gram-positive, rod-shaped bacteria. On the basis of phenotypic characteristics and 16S rRNA gene sequence comparisons, it is also proposed that E. timidum is transferred to the genus Mogibacterium gen. nov. as Mogibacterium timidum gen. nov., comb. nov. (type strain ATCC 33093T).