Combinations of bacteria isolated from the root canals of teeth with necrotic pulps and periapical bone destruction were tested for their capacity to induce abscess formation and transmissible infections when inoculated subcutaneously into guinea pigs. Transmissible infections could be induced with combinations obtained from teeth with purulent apical inflammation, but not with combinations from symptomless teeth with chronic apical inflammation. All combinations which gave transmissible infections contained strains of Bacteroides melaninogenicus or B. asaccharolyticus (formerly B. melaninogenicus subsp. asaccharolyticus). The results suggest that purulent inflammation in the apical region in certain cases may be induced by specific combinations of bacteria in the root canal and that the presence of B. melaninogenicus or B. asaccharolyticus in such combinations is essential. However, with one exception, the strains needed the support of additional microorganisms to achieve pathogenicity. The results indicate that Peptostreptococcus micros was also essential. Histological sections of the lesions in the guinea pigs showed that all bacterial combinations induced acute inflammation with an accumulation of polymorphonuclear leukocytes and the formation of an abscess. However, the presence of B. melaninogenicus or B. asaccharolyticus in the combinations resulted in a failure of abscess resolution, with a gradually increasing accumulation of polymorphonuclear leukocytes.

There is still a great need for endodontic treatment in the Swedish population, and no improvement in apical health was found during this 20-year follow up.

Longitudinal studies of endodontic treatment are rare. The purpose of this investigation was to study changes in frequency, technical standard and treatment need in a Swedish population with an interval of 5-7 years. The number of endodontically treated teeth in the population increased while the number of periradicular radiolucencies was at about the same level at the second examination. The number of radiolucencies found in endodontically treated teeth was reduced while it was increased in untreated teeth. The number of root fillings ending less than or equal to 2 mm from the apex of the tooth as well as fillings with a proper seal had increased at the second examination, but still only 40.2% ended less than or equal to 2 mm from the apex of the tooth and 59.1% of the root fillings were judged to have a proper seal. It was concluded that a great need for endodontic treatment existed in the population examined. A slight improvement in the quality of the treatment was evident at the second examination. However, the technical standard was still poor and obviously affected the outcome of the treatment. It is the opinion of the authors that endodontic treatment methods should be simplified as much as possible in an effort to improve the technical quality of the treatment. The prognosis of endodontic treatment would then improve as well.

The purpose of this investigation was to study the frequency and technical standard of endodontic treatment in a Swedish population. The material consisted of full‐mouth radio‐graphic surveys from 200 patients treated by general practice dentists, and the radiographs were analyzed by two observers. Thirteen percent of the teeth had been endodontically treated. Periradicular radiolucencies were found in 5.2% of the teeth and 26.4% of the endodontically treated teeth had such periradicular radiolucencies. In nearly half of the root‐filled teeth, the root filling ended more than 2 mm from the apex, and only 56.3% were judged to have a proper seal. It is concluded that the need for endodontic treatment is great and the technical standard of the root fillings is poor. This strongly indicates that there is a need for standardized endodontic treatment methods and for more specialists in endodontics in Sweden.

The purpose of this study was to evaluate: 1) the use of the conventional buccolingual radiographic projection for estimating the technical quality of endodontic treatment and 2) the effect of the surrounding tissues on these evaluations. The material consisted of three radiographs of each of 108 extracted roots: a clinical radiograph, an in vitro radiograph taken in the buccolingual projection, and an in vitro radiograph taken in the mesiodistal projection. The radiographs were analysed by two observers and consensus was reached and used in the analyses. The agreement between the two observers was good, but statistically significant differences were found between recordings of the seal in the clinical radiographs and the in vitro radiographs taken in the buccolingual projection. The length of the root filling in each of the three projections was interpreted to be the same, while both inadequate seal and visible lumen apical to the root filling were recorded less frequently in the clinical radiographs than in either of the two in vitro projections. This difference was most pronounced in molar teeth. It was concluded that the lengths of root fillings could be measured correctly in clinical radiographs. Due to the anatomy of root canals in incisors and canines, there was a risk of misinterpreting an inadequate seal as adequate in these teeth. The large amount of tissue surrounding molar teeth tended to cause an underregistration of both inadequate seal and lumen apical to the root fillings in these regions.