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Updated: Aug 23, 2026

Inducing Apical Periodontitis in Mice
Published on: August 6, 2019
Gram-positive rods prevailing in teeth with apical periodontitis undergoing root canal treatment
L E Chávez de Paz1, A Molander, G Dahlén
1Department of Oral Microbiology, Faculty of Odontology, The Sahlgrenska Academy at Göteborg University, Göteborg, Sweden. luis.chavez.de.paz@odontologi.gu.se
Aims:
To identify Gram-positive rods from root canals of teeth with apical periodontitis and to examine their associations with other species.
Methodology:
Consecutive root canal samples (RCSs) from 139 teeth undergoing root canal treatment were analyzed prospectively for cultivable microbes. Gram-positive rods in the first RCS submitted after chemo-mechanical preparation were categorised to genus level by selective media and gas-liquid chromatography (GLC), and identified to species level by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Associations between organisms were measured by odds ratios (OR).
Results:
In the first samples submitted a total of 158 Gram-positive rods, 115 Gram-positive cocci, 26 Gram-negative rods and 9 Gram-negative cocci, were identified. At genus levels Gram-positive rods were classified into: Lactobacillus spp. (38%), Olsenella spp. (18%), Propionibacterium spp. (13%), Actinomyces spp. (12%), Bifidobacterium spp. (13%) and Eubacterium spp. (6%). The most frequent species were Olsenella uli, Lactobacillus paracasei and Propionibacterium propionicum. In subsequent samples taken during treatment, Gram-positive rods were also identified, although the number of strains was considerably reduced. Positive associations were observed between members of the genus lactobacilli and Gram-positive cocci (OR>2).
Conclusions:
Olsenella uli and Lactobacillus spp. predominated over other Gram-positive rods. A possible association exists between Lactobacillus spp. and Gram-positive cocci in root canals of teeth with apical periodontitis receiving treatment.
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