Micro-CT analysis of chronic apical periodontitis induced by several specific pathogens

To conduct three-dimensional micro-CT analysis of bone destruction, periapical sclerotic changes and inflammatory root resorption (IRR) to compare the differences between Enterococcus faecalis (Ef)- and Porphyromonas gingivalis (Pg)-induced chronic apical periodontitis (CAP).

Mono-species bacteria-induced CAP was established in the first and second molars of the right maxilla and mandible of male Sprague-Dawley rats. Fifteen animals were divided into three groups with five rats in each group: control group, Ef-CAP group and Pg-CAP group. The maxilla and mandible were harvested and then scanned by micro-CT. Alveolar bone destruction was evaluated by measuring the volume of alveolar bone resorption, bone volume fraction (BV/TV), trabecular thickness (Tb. Th), trabecular number (Tb. N) and trabecular spacing (Tb. Sp). The results were analysed using one-way analysis of variance and Fisher's least significant difference methods (LSD). The sclerotic changes in the periapical bone were graded and the IRR indexes were scored. The data were analysed using the chi-square test.

The alveolar bone resorption volume of the Pg-CAP group was significantly larger than that of the Ef-CAP group (P < 0.01). In the maxilla, both Pg-CAP and Ef-CAP groups had a significant decrease in BV/TV and increase in Tb. Sp (P < 0.01) with the more significant changes of trabecular bone in the Pg-CAP group. A significant reduction of Tb. N was only found in the Pg-CAP group (P < 0.05). There was no significant change in Tb. Th in either group (P > 0.05). In the mandible, except for an increase in Tb. Sp in the Pg-CAP group (P < 0.05), there was no significant change in BV/TV, Tb. Th or Tb. N (P > 0.05). No obvious sclerotic change was observed. IRR was detected in significantly more root surfaces in the Pg-CAP group (240 surfaces, 60%) than those in the Ef-CAP group (178 surfaces, 44.5%) (P < 0.001). The IRR extension was also significantly more advanced in the Pg-CAP group (P < 0.05).

Pg-CAP caused more substantial alveolar bone destruction and IRR than Ef-CAP. The maxilla was more susceptible to CAP in terms of microstructural changes of trabecular bone than the mandible. Tb. Sp was the most sensitive index for evaluating the residual alveolar bone of CAP.