Progression analysis of periapical periodontitis caused by repeated root canal infection with enterococcus faecalis / 第二军医大学学报

ABSTRACT

Objective To develop a rat model of periapical periodontitis caused by repeated root canal infection with Enterococcus faecalis (E. faecalis), and to evaluate the disease progression by observing the periapical lesion area, inflammation, and TNF-a expression in the root apex. Methods Thirty Sprague Dawley rats were used in this study. The pulps of the bilateral first maxillary molar teeth of each rat were exposed, absorbent cotton with lipopolysaccharides (LPS) was implanted, and then the teeth were exposed in the oral environment for four weeks to induce periapical periodontitis of primary root canal infection with mixed bacteria. Then the root canal was subjected to disinfection treatment for two weeks, followed by inoculation with E. faecalis suspension for one week to produce repeated root canal infection model with E. faecalis for a 3-week observation. X-ray, H-E staining and immunohistochemical staining were used to observe the periapical lesion area, inflammation, and TNF-a expression in the root apex at one week, two weeks, three weeks after establishment of repeated root canal infection model; the above parameters were also observed for periapical periodontitis caused by primary root canal infection with mixed bacteria (6 weeks later) and for root canal disinfected by Ca (OH) (for 6 weeks). Results (1) Periapical periodontitis caused by repeated root canal infection with E. faecalis had gradually increased periapical lesion area, with unclear damage border; the infection reached a severe level during the 1-2 weeks and became chronic inflammation at week three; and the expression of TNF-a began to decrease after two weeks. (2) The periapical periodontitis caused by primary root canal infection with mixed bacteria had a smaller periapical lesion area, with clear damage border, slighter infiltration of inflammatory cells, and less TNF-a expression. (3) The periapical periodontitis with root canal disinfected by Ca (OH)2 had the smallest periapical lesion area, with disappeared inflammation, slight TNF-a expression, and hyperplasia of cementum and alveolar bone. Conclusion E. faecalis has a strong periapical damaging effect, with continuous bone absorption observed even under the chronic inflammatory status.