A Rat Model Of Periapical Periodontitis For Secondary Root Canal Infections By Enterococcus Faecalis And Its Lesions Progression Evaluation

Objective:To develop a rat model of periapical periodontitis of secondary root canal infections by Enterococcus faecalis(E.faecalis) and investigate the role of X-ray, histochemistry and TNF-a during the inflammation, then comparison its lesions with periapical periodontitis induced by Lipopolysaccharides (LPS).Materials and Methods:(1) Eighteen sprague dawley rats were used in this study. Bilateral first maxillary molar teeth of each rat were exposed pulps, placed absorbent cotton with LPS and exposed in the oral environment to induce periapical lesions, following root canal disinfection for two weeks, the teeth were inoculated with E faecalis suspension and then closed fou four weeks. X-ray and histochemistry in the inflammation were surveyed for one week after inoculation with E.faecalis suspension, before and after root canal disinfection.(2) Thirty rats were used, divided into three group randomly, which were with and without E.faecalis infections with periapical periodontitis, and treatment with periapical periodontitis. then comparison their lesions by X-ray, histochemistry and TNF-a.Results:(1) Periapical lesions were induced in root canal disinfection for two weeks, after inoculation with E.faecalis suspension in root canal, they were significant expanded, and larger than that of before inoculation with E.faecalis suspension. Infiltration of inflammatory cells were cut down at root canal disinfection, cementum hyperplasia was observed at this time. after inoculation with E.faecalis suspension in root canal, acute inflammatory states was detected at one week.(2) The group of E.faecalis infections with periapical periodontitis was most severe on the than others, the periapical lesions expanded, in a time-dependent manner, and peaked on three weeks, chronic inflammatory states were detected at three week, and the expression of TNF-a was climaxed on one week, and then decreased. The group of periapical periodontitis induced by LPS was lesser on the Periapical lesion areas, infiltration of inflammatory cells and the expression of TNF-α. The group of treatment with periapical periodontitis was the least severe one.Conclusions:A rat model of periapical periodontitis of secondary E.faecalis infections can be achieved by treated with root canal disinfection for two weeks, and then inoculated with E.faecalis suspension into the root canal for one weeks. The periapical lesion of it is more severe, continuous bone absorption were observed even in the chronic inflammatory states.