A Comparative Study of Caerin 1.1/1.9 and Calcium Hydroxide in the Treatment of Apical Periodontitis in Rats

Objectives: By establishing a rat model of periapical infection, this study compared the anti‑inflammatory effects of caerin 1.1/1.9 hydrogel and calcium hydroxide paste, aiming to provide a novel therapeutic strategy for refractory apical periodontitis. Methods: Forty-five male Sprague–Dawley rats were randomly divided: caerin 1.1/1.9 (F1/F3) peptide containing gel group (F1/F3, n = 15), calcium hydroxide group (CH, n = 15) and untreated control group (UC, n = 15). The F1/F3 group and CH group animals received an intracanal application of 5 mg/mL F1/F3-loaded hydrogel or calcium hydroxide paste, respectively, into the ipsilateral mandibular first molar immediately (day 0) and subsequently at 7 and 14 days post apical-foramen enlargement. At the 7th, 14th and 21st days after the operation, the degree of infection was comprehensively evaluated through periapical X-ray films, HE staining, immunohistochemical staining, enzyme histochemical staining and ELISA tests. Results: At the 7th and 14th day after operation, the expression of IL-17 and the contents of TNF-α and IL-6 in F1/F3 and CH groups were significantly lower than those in UC group. On the 21st day after the operation, the number of osteoclasts in F1/F3 and CH groups decreased and the expression of OPG increased and the difference was statistically significant (P < .05). Compared with the CH group, the number of TNF-α and osteoclasts in F1/F3 group was significantly decreased on the 14th and 21st day after the operation and the expression of OPG was increased and the expression of IL-6 and IL-17 was decreased on the 21st day after the operation in F1/F3 group (P < .05). Conclusions: The F1/F3 gel showed a more positive trend in regulating the key inflammatory factors and bone immune indicators related to periapical periodontitis compared to the calcium hydroxide paste.