No abstract

Bezerra da Silva RA, Nelson-Filho P, Lucisano MP, De Rossi A, de Queiroz AM, Bezerra da Silva LA. Aim To characterize the formation and progression of experimentally induced periapical lesions in teeth of MyD88 knockout (MyD88 KO) mice compared with wild-type (WT) mice. Methodology Periapical lesions were induced in the mandibular first molars of 30 WT and 30 MyD88 KO mice. After 7, 21 and 42 days, the animals were euthanized and the mandibles were subjected to histotechnical processing. Histological sections were stained with haematoxylin and eosin (HE), TRAP histoenzymology, Brown and Brenn staining and immunohistochemistry (RANK, RANKL, OPG). Data were subjected to statistical analysis by the nonparametric Mann-Whitney and Kruskal-Wallis tests and the Dunn post-test, using the SPSS software, version 17.0 (a = 0.05). Results Regarding the periapical lesion size, the MyD88 KO group had significantly higher values than the WT group in the periods of 7 (P = 0.001) and 21 days (P = 0.05). A larger number of neutrophils in the MyD88 KO group were observed (P = 0.01 at 7 days, P = 0.004 at 21 days and P < 0.001 at 42 days). Regarding the number of osteoclasts, no statistically significant difference was observed between the groups at any of the experimental periods (P = 0.884 at 7 days, P = 0.506 at 21 days and P = 0.211 at 42 days). Conclusions In the absence of MyD88, the animals had larger periapical lesions, with a severe inflammatory infiltrate and a significantly larger number of neutrophils.

Two-session root canal treatment using a calcium hydroxide-based dressing was associated with significantly smaller periapical lesions at 90 days and characterized by progressive repair.