Alendronate inhibits osteocyte apoptosis and inflammation via IL-6, inhibiting bone resorption in periapical lesions of ovariectomized rats.

AIM: To evaluate the effect of alendronate (ALN) on the development of periapical lesions induced in ovariectomized rats. METHODOLOGY: Twenty-five rats were divided into three groups: sham (control), ovariectomy (OVX) and OVX + ALN. One day after OVX, animals from the OVX + ALN group received the medication via gavage. After 9 weeks, the first molars of all animals were submitted to periapical lesion induction. After 21 days, the animals were euthanized. Femurs were analysed for bone mineral density. The blocks of bone tissue containing the mandibular first molars were submitted to histotechnical processing and staining with haematoxylin and eosin (HE) for periapical lesion analysis under conventional microscopy. At the same time, the morphometric analysis of the periapical lesion area was performed in the fluorescence mode, as well as the histoenzimology for the quantification of osteoclasts and 4'-6-diamidino-2-phenylindole staining for the quantification of apoptotic osteocytes. In addition, the first maxillary molars were used for analysis of the gene expression of proinflammatory cytokines (IL-1ß, IL-6 and TNF-α) and osteoclastogenesis markers (RANKL/OPG). The results were submitted to ANOVA and Kruskal-Wallis tests and Tukey and Dunn post-tests (significance level of 5%). RESULTS: Ovariectomy reduced bone mineral density of the femur, and treatment with ALN was able to prevent bone loss (P < 0.001). Regarding the microscopic analysis of the periapical region, the sham and OVX + ALN groups had moderately increased periodontal ligament and inflammatory infiltrate, while the OVX group had these parameters increased intensely. The periapical lesions of the OVX group were significantly larger in area in comparison to the other groups (P < 0.001). The OVX group had the largest amount of apoptotic osteocytes, and ALN was able to prevent the apoptosis of these cells, in addition to significantly reducing IL-6 expression (P < 0.05). OVX and ALN had no effect on RANKL/OPG expression and did not influence the number of osteoclasts around the periapical lesion (P > 0.05). CONCLUSION: The hypoestrogenic condition induced by OVX aggravated bone resorption, inducing the death of osteocytes and provoking larger periapical lesions. ALN treatment inhibited osteocyte apoptosis and inflammation via IL-6, inhibiting bone resorption in periapical lesions of ovariectomized rats.

Effect of intercellular adhesion molecule 1 deficiency on the development of apical periodontitis.

AIM: To evaluate the specific role of ICAM-1 in host responses against endodontic infection. METHODS: Apical periodontitis was experimentally induced in the mandibular first molars of ICAM-1 knockout and wild-type (WT) mice by pulp exposure to the oral environment. At 7, 21 and 42 days following pulp infection, the animals were euthanized and the jaws were prepared for analysis under conventional and fluorescence microscopy (histopathologic and morphometric analysis), immunohistochemistry (polymorphonuclear leucocytes), enzyme histochemistry (osteoclasts and cementoclasts) and RT-PCR (IL-1 α, TNF-α, INF-γ, IL-10, RANK, RANKL and OPG). A generalized linear model with GLIMMIX procedure with Satterthwaite approximation method of degrees of freedom, Tukey-Kramer, pseudo-ranking nonparametric, Bonferroni-Holm multiple testing adjustment, analysis of variance (ANOVA) and the Tukey's multiple comparisons tests were used to evaluate the statistical differences between the groups using SAS 9.4 and the GraphPad Prism 5.0 software (α = 0.05). RESULTS: Compared to WT mice, ICAM-1 knockout mice had significantly greater bone resorption (P < 0.05), reduced recruitment of neutrophils to periapical inflammatory tissues (P < 0.05) and an increased number of fibroblasts (P < 0.05) at all experimental periods. The osteoclast number was significantly higher in ICAM-1 KO than that of WT animals at all times (P < 0.05), while there was no significant difference between the groups regarding cementoclasts. At day 21, the level of IL-1α, RANK, RANKL and IL-10 had increased significantly in tissues from ICAM-1 KO versus WT mice (P < 0.05), while no significant difference was observed in TNF-α and OPG levels (P > 0.05). Tissue levels of INF-γ were significantly lower in ICAM-1 KO than those in WT mice (P < 0.05). CONCLUSION: ICAM-1 deficiency impaired the host response against endodontic infection, resulting in increased tissue destruction.

One-session root canal treatment with antimicrobial photodynamic therapy (aPDT): an in vivo study.

AIM: To evaluate the response of the apical and periapical tissues of dog teeth with apical periodontitis after one-session root canal treatment with and without antimicrobial photodynamic therapy (aPDT) compared with the use of an intracanal dressing. METHODOLOGY: Sixty root canals with an induced periapical lesion were instrumented and assigned to three groups: I, two-session root canal treatment using antibacterial dressing with calcium hydroxide-based paste; II, one-session root canal treatment using aPDT; and III, one-session root canal treatment in which the root canals were filled immediately after biomechanical preparation. The animals were euthanized after a 90-day experimental period. The maxillas and mandibles with teeth were submitted to histotechnical processing and haematoxylin-eosin staining. Descriptive microscopic analysis of the apical and periapical region characteristics was performed, as well as morphometric assessment of the periapical lesion areas in fluorescence microscopy. Quantitative data were analysed statistically by the nonparametric Kruskal-Wallis test and Dunn's post-test (α = 0.05). RESULTS: Group I was characterized by progressive repair, with the presence of fibres, cells and blood vessels. Group II had periodontal ligaments with the presence of collagen fibres and residual inflammatory cells. Group III had a dense inflammatory infiltrate with extensive oedematous areas and fibrillar dissociation, suggesting a persistent inflammatory and resorptive condition. Regarding periapical lesion size, group I had significantly smaller lesions (P < 0.05) than groups II and III, which did not differ significantly from each other. CONCLUSION: 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.

MyD88 knockout mice develop initial enlarged periapical lesions with increased numbers of neutrophils.

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 (α = 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.