Alteration of the oral microbiota may be a responsible factor, along with estrogen deficiency, by the development of larger periapical lesions.

OBJECTIVES To answer the questions: (1) Does reducing estrogen levels influence the microbial composition of the oral cavity? (2) Does the presence of periapical lesion (PL) cause changes in the oral microbiota? (3) Since estrogen deficiency alters the oral microbiota, can this be one of the factors that contribute to the increase of the PL? MATERIALS AND METHODS Thirty-six rats were divided into four groups: sham (control), ovariectomy (OVX), control with PL (Sham + PL), and OVX + PL. After 9 weeks of OVX, the lower first molars were submitted to PL induction. After 21 days, the microbiological collection of the oral cavity was performed, and the animals were euthanized. The contents were evaluated by the checkerboard DNA-DNA hybridization method, to verify the prevalence of 40 bacterial species (divided into 7 microbial complexes). The blocks containing the lower first molars were submitted to histotechnical processing and staining with hematoxylin and eosin (HE), for the measurement of the periapical lesion area. The results were submitted to ANOVA and Kruskal-Wallis tests and Tukey and Dunn post-tests, with a significance level of 5%. RESULTS In conditions of estrogen deficiency, there was alteration of the oral microbiota. The OVX groups had a higher amount of bacteria compared to the SHAM group in most of the microbial complexes (p 0.001) in any of the microbial complexes. The PLs in OVX animals were significantly higher compared to SHAM animals (p < 0.001). CONCLUSIONS Hypoestrogenicity conditions interfere in the oral microbiota by increasing the amount of bacteria in the saliva and influencing the progression of periapical lesions. CLINICAL RELEVANCE This inedited study shows that deficiency of estrogen leads to alteration of the oral microbiota.