Influence of oestrogen deficiency on the development of apical periodontitis

Aim To evaluate the effects of a long period of oestrogen deficiency on the development of apical periodontitis in rats. Methodology Wistar rats ( n = 24), 3 months old, evaluated by vaginal cytology, were included in the study. Twelve animals were ovariectomized ( OVX group) and the other 12 were sham operated ( control group). One hundred and twenty days after castration, the pulps of the left mandibular first molars were exposed to induce the development of apical periodontitis. Body mass was verified on a weekly basis. Following 21 and 40 days of lesion induction, the animals were sacrificed. Blood was collected for biochemical analysis, and mandibles were removed for radiographic analysis. Comparative analysis of the data was performed by the nonparametric Kruskal-Wallis and Dunn's multiplecomparisons tests. The t-test was applied to compare the oestrogen levels between control and OVX groups. Results Radiographs revealed that apical periodontitis lesions were significantly larger in the 40-day OVX group when compared with both 40-day (P < 0.05) and 21-day (P < 0.001) control groups. Serum oestrogen levels were significantly lower in the OVX group (P < 0.01), confirming the efficacy of castration. Oestrogen deficiency resulted in significantly greater body mass gain (P < 0.01) in 40-day OVX group when compared with 40-day control group. Serum concentrations of calcium were similar between groups (P > 0.05). Alkaline phosphatase levels, although higher in the OVX groups (21 and 40 days), were not significantly different. Conclusions Ovariectomized rats had significantly larger apical periodontitis lesions after 40 days of pulp exposure when compared with controls. These findings suggest that bone alterations as a result of long periods of oestrogen deficiency can influence the progression of apical periodontitis.