Influence of the Menstrual Cycle on the Oral Microbial Flora in Women: A Case‐Control Study Including Men as Control Subjects

Background: Changes in the levels of female sex hormones during the menstrual cycle may cause cyclic differences in subgingival bacterial colonization patterns. The purpose of the present study was to test the hypothesis that hormonal changes in the menstrual cycle cause changes in the oral microbiota. Methods: Bacterial plaque samples were collected in 20 systemically and periodontally healthy women using no hormonal contraceptives (test group) over a period of 6 weeks. Twenty age‐matched systemically and periodontally healthy men were assigned to the control group. Samples were processed by checkerboard DNA‐DNA hybridization assay, and 74 species were analyzed. Results: No cyclic pattern of bacterial colonization was identified for any of the 74 species studied in women not using hormonal contraceptives. Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans) (Y4) was common at the beginning of menstruation (mean: 32%) and increased during the following 2 weeks (36%) in women (P