The association between systemic bone density and periodontitis: Confounding or effect modification by oral bacteria?
Brennan, Renee Marie
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Background . Bacterial infection is the primary etiology of periodontal disease, and low systemic bone density has been found to be associated with several clinical manifestations of periodontal disease. The influence of oral bacteria on the association between systemic bone density and periodontal disease is not known. Objectives . To evaluate the associations between systemic bone density and oral bone loss in postmenopausal women and to assess whether oral bacteria modifies those associations. Methods . This cross-sectional study included 1,256 postmenopausal women who were recruited from the Buffalo, NY center of the Women's Health Initiative Observational Study to participate in the Risk Factors for Osteoporosis and Oral Bone Loss in Postmenopausal Women Study. Bone mineral densities (BMD) of the spine, hip, wrist, and total body were measured by dual-energy x-ray absorptiometry. Subgingival plaque samples were taken at the mesiobuccal surface of up to 12 teeth using paper points, and indirect immunofluorescence assays were used for detection of eight bacterial species from these samples. Up to 11 standardized dental radiographs (including four vertical bitewings) were taken and used to measure alveolar crestal height loss (ACH). Results . Subgingival infections with Tannerella forsythensis, Campylobacter rectus, Prevotella intermedia , and Porphyromonas gingivalis were significantly associated with worse ACH loss. T. forsythensis and C. rectus were also associated with lower systemic bone density, but T. forsythensis was more prevalent than C. rectus (37.9% vs. 17.4%) and was, therefore, used for further analyses. We used two different approaches to evaluate the study objectives, including linear regression analyses of the associations with continuous measures of ACH and logistic regression analyses of differences in risk of clinical periodontitis (whole mouth mean ACH 2+mm, one or more sites ACH 4+mm, or tooth loss due to periodontal disease). Infection with T. forsythensis was not determined to be a confounder or effect modifier of the association between systemic BMD and oral bone loss in either the linear or logistic regression analyses. In fact, systemic BMD and infection with T. forsythensis were independently associated with oral bone loss, even after adjustment for age, smoking status, hormone therapy use, weight, education, and calcium and vitamin D supplementation. Importantly, the associations between systemic BMD and oral bone loss differed by age. The linear associations between BMD and ACH were stronger among women < 70 years of age, but the risk of clinical periodontitis with low bone density was stronger for women 70+ years of age. (Abstract shortened by UMI.)