This review found that while the definitions used to identify periodontitis were fairly heterogeneous, very few studies met a stringent threshold for periodontitis. Published evidence supports modest associations between some, although not all, of the diseases and conditions reviewed: respiratory disease, chronic kidney disease, rheumatoid arthritis, cognitive impairment, obesity, metabolic syndrome and cancer.
J Clin Periodontol 2013; 40 (Suppl. 14): S8-S19 doi: 10.1111/jcpe.12064