From the Acta Prize Lecture 2014: the periodontal-systemic connection seen from a microbiological standpoint.

OBJECTIVE: To give an overview of the periodontal-systemic connection seen from a microbiologist.

METHODS: Original research papers, review articles and workshop proceedings were consulted.

RESULTS: Periodontal bacteria can cross epithelial cells, enter the circulation, invade endothelial cells, induce endothelial cell dysfunction and activate inflammatory and immune responses. Several studies support the association between periodontitis (PD) and cardiovascular disease. Severe PD involves a risk for development of type 2 diabetes. Maternal PD is moderately associated with adverse pregnancy outcome and pre-eclampsia. Dental plaque can contain respiratory pathogens able to promote chronic obstructive pulmonary disease and pneumonia. Periodontal bacterial DNA has been detected in synovial fluid of patients with rheumatoid arthritis. Minor evidence exists for associations between PD and chronic kidney disease, obesity, cancer, metabolic syndrome and cognitive impairment. Concerns can be raised as to the interpretation of some study results due to heterogeneity in definitions used for PD, too much weight upon in vitro studies with a few selected organisms and failing recognition that the majority of the periodontal microbiota is not yet cultivated.

CONCLUSION: Periodontal bacteria may participate in extra-oral infections such as CVD, diabetes, APO, pre-eclampsia, COPD, pneumonia, RA, CKD, obesity, cancer, MetS and cognitive impairment. Most knowledge is based on associations which do not necessarily imply causality. Future studies should reach consensus on the definition of PD and systemic disease outcomes, recognize the full spectrum of the microbiota in PD and bacteremia, including not-yet-cultivated organisms and delineate the clinical significance of genetic strain variations and the role of periodontopathogenic vs gut organisms within atheromatous lesions. For demonstration of causality, large, long-term clinical studies should use well-defined criteria for PD and robust disease outcomes to elucidate the importance of PD intervention and prevention.