Respiratory infection: how important is oral health?

The oral cavity has long been considered a potential reservoir for respiratory pathogens. Recently, there has been a renewed interest in the relation between oral flora and respiratory infection among "at-risk" patients such as patients from intensive care units or frail older adults. The mechanisms of infection could be colonization of the oral biofilm by respiratory pathogens followed by aspiration. More recent hypotheses relate to the presence in saliva of enzymes and cytokines associated with oral pathogens, and that could modulate the colonization of the respiratory tract or promote infection by respiratory pathogens. It is the aim of this paper to review the recent literature on this topic.