SYSTEMIC DISEASES (N BUDUNELI, SECTION EDITOR) Periodontitis and Respiratory Diseases: What Does the Recent Evidence Point to? Jananni Muthu 1 & Sivaramakrishnan Muthanandam 2 Published online: 3 March 2018 # Springer International Publishing AG, part of Springer Nature 2018 Abstract Purpose of the Paper There is an increase in focus of research to find the relationship between periodontal diseases and systemic illnesses, in particular respiratory diseases. Though numerous literatures have been published to assess the link, the nature of relationship between the two diseases is still unclear. Periodontal diseases and respiratory diseases share a common pathogenesis and risk factors. Periodontal diseases and respiratory diseases including bronchial asthma have an inflammatory nature thus mandate a positive correlation between these. Understanding the relationship can help development of more focused preventive and treatment measures. Recent Findings and Summary The available link suggests that there could be independent association between periodontitis and respiratory diseases. However, more structured studies are needed to establish the causal relationship between the two entities. The link is stronger between nosocomial and ventilator-associated pneumonia and is stronger than for chronic obstructive pulmonary diseases. Keywords Periodontitis . COPD . Pneumonia . Oral care . Review Introduction The relationship between the oral health and overall health is indisputable. This relationship had been documented in an- cient medical practices. It all started with the theory of focal infection that dates to 1900 AD by William Hunter [1]. But this speculation had its basis on personal experiences and anecdotes. Since it lacked strong scientific evidence, it lost its favor around the late 1930s. Later from the 1980s, more well-designed studies were conducted to explore the link between oral diseases, especially chronic periodontal diseases and systemic diseases. Since then, there has been an exponential rise in the number of studies that have investigated links between periodontal disease and various systemic diseases [2]. This led to the emergence of new term in periodontology, the Periodontal medicine proposed in World Workshop in Periodontics in 1996 [3]. Chronic periodontitis, also known as adult periodontitis, is an infectious inflammatory disease caused by the bacteria of the dental plaque, resulting in the progressive destruction of the tissues that support the teeth, i.e., the gingival, the peri- odontal ligament, cementum, and the alveolar bone [4•, 5]. The chronic nature of periodontal inflammation, etiology and pathogenesis, and the infection and inflammatory re- sponse can cause events elsewhere in the body [ 6 ]. Numerous researches in this field have led to understanding the link between periodontitis and systemic diseases [7]. The most studied and linked diseases with periodontitis are cardio- vascular diseases, adverse pregnancy outcomes, diabetes mellitus, and respiratory diseases [8]. Numerous studies have been done to establish the link between respiratory diseases and periodontitis. One of the important reasons for development of respiratory diseases is the oral colonization by respiratory pathogens appears. In ad- dition, reduction in oral bacterial load through periodontal therapies has resulted in reduced incidence of these reparatory illnesses. This suggests a strong link between the two entities. This article is part of the Topical Collection on Systemic Diseases * Jananni Muthu jannpearl@gmail.com 1 Department of Periodontology, Indira Gandhi Institute of Dental Sciences, Pondicherry, India 2 Department of Oral Pathology & Microbiology, Indira Gandhi Institute of Dental Sciences, Pondicherry, India Current Oral Health Reports (2018) 5:63–69 https://doi.org/10.1007/s40496-018-0171-5