Written by Gurleen Bhogal
The importance of oral health is emphasized upon exploring its relation to other organ systems including the respiratory, circulatory, and urinary system. Due to poor oral hygiene regimens, bacteria and pathogenic substances are able to accumulate in the oral cavity and subsequently, travel to these organ systems through ingestion of food or inhalation. Thus, poor oral hygiene can lead to the worsening of numerous conditions; notable examples include pneumonia, atherosclerosis, and kidney disease. A particular area of concern is the relationship between insufficient oral hygiene and the exacerbation of pneumonia. Clinical interventions, including the implementation of mechanical brushing and the use of the antibacterial agents chlorhexidine or povidone iodine, have been investigated to observe their effects on reducing the incidence rate of pneumonia. The progressive impacts on atherosclerosis and kidney disease have also been explored; well-explained biological backgrounds exist, explaining the connection between periodontitis and the circulatory and urinary systems. Nevertheless, more clinical trials that explore the impact of oral health on various other organ systems are necessary to strengthen our understanding of this correlation and ultimately, enhance overall well-being.
With Canada being in the top 10 of countries with the most prevalent cases of severe gum disease, oral health and hygiene remains a centre of focus for improving the health of Canadians.1 While the general public is most accustomed to learning about the prevention of cavities, reducing plaque, and keeping our gums as pink as possible, emerging evidence underscores that the implications of poor oral health go beyond the oral cavity. Rather, oral health is capable of influencing the well-being of our organ systems.2 Strong oral health can thus be associated with the prevention of various organ system diseases; however, there are limitations in the extent to which oral hygiene can shape the strength or target the weaknesses of our organ systems.
Connecting the Oral Cavity to the Respiratory System
The connection between oral health and the respiratory system has been a keen area of focus with regards to the topic of general health. Providing evidence for this association, a study by Azarpazhooh et al. outlines the mechanism by which oral bacteria impacts the human respiratory system.3 Bacterium, viruses, or other infectious microbials that can cause respiratory illnesses are often held captive in oral cavities, forming reservoirs for these pathogens.3 As harmful pathogens accumulate in these cavities, the infections can then reach lower airways through routes of contamination, such as inhalation and consumption of food as it moves down the gastrointestinal tract.4 The secretion of periodontal disease-associated enzymes —enzymes that are secreted in response to gum infections— can also lead to respiratory infections by creating an adhesive surface for respiratory pathogens to stick to on the teeth.5 This mechanism creates a pro-pathogenic environment, increasing the chances that an individual will acquire a respiratory illness as a result of greater pathogenic material present in the mouth.6It is important to emphasize that despite these biological mechanisms suggesting a strong correlation between poor oral hygiene and respiratory illnesses, these connections have only shown moderate evidence when studied through experimentation.6 These studies show an overall moderate correlation between poor oral hygiene and the development of pneumonia.6
Oral Hygiene Vs. Pneumonia
Numerous clinical studies have reviewed the effectiveness of oral health care programs as a medical intervention in order to reduce the rate of incidence of respiratory diseases; however, the results vary. A systematic review by Manger et al. considered the use of two strong oral antibacterial agents, chlorhexidine or povidone iodine, and observed a strong correlation with reduced incidence rate of pneumonia within the elderly population.6 Chlorhexidine and povidone iodine are able to reduce bacteria accumulation in the oral cavity, and thereby suppress bacteria from travelling to the respiratory tract.7In particular, clinical studies by Silvestri et al. and Sjogren et al. suggest that professional and mechanical care of the oral cavity is effective at reducing the risk of pneumonia.8,9 An additional study by Maarel-Wierink et al. demonstrates that manual toothbrushing, with or without strong ingredients such as povidone iodine, can reduce the rate of incidence of pneumonia within the same population by 67%.10 Although this serves as evidence that the implementation of oral health care programs has the potential to inhibit microbes from reaching the lower airway to cause severe pneumonia, certain studies show that oral hygiene interventions do not affect other factors, such as mortality of those diagnosed with pneumonia.6
Only Respiratory Illnesses?
Despite research studies and clinical trials greatly emphasizing the correlation between oral hygiene and respiratory illnesses, it is suggested that poor oral health can also negatively impact other organs and their corresponding organ systems, including the circulatory and urinary system. Notably, a study completed by Scannapieco et al. has shown that oral diseases, such as the severe gum infection, periodontitis, can influence the development of atherosclerosis.11 This association is hypothesized as periodontitis is often caused by infectious agents that originally reside within the oral cavity.11 These pathogens are then able to enter the bloodstream if ingested or inhaled and subsequently, promote atherosclerosis by contributing to plaque buildup in the arteries; this may ultimately lead to myocardial infarction or stroke.12 With respect to the urinary system, there is strong evidence linking periodontal disease and kidney disease. In the presence of periodontal disease, Rahmati et al. observed a reduction in the glomerular filtration rate: a reliable indicator of how well the kidneys are filtering blood.13 The study suggests that this is due to the elevated levels of IgG —an antibody that fights against the causative pathogens of periodontal disease— which interferes with the filtration process of the kidneys.13
Not so Fast – Limitations
Although numerous studies outline distinct biological mechanisms connecting bacteria within the oral cavity and the respiratory, circulatory, and urinary system, there is limiting clinical evidence suggesting that good oral hygiene alone can significantly decrease the likelihood of developing chronic illnesses or diseases. The clinical trials that test oral hygiene as a medical intervention include small sample sizes, which may not accurately reflect the effectiveness of oral hygiene amongst a range of illnesses and individuals.11 As a result, further research evaluating the implementation of oral hygiene to reduce the progression of diseases is needed.2 The cost-effectiveness and feasibility of implementing oral hygiene intervention plans for individuals with severe respiratory illnesses remains an area of concern as well.3
The relationship between oral hygiene and other diseases such as pneumonia, atherosclerosis and kidney disease are important considerations for future health care interventions and discoveries. Understanding the fundamental physiology behind the oral cavity and its ability to branch out into other organ systems plays an important role in our knowledge about how oral health can influence other organ systems. Despite the existing evidence explaining how oral bacteria can potentially worsen the conditions of respiratory illnesses, further clinical trials are critical in strengthening our understanding of the physiological link between oral hygiene and chronic illness and disease. As a result, clinical studies that explore real-world applications are crucial in finding revolutionary strategies that enhance the health care of individuals that are at risk for developing chronic diseases. Ultimately, underscoring this area of discovery in order to gather more research regarding the link between oral health and other organ systems can be an effective method to enhance our overall well-being.
1. Canadian Dental Association. The state of oral health in Canada. Oral health: A global perspective [Internet]. 2017. Available from:
https://www.cda-adc.ca/stateoforalhealth/global/ [cited 2021 April 27]. 2. Xiaojing Li, Kolltveit KM, Transtad L, Olsen I. Systemic diseases caused by oral infection. Clin Microbiol Rev. 2000;13(4): 547-538. Available from: doi: 10.1128/cmr.13.4.547-558.2000.
3. Azarpazhooh A, Leake JL. Systematic review of the association between respiratory disease and oral health. Journal of Periodontology. 2006;77(9): 1465-1482. Available from: doi: 10.1902/jop.2006.060010.
4. Mantovi RP, Sandri A, Boaretti M, Grilli A, Volpi S, Melotti P et al. Toothbrushes may convey bacteria to the cystic fibrosis lower airways. J Oral Microbiol. 2019;11(1): 1647036. Available from: doi: 10.1080/20002297.2019.1647036.
5. Scannapieco FA, Bush RB, Paju S. Associations between periodontal disease and risk for nosocomial bacterial pneumonia and chronic obstructive pulmonary disease. Ann Periodontal. 2003;8(1): 54-69. Available from: doi: 10.1902/annals.2003.8.1.54.
6. Manger D, Walshaw M, Fitzgerald R, Doughty J, Wanyonyi WL, Gallagher JE et al. Evidence summary: the relationship between oral health and pulmonary disease. British Dental Journal. 2017;222: 527-533. Available from: doi: https://doi.org/10.1038/sj.bdj.2017.315.
7. Hua F, Xie H, Worthington HV, Furness S, Zhang Q, Chunjie L. Oral hygiene care for critically ill patients to prevent ventilator-associated pneumonia. Cochrane Database Syst Rev. 2016;(10): Available from: doi: 10.1002/14651858.CD008367.pub3.
8. Silvestri L, Weir I, Gregori D, Taylor N, Zandstra D, Saene JJV et al. Effectiveness of oral chlorhexidine on nosocomial pneumonia, causative microorganisms and mortality in critically ill patients: a systematic review and meta-analysis. Minerva Anestesiol. 2014;80(7): 805-20. Available from: https://pubmed.ncbi.nlm.nih.gov/24257147/. [cited 2021 April 27]
9. Sjogren P, Nilsson E, Forsell M, Johansson O, Hoogstraate J. A systematic review of the preventative effect of oral hygiene on pneumonia and respiratory tract infection in elderly people in hospitals and nursing homes: effect estimates and methodological quality of randomized controlled trials. Journal of the American Geriatrics Society. 2008;56(11): 2124-2130. Available from: https://doi.org/10.1111/j.1532-5415.2008.01926.x.
10. Maarel-Wierink CD, Vanobbergen J, Bronkhorst E, Schols J, Baat C. Oral health care and aspiration pneumonia in frail older people: a systematic literature review. Gerodontology. 2013;30(1): 3-9. Available from: doi: 10.1111/j.1741-2358.2012.00637.x.
11. Scannapieco FA, Cantos A. Oral inflammation and infection, and chronic medical diseases: implications for the elderly. Periodontology 2000. 2016;72(1): 153-175. Available from: https://doi.org/10.1111/prd.12129.
12. Koren O, Spor A, Felin J, Fak F, Stombaugh, Tremaroli V et al. Human oral, gut, and plaque microbiota in patients with atherosclerosis. Proc Natl Acad Sci U S A. 2011;108(Suppl 1): 4592-4598. Available from: doi: 10.1073/pnas.1011383107.
13. Rahmati MA, Craig RG, Homel P, Kaysen GA, Levin NW. Serum markers of periodontal disease status and inflammation in hemodialysis patients. Am J Kidney Dis. 2020;40(5): 983-9. Available from: doi: 10.1053/ajkd.2002.36330.