Understanding the Oral-Systemic Connection

Pediatrician examining cute smiling childs throat
            Read time: 4 minutes

A well-established link has been documented between periodontal disease and cardiovascular diseases like atherosclerosis, coronary heart disease, and acute coronary events, including myocardial infarction.1-6 Meta-analyses have associated periodontal disease with elevated bacterial exposure, coronary heart disease, and early atherogenesis;5,7 a study in 2019 showed—for the first time—the common presence of bacterial DNA from viridans streptococci in aspirated thrombi of patients with acute ischemic stroke.8 The authors of this latter study conclude that Streptococcal bacteria, mostly of oral origin, may contribute to the progression and thrombotic events of cerebrovascular diseases.8 Other evidence suggests that oral health and systemic disease are indeed linked—what’s healthy for the mouth is also healthy for the rest of the body, and vice versa.9-13

According to the 2000 US Surgeon General’s report, Oral Health in America, oral examinations can reveal signs and symptoms of more than 90% of systemic diseases.14 However, despite this association, some researchers feel there is a lack of awareness in the healthcare community on their possible importance.14,15 Nutrition-oriented physical exams, as taught in functional medicine, can help clinicians identify early warning signs of systemic disease. In the following video, IFM educator Michael Stone, MD, MS, identifies the signs to look for in the mouth during the patient physical exam:

IFM educator Michael Stone, MD, MS, is a board-certified family physician who practices in Ashland, Oregon. His interests and lectures have covered a wide range of topics—bezoars, neonatal hypocalcemia, exposure to vitamin D and chronic disease—and many subjects in between.

There are approximately 800 species of bacteria that have been identified in the oral cavity, and periodontal disease is the most common oral condition in the population.16 In 2008, a systematic review found that periodontitis is a risk factor for coronary heart disease.17 One meta-analysis found that periodontal disease causes a 19% increase in the risk of cardiovascular disease.17,18 This increase in relative risk rises to 44% among individuals aged 65 years and over.18

In addition to cardiovascular diseases, some studies suggest that infections in the oral cavity are contributing factors in systemic inflammatory diseases such as diabetes.9-11,19 New data suggest that this association is not indicated by traditional clinical signs of periodontal disease but rather by a cluster of host immune and inflammatory mediators.10 A 2015 study examining the relationship between periodontal microbiota and early diabetes risk found that higher levels of four species (A. actinomycetemcomitans, P. gingivalis, T. denticola, and T. forsythia) were associated with a two- to three-fold higher prevalence of prediabetes.20 The study speculates that if bacterial dysbiosis can contribute to prediabetes development in susceptible individuals, it may be possible that periodontitis and prediabetes (or diabetes) are comorbid conditions due to shared microbial risk factors.20

Researchers are calling for further studies into the possible causal associations between oral conditions and systemic disease.21 In 2018, the largest study to date of nearly one million people experiencing more than 65,000 cardiovascular events (including heart attack) found that after accounting for age, there was a moderate correlation between tooth loss (a measure of poor oral health) and coronary heart disease, yet when smoking status was considered, the connection between tooth loss and cardiovascular disease largely disappeared. The researchers concluded that the modest tooth loss–coronary heart disease gradient appeared to be explained by cigarette smoking.22

In a 2014 study, participants with excellent oral hygiene had a significantly lower cardiovascular disease risk compared to those with poor oral hygiene.23 Encouraging healthy oral hygiene (including daily brushing and flossing) and supporting a healthy microbiome are just two ways practitioners can help prevent oral microbial imbalances that may contribute to systemic disease. In fact, the Journal of the American Medical Association recently published a report on the importance of oral health in comprehensive health care, stating that a five-minute oral examination could help physicians not only recognize poor oral health but also detect clues to seemingly unrelated health issues.24

What does this mean for clinicians? Oral health can be easily assessed in the physical exam. Modifiable risk factors that contribute to periodontal diseases include smoking, poor oral hygiene, hormonal changes in females, diabetes mellitus, medications, and stress.16

The functional medicine model recognizes that everything in the body is connected and that conquering heart disease is not simply a matter of driving serum cholesterol down. Understanding the connections between the oral microbiome and systemic diseases may lead to new prevention and treatment opportunities.

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  1. Bochniak M, Sadlak-Nowicka J. Periodontitis and cardiovascular diseases—review of publications. Przegl Lek. 2004;61(5):518-522.
  2. Singer RH, Stoutenberg M, Feaster DJ, et al. The association of periodontal disease and cardiovascular disease risk: results from the Hispanic Community Health Study/Study of Latinos. J Periodontol. 2018;89(7):840-857. doi:10.1002/JPER.17-0549.
  3. Delange N, Lindsay S, Lemus H, Finlayson TL, Kelley ST, Gottlieb RA. Periodontal disease and its connection to systemic biomarkers of cardiovascular disease in young American Indian/Alaskan natives. J Periodontol. 2018;89(2):219-227. doi:10.1002/JPER.17-0319.
  4. Beck JD, Offenbacher S. Systemic effects of periodontitis: epidemiology of periodontal disease and cardiovascular disease. J Periodontol. 2005;76(11 Suppl):2089-2100. doi:10.1902/jop.2005.76.11-S.2089.
  5. Mustapha IZ, Debrey S, Oladubu M, Ugarte R. Markers of systemic bacterial exposure in periodontal disease and cardiovascular disease risk: a systematic review and meta-analysis. J Periodontol. 2007;78(12):2289-2302. doi:10.1902/jop.2007.070140.
  6. Plachokova AS, Andreu-Sánchez S, Noz MP, Fu J, Riksen NP. Oral microbiome in relation to periodontitis severity and systemic inflammation. Int J Mol Sci. 2021;22(11):5876. doi:10.3390/ijms22115876.
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  8. Patrakka O, Pienimäki JP, Tuomisto S, et al. Oral bacterial signatures in cerebral thrombi of patients with acute ischemic stroke treated with thrombectomy. J Am Heart Assoc. 2019;8(11):e012330. doi:10.1161/JAHA.119.012330.
  9. Babu NC, Gomes AJ. Systemic manifestations of oral diseases. J Oral Maxillofac Pathol. 2011;15(2):144-147. doi:10.4103/0973-029X.84477.
  10.  Teng YT, Taylor GW, Scannapieco F, et al. Periodontal health and systemic disorders. J Can Dent Assoc. 2002;68(3):188-192.
  11.  Masthan MK, Anitha N, Jacobina JJ, Babu NA. Oral infections causing systemic diseases. Biomed Pharmacol J. 2016;9(2):863-866. doi:10.13005/bpj/1019.
  12.  Gonzales-Marin C, Spratt DA, Millar MR, Simmonds M, Kempley ST, Allaker RP. Levels of periodontal pathogens in neonatal gastric aspirates and possible maternal sites of origin. Mol Oral Microbiol. 2011;26(5):277-290. doi:10.1111/j.2041-1014.2011.00616.x.
  13.  Byun SH, Lee S, Kang SH, Choi HG, Hong SJ. Cross-sectional analysis of the association between periodontitis and cardiovascular disease using the Korean Genome and Epidemiology study data. Int J Environ Res Public Health. 2020;17(14):5237. doi:10.3390/ijerph17145237.
  14.  US Department of Health and Human Services. Oral Health in America: A Report of the Surgeon General. US Department of Health and Human Services, National Institute of Dental and Craniofacial Research, National Institutes of Health; 2000. Accessed November 8, 2021.
  15.  Bouchard P, Boutouyrie P, D’Aiuto F, et al. European workshop in periodontal health and cardiovascular disease consensus document. Eur Heart J Suppl. 2010;12(Suppl B):B13-B22. doi:10.1093/eurheartj/suq001.
  16.  Nazir MA. Prevalence of periodontal disease, its association with systemic diseases and prevention. Int J Health Sci (Qassim). 2017;11(2):72-80.
  17.  Humphrey LL, Fu R, Buckley DI, Freeman M, Helfand M. Periodontal disease and coronary heart disease incidence: a systematic review and meta-analysis. J Gen Intern Med. 2008;23(12):2079-2086. doi:10.1007/s11606-008-0787-6.
  18.  Janket S-J, Baird AE, Chuang S-K, Jones JA. Meta-analysis of periodontal disease and risk of coronary heart disease and stroke. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2003;95(5):559-569. doi:10.1067/moe.2003.107.
  19.  Hajishengallis G, Chavakis T. Local and systemic mechanisms linking periodontal disease and inflammatory comorbidities. Nat Rev Immunol. 2020;21(7):426-440. doi:10.1038/s41577-020-00488-6.
  20.  Demmer RT, Jacobs DR Jr, Singh R, et al. Periodontal bacteria and prediabetes prevalence in ORIGINS: the Oral Infections, Glucose Intolerance, and Insulin Resistance study. J Dent Res. 2015;94(9 Suppl):S201-S211. doi:10.1177/0022034515590369.
  21.  Joshipura K, Ritchie C, Douglass C. Strength of evidence linking oral conditions and systemic disease. Compend Contin Educ Dent Suppl. 2000;(30):12-23.
  22.  Batty GD, Jung KJ, Mok Y, et al. Oral health and later coronary heart disease: cohort study of one million people. Eur J Prev Cardiol. 2018;25(6):598-605. doi:10.1177/204787318759112.
  23.  VanWormer JJ, Acharya A, Greenlee RT, Nieto FJ. Oral hygiene and cardiometabolic disease risk in the survey of the health of Wisconsin. Community Dent Oral Epidemiol. 2013;41(4):374-384. doi:10.1111/cdoe.12015.
  24.  Lee JS, Somerman MJ. The importance of oral health in comprehensive health care. JAMA. 2018;320(4):339-340. doi:10.1001/jama.2017.19777.


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