There is a common saying that “a chain is only as strong as its weakest link.” The same concept applies to oral health and how it affects the rest of the body, especially if there is dysbiosis within the oral microbiome. Considering basic anatomy of the body will aid in understanding this relationship. The oral cavity, which is the beginning of the digestive tract, communicates with the sinuses, respiratory tract and digestive tract. It makes sense that the oral cavity would have an effect on multiple systems if compromised. It has taken a long time to recognise that dysbiosis of the oral cavity has an effect beyond the usual suspects of gingivitis, caries and periodontal disease.
However, the advent of molecular techniques, such as 16s ribosomal RNA gene profiling, that identify oral bacterial genetic material have provided insight into correlations with systemic illnesses, such as diabetes, Alzheimer's disease, cardiovascular disease and rheumatoid arthritis.25 While some isolated studies indicate improvement in inflammatory markers and HbA1C levels when periodontal treatment is rendered, there is still not a burden of evidence to conclusively state that oral disease treatment can have a significant effect on systemic health. Much of the evidence is anecdotal, however, anything one can do to improve a patient’s health is worth it. These interventions may provide a more cost-effective way to address or perhaps even prevent some of the costlier chronic diseases.26
For example, there are some types of bacteria that convert the nitrates found in food into nitrites.27 The nitrites are swallowed and converted to nitric oxide, which in turn regulates blood pressure.27 Imagine if these bacteria in the oral microbiome were lost through poor oral health practices or substances that are ingested. The result would be an increase in blood pressure, which could exacerbate the condition in a patient who is predisposed to hypertension. Hypertension is a universal concern, as approximately half of the American population has some form of cardiovascular disease involving chronic hypertension.28 This is just one example of how the oral microbiome can influence systemic health and affect systemic homeostasis. However, when reading the following sections, it is helpful to remember that correlation, rather than causation, is typically being discussed.