A building body of work indicates that the oral microbiota is intimately connected with human cardiovascular physiology. It was already known that poor oral health, especially gingivitis, is linked with atherosclerosis and heart attacks. A report the journal Free Radical Biology and Medicine suggests that too much oral hygiene might also be bad for cardiovascular health. In this study, Kapil and colleagues provided intriguing evidence that oral nitrate-reducing microbiota influence blood pressure control in humans. When these microbes were eliminated with antiseptic mouthwash, blood pressure measurably increased! This significant result was seen in a relatively small cohort, suggesting a potentially robust effect (one that will need to be confirmed with follow up research).
From the abstract:
“We measured blood pressure (clinic, home, and 24-h ambulatory) in 19 healthy volunteers during an initial 7-day control period followed by a 7-day treatment period with a chlorhexidine-based antiseptic mouthwash. Oral nitrate-reducing capacity and nitrite levels were measured after each study period. Antiseptic mouthwash treatment reduced oral nitrite production by 90% (p < 0.001) and plasma nitrite levels by 25% (p = 0.001) compared to the control period. Systolic and diastolic blood pressure increased by 2–3 .5 mm Hg, increases correlated to a decrease in circulating nitrite concentrations (r2 = 0.56, p = 0.002). The blood pressure effect appeared within 1 day of disruption of the oral microflora and was sustained during the 7-day mouthwash intervention. These results suggest that the recycling of endogenous nitrate by oral bacteria plays an important role in determination of plasma nitrite levels and thereby in the physiological control of blood pressure.”
Even though I knew that obliterating the microbiota in other body locations, like the gut, is harmful, I have been conditioned by dentists and marketers to think that a healthy mouth is one with few bacteria. Not so, apparently! It makes me wonder about other unintended consequences of commonly used antiseptics like chlorhexidine – for instance its use in hand soaps in the hospital. Perhaps we will find that those antibacterial products also can disrupt healthy microbial communities and harm human health.
Read the full text open access article here:
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Joe Alcock
Emergency Physician, Educator, Researcher, interested in the microbiome, evolution, and medicine
EvolutionMedicine 
Perhaps it is only a few select species of Bacteria that are responsible for the Blood pressure lowering effects? There are known pathogenic bacteria in the Oral microbiota.
There are also people who suffer from LOW blood pressure,sometimes quite crippling. May be their dietary Nitrate/Nitrite consumption(eg. excessive cured/preserved meats such as Bacon) together with the Bugs in the mouth are the cause? For these patients Chlorhexidine mouthwash may be a Godsend.