Below is an interesting bit of research which gets quite close to tackling your curiosity, or at least stimulating it. It specifically concerns oral hygiene and

Below is an interesting bit of research which gets quite close to tackling your curiosity, or at least stimulating it. It specifically concerns oral hygiene and blood pressure, with a focus on nitric oxide. Tongue scraping seems beneficial, though there's no mention of copper. However, chlorhexidine (mouthwash ingredient) seems a disruptor of NO and may contribute to higher BP. I need to read the article myself, but a brief skim left a big impression. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7589924/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7589924/ Or https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6406172/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6406172/ Edit: I deleted and reposted this comment because I found the article was abridged and might not be the one I remember. I think I've got it right this time, but if not, follow the "full text links". Should be interesting either way.