And how exactly would that work given that viruses proliferation inside our cells?!? The only way you can stop the virus proliferating in the upper respiratory tract through oral and nasal hygiene would be to kill the infected cells, and that's what our immune systems will be doing anyhow.
You clearly know nothing about how viruses function and how viral infections work
I knew from A-Level Biology that viruses replicate inside cells, and I know about inflammation and the immune system having studied physiology. Otherwise, I don't know much about viruses. But I would like to discuss it, if that is allowed? If possible without being insulted?
When viruses have replicated inside the cell, they then exit the cell. So once outside, they could be stopped from infecting other cells.
I googled to find out whether toothpaste kills microbes. The answer seems to be no. However, effective brushing with toothpaste and a decent brush does help to remove microbes from the mouth.
Pneumonia, a complication of coronavirus, is listed here as a health problem associated with not brushing teeth, along with coronary artery disease, dementia, diabetes and pregnancy complications:
"If you don’t brush your teeth and have an overgrowth of bacteria in your mouth, it’s possible to inhale them into your lungs where they can create problems such as pneumonia. Researchers reported that improving oral hygiene among hospital patients reduced cases of pneumonia by 40 percent."
https://tinyurl.com/tgudeeaAlso, saliva kills bacteria and viruses, and brushing the teeth increases the salivary flow rate.
Blowing one's nose will clear it of microbe-containing mucus. That means the microbes will hang around in the tissue or handkerchief. Blowing it again with a used hanky will reintroduce the virus to the nose, hence changing hankies regularly is necessary.