I think that is not a ritual but a belief (superstitions) Hmong herbal medication...
My aunt did that to me as a kid to prevent me from having cavities. I remembered it because till this day she still thinks because I did that, I never had any cavities, but brushing and daily maintenance helps
P.S. I have a thing about teeth. Maintain it properly. floss before you brush, and rinse with mouth wash (repeat at least twice a day, three if you do it during midday). You only have one set of permanent teeth so take care of it well.