Wow, big job ahead! If you want to get into weirdland with no direct link to Native American herbs that I know of, you might enjoy a look at hunters and gatherers and what they did to get their stunningly nice teeth. Here is a start: Straighter teeth
If you run into teas that were given to young women or preggers you might be able to find the fluoride content. Regular "black tea" from the orient is fairly high, about .5 mg F per cup (Dosage and sources
but I don't give a source, I can dig that up for you if you want it).