"Not sure what kind of soap you would ever be using to substitute toothpaste."

Most commercial soaps include petroleum products, I've heard.

Many people brush their teeth with pure Castile soap, like Dr. Bronner's (the only one I can find around here).

From Wikipedia (yes, I know): "Defluoridation is needed when the naturally occurring fluoride level exceeds recommended limits. It can be accomplished by percolating water through granular beds of activated alumina, bone meal, bone char, or tricalcium phosphate; by coagulation with alum; or by precipitation with lime.[5]

"Pitcher or faucet-mounted water filters do not alter fluoride; the more-expensive reverse osmosis filters remove 65–95% of fluoride, and distillation filters remove all fluoride.[7]"

Lack of fluoride is probably more of a nutritional problem, but America certainly isn't going to admit THAT!

Sue