[Booktrope]

One alternative to fluorine that has been shown clinically to be equally or more effective is nanohydroxyapatite, which was developed by NASA some time ago to treat astronauts for loss of tooth enamel and bone density. (Some background info here https://www.oralscience.com/en/ingredients/mhap/

The rights were sold to Japan where a leading toothpaste has for decades used nanohydroxyapatite rather than fluoride. The exclusive rights of the Japanese company have expired, so nanohydroxyapatite toothpaste is not also made in Canada and the US. It's more expensive than fluoride toothpaste but if you'd like to avoid these questions, might be worth it.