A new study  offers a new theory as to how fluoride really works:
The findings revealed that fluoride reduces the ability of the decay-causing bacteria to stick. That would indicate that fluoride contributes to making it easier for teeth to be washed of decay-causing bacteria by saliva, brushing and other activity.
The research was published in Langmuir.
And it raises a question: If this indeed is key to its power, why not opt for a less potentially toxic way of achieving the same results? After all, compounds in a variety of foods – garlic, grapes, apples and cocoa, for instance – have similarly been found to keep bacteria from clinging to tooth enamel. Other foods, such as cranberries  and blackberries , among others , have been found to help keep oral pathogens at bay in other ways.
If non-toxic substances can do the same job, why pick a poison?
This is, of course, the same question we can ask about mercury amalgam fillings versus composite. And the usual answer is that amalgam is cheaper and easier to work with.
But only, as is so often the case, in the short run…