I doubt you can reverse a cavity in a reasonable amount of time but it may be possible to do it in decades or so. To do this you must know why teeth decay.

We KNOW primitive peoples on primitive diets often have NO to little tooth decay; they also have NO dentists; NO tooth brushes and NO dental floss.

The secret is a very low sugar diet.

The mechanism is this. There is a constant fluid flow through your teeth at all times. When you eat sugar the flow is from the outside of the tooth to the inside of the tooth. With no sugar the flow is from the inside to the outside. This cleanses your tooth from the inside out; just as nature designed us.

Neat eh?

Never visit a toxic dentist again? It is possible.