Dont do it. Did you know teeth can actually repair cavities themselves. Something dentist say is not possible. Your saliva delivers nutrients to your teeth and you can even aid it with more beneficial nutrients and minerals. Check the last item on this list. Its a recipe for remineralizing tooth paste. https://brightside.me/inspiration-health/8-simple-ways-to-naturally-reverse-cavities-and-heal-tooth-decay-444110/

You can also use all natural tooth brushes. Make sure the type of root or twig you use is high in minerals like calcium and other beneficial nutrients. https://www.making-healthy-choices.com/natural-toothbrush.html