Can you mix activated charcoal with your toothpaste?

Not a good idea: While some properties of activated charcoal may make it seem like an ideal toothpaste alternative, it is way too abrasive. It's use will result in severe tooth erosion (especially at the gum line) and severe gum recession. The end result is that it will cause more problems then it will solve.

No you can't : Activated charcoal haste very abrasive properties that might damage your teeth enamel by removing its protective layer , the enamel, you can't rebuild your lost enamel , whatever you loose from it , it's permanently lost..