how to get rid of Planters wart?

I have a planters wart on the bottom of my heel. I have been to doctors and dermatologists. I have tried the blister way… And freezing… And other chemicals. Right now I am putting apple cider vinegar on it with duct tape. It seems to be working. But will it for good? The wart has turned black and shrunk. For it to turn black, is that because its dying? Should I do any thing else?