Adult tooth growing back in at the bottom?

Unclear inifo?: I am not sure exactly what you are describing or asking. Are you asking if a tooth can grow back in after it was removed? If that is your question, then, no. It might be a tooth fragment, a bone spicule, or the sharp edge of the remaining bone that is not yet covered with new gum tissue.

I doubt it: If you feel something sharp or hard in a lower adult tooth extraction site, its more likely to be piece of bone or tooth segment. If you see a tooth, it also could be a supernumerary tooth (extra tooth) an x-ray of the site will tell you for certain.