I had a large filling replaced on my lower tooth a couple of months ago. Recently, I began experiencing a sharp pain when I bite down on this tooth. The tooth beside it has a thin crack line all the way to the gum. I couldn't see it in the mirror but I can feel it with my tongue. How can you tell if your tooth is cracked? How can a cracked tooth be fixed?
Thanks for any advice you can give me. :)

Upload image