After removing the old metal filling we found a large crack right down the middle of the tooth. If you look closely you can also see another crack to going to the right half way down the vertical crack. While working on this tooth the lower right corner broke off and we were concerned the tooth may need a root canal or even worse it may need to be extracted. Fortunately we were able to build the tooth up and restore it with a crown, protecting the remaining structure and preventing future pain and tooth loss.