If you had a filling in it and the tooth was prepped for a crown you will have a hard time saving it without getting a permanent crown. the tooth was already weak from having the filling then it cracked. There probably isn't enough structure for it to be left the way it is, and will only be problems. The tooth is poisoned from the mercury it had originally. The day for trying to "save the tooth" has come and gone. IMOP you have two option. If you want to save the tooth have a porclein crown made for it. Second option is to pull it. Unless it is in the back I would recommend the crown.