I have a crown that I've had for about 10 months. In that time it has fallen off and been cemented back in place 4 times. It could have been much more, but I've gotten so used to cleaning it and popping it back on myself that I often don't go back to the dentist. It was not a root canal, but a cracked tooth that didn't affect the root. I have no pain in the nub of the old tooth. It is the back left molar, and it'sa totally grey nub. Do I really have to even have this crown if it will never stay on. The have used 3 different cements.