I've had a root canal and a crown placed on #30 molar. However, the reason for the root canal/crown in the first place was a cracked tooth. The tooth in question has always been somewhat tender..it's been approx 6 years. My dentist informed me that the crack must have gone done the root and is now deteriorating under the crown. I will probably have an implant done..the question is if I leave the deteriorating root too long will it actually harm my jaw bone. I am on a 6 month recall with my dentist. Thanks for your input.