With a root canal being not only very expensive, but prone to complications, I want to be absolutely sure that it is necessary, and will fix my problems. Here’s the background. Lower left molar (19) had old mercury filling. 7 months ago something shifted. Dentist said something about it being deep and it may need root canal, but he was going to try a filling. It worked and all was fine. Then 2 months ago, same tooth felt occasional sensitivity to cold and occasional jolt while biting (feeling only lasted a second then felt fine). Exam & X-rays showed nothing. Last 2 weeks, sensitivity seems to happen random (not triggered by cold beverage.) Not painful at all, just uncomfortable (can brush/floss/rinse/chew/drink fine!) Sensation also occasionally felt on molar above AND on upper right also. Note that I have had teeth grinding issue in past and stress level was pretty high at the time this began. Could this be my issue? Could the filling be faulty and need a re-do? I don’t want to jump in to root canal just because of some slight discomfort. But I also don’t want to wait for pain or infection either. Is there any absolute evidence (other than sensation) to confirm root canal is needed? How long do I wait with these symptoms before acting... I have had three visits to Dentist and Endodontist in last 2 months! Thanks for any feedback!