Hot&cold sensitivity/painless throbbing on recent root canal/crowned tooth #14. xrays taken & rc failure not indicated & no surrounding cavities! why?

Some possibilities: First, if the rct was completed and the canals were filled properly, there cannot be any cold or hot sensitivity with that tooth. One can still have throbbing if the tissues around the root of the tooth (periodontal ligament) are inflamed. 2d x-rays cannot show everything. A 3d (cbct) scan can possibly show another canal or pathology present. Sometimes these issues resolve on their own with time.

Need Consultation: Recent root canal tooth cannot be sensitive to hot or cold = no nerve in tooth. If it is = then there was a missed canal that was not treated. A root canal specialist dentist needs to evaluate it.

May be another tooth: The pain may be due to inflammation that still remains with the tooth that was treated endodontically or it may be another tooth near the tooth that has been treated.

Another tooth: Hot, cold and throbbing are signs of an inflamed pulpit is very rare on a tooth already treated with a root canal. Sometimes if a canal is missed, this can happen. More common is a pulpitis on an adjacent tooth. You could have a crack causing the problem. I recommend an endodontist for a diagnosis and definitive treatment., .