I my upper back teeth have been root canal ed and capped many years ago. i went for a cleaning and now that area hurts. not sensitive to hot or cold and can eat on it. its been a few weeks and still hurts?

Contact your dental office as you may need an exam plus X rays

A deep cleaning could be causing some pain, or canker sore developed in the gums from irritation from cleaning. Have dentist look at other teeth in area that have no root canals or crowns. Pain is not from capped teeth since they have no nerves. Recession of gums from other teeth may be the reason.

Cleaning teeth/gums is a surgical procedure, and as such healing time is required. And especially if you are not flossing daily, the Dentist/Hygienist may have had a challenging task to perform. Call the Dentist's office and report your symptoms. Additional treatment may be required.