Tooth with a root canal & permanent crown sensitive to heat/cold after 4 months?

[mandye30]

This started about a week & a half ago. I can eat things that are warm, but if it’s hot like soup or if it’s a cold drink then I get this dull mild pain that lasts a few seconds. I went to my dentist and got an x-ray done and he told me he doesn’t see any problems with the tooth I had the root canal on or any teeth next to it. With this dull pain, I feel it on that particular tooth, but I still don't know for sure if it's just a tooth that's next to it. He also said something about my gums maybe being sensitive. I'm not sure what to do about it. I've started using Sensodyne for sensitive teeth 5 days ago so I can't give results on that just yet. If any of you have any ideas on what the cause of this sudden sensitivity is and what I can do to stop it, it would be appreciated. Thank you!