Sensitivy to cold after root canal

I recently had a root canal on tooth number 14, top left molar.  About 5 days later I was drinking a cold beverage that touched the tooth and caused an intense ache that lasted about 2 minutes and gradually subsided.  Of course I knew this could not be, because the tooth should be dead.  I though if I waited another week or so, maybe this would go away, but it didn't.

When I returned to the dentist, I told him I was feeling cold in THIS tooth and he said "No you aren't.  Not possible.  It has to be another tooth."  Though I knew what I was feeling, I also knew that I also knew that teeth 13 and 15 also needed root canals eventually, so I had a root canal done on 15 (both of these were done by an endodontist who also told me that what I was describing was impossible)  I told him that maybe he missed a root, and of course he responded by saying that he doesn't miss roots and seemed rather offended.

Well, it has been two weeks since having the second RC and I'm still having the cold sensitivity in the inner cusp of #14.  It there some x-ray or test that could find out what is wrong?  The particular office uses old time x-rays and technology and I feel they might not be able to get a decent picture of the tooth.

[Jerome Bogin, D.D.S.]

It is possible that #14 has an accessory canal or two canals in one of the roots. if the discomfort persists I would seek out another opinion.