Extreme tooth pain under crown

Over Memorial Day weekend I started having pain on the bottom right side of my mouth (dentist said tooth #29 and back) and I have been to the dentist several times to correct the problem.  I have two crowns in those two back molars (did not have root canals on those molars) the dentist said the tooth (#29) appears to be fine (no decay according to X-Ray) and sensitivity may be due to an exposed root (on tooth #29).  He proceeded to apply some type of coating (smelled like nail polish) to cover any exposed areas of tooth #29 and crowns, but I am still having a problem.  That has gotten progressively worse.  I can not eat on that side of my mouth and I have to take 2-3 advil at a time several times a day to get rid of the pain.  Over the last couple of days I realized when I touch the crown next to tooth #29 I get extreme pain.  Could the crown have come loose or could there be an infection under the crown?  If so, how would I/my dentist know?  

[Jerome Bogin, D.D.S.]

I would definitely check out the tooth that is sensitive to touch for possible root canal therapy.

[jlounge]

see a endodontist i have worked for one for 5yrs