I Had Two Permanent Crowns Placed In November 2015. One

I had two permanent crowns placed in November 2015. One of them is still uncomfortable and now the gums are very inflamed. My dentist keeps telling me to go to an endodontist to see if I need a root canal, but my gut is telling me I have cement left behind or some other issue going on. I had a crown placed in 2013 and it ached for 2+ years until it finally fell off. After re-cementing, no pain. I am very sensitive to metals and just about everything else.

sorry, I don't have money for this. I figured it would cost, but was hoping it wouldn't.