Two years ago I received a 3 unit dental bridge on the bottom rift side if my mouth.. I have never had any problem with it until now.. About three days ago that side of my mouth became sore. Now the pain is becoming much more intense but is still intermittent. It seems to be worse at night. I have flossed around and underneath the appliance so I do not believe it to be a piece of lodged food. Any help would be appreciated

Are the anchor teeth (or one of them) the problem? Can you pinpoint which area hurts? Your best bet is to go back to the dentist and let him poke around and figure out the problem.

My problem was as WG indicated could be your problem- in my case it was decay in one of the teeth the bridge was anchored to.
Been a while so I can't remember for sure what was done to correct it, a root canal maybe.