Tooth ache?

i was at the dentist just a month ago, got a few fillings done. one of my tooth started becoming sensitive to cold, or perhaps it was always sensitive, anyhow, recently, it started hurting like a throb on and off, and it hurts when i put pressure on it, like when i chew. what could this possibly mean, would the dentist have picked up the cavity under the already filled tooth if one existed?

Tooth ache?
There could have been alot of decay in that particular tooth. Sometimes a tooth nerve can be irreversibly damaged even if the decay doesn't actually expose the nerve. If there is an old filling in a tooth, an additional cavity often times does not show up on an x-ray. The additive trauma of replacing the old filling may have also caused the nerve to be irreversibly damaged.This happens often. You may need a root canal.

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