Sudden onset of sensitivity to temperature in a tooth that's been filled for a few months. Diagnosis?

The nerve has possibly become inflamed and will require a root canal.

If it was filled with that metal stuff, then there will be some sensitivity to temperature.
1) They didn’t remove all the cavity, before they filled it.
2) The filling cracked and needs to be replaced.

Crack in the tooth.

Oooh, crack in the tooth. That’s a new one.

Are your gums receding? Mine are, due to age, and it’s made my teeth more sensitive.

@IchtheosaurusRex I hope not – I’m not very old.

The dentist was not especially helpful. He took an x-ray and decided that there was no decay, but did not rule out a crack. He gave me a tube of Sensodyne and said to call him when I finished it. Which might be the whole problem – Mom has sensitive teeth, and my dental history is almost identical to her own.

I had a crack in a filling. It hurt to breathe!

@Nullo , Sensodyne made my sensitivity to cold worse. Go figure.