Dental help! Do I need a filling?

[Praed]

Hello! Any advice appreciated from dentists or generally knowledgeable toothy people.

I’ve been told by the dentist that I need a filling, because there’s decay inside my tooth. There is no hole on the outside of the tooth, and no decay on the outside. She said she would need to drill a hole in my tooth and then fill the tooth.

Does this sound right? I’m confused about how a tooth can rot from the inside (but perfectly prepared to believe it’s true); when I asked her she said it had started between the offending tooth and the one next to it, but when I asked if there was decay between the teeth she said no, it’s all inside.

(Background to this is that 20 years ago I visited a different dentist who told me I needed a filling; I didn’t trust him so went to another dentist who said I didn’t need one, and 20 years later that tooth is still fine – it’s not the same one that I’ve been told I need a filling in now. Oh and additionally I had a dentist friend years ago who was financially incentivised to ‘upsell’ unnecessary treatments to patients, which doesn’t help with my trust issues 😣).

Yes sometimes decay is not visible when you look in the mouth, but you can see it on an xray. Also decay between the teeth would be difficult for you to see, but a dentist has a mirror and a pointy probe to feel with and when probing the tooth decayed areas feel slightly softer.
Is this an NHS or private practice?
What type of filling are they putting in, silver amalgam or white composite?

Thank you!

She said there was no decay between the teeth.

It's a private practice and composite filling.