Get a second opinion before letting a doctor or dentist do anything invasive. I have a bunch of fillings from a dentist who pulled the twelve cavities thing on me. I was young and flush with cash, and hadn't been for a while. But it was only after we'd done most of the filling that I recalled my first dentist diagnosing me with fissures and offered to seal them.

I should have gone for a second opinion before letting her drill. Now I have a mouth full of composites but we find 0 cavities every time I go in for a checkup.

She also fucked up one of the fillings and that did get a cavity under it, during Covid. Cost me a tooth.

I had a small hole filled at age 18. The guy drilled too fast/hot, which damaged the tooth, a few years later it specularly died (abscess under the crown etc) and had to be pulled. It probably was only a discoloration because the other teeth held up perfectly, for another decade.