Same thing. I am always good with flossing twice a day, brushing teeth twice a day (in fact, I spend ~10 mins brushing teeth gently and carefully every day). But the dentist in SF I visited 10 years ago "saw" 4 cavities and he showed me the X-rays, which I didn't know better I should have looked at carefully. But I got 4 fillings. Credit to him, those fillings never had any issue for the last 10+ years.

But I went to a new dentist in FL a few months ago, and that guy told me to refill them because according to him, they are starting to crack (not sure how he saw them in grainy X-rays; he tried to show me one, but I couldn't see it) :D Anyway, I agreed to have them refilled since it's been a while and the cost was reasonable. Now one of the fillings he redid in my molar makes me feel uncomfortable when I chew things with it.

I wrote up a more detailed experience about this in another comment in this post. I hope people see it and learn from it to not trust their dentists easily (esp. the ones you are visiting for the first time).