My previous dentist would show me the x-rays and explain. He'd point out that a cavity was starting to develop, and what measures I should take to avoid it developing further.
After some years, if it got worse, he'd show me the old x-rays and the new new so I could see the change, and he'd suggest I'd get it fixed now.
My dentist does the same. When I first went there (after not having gone do the dentist for 3-4 years, because I never had any issues with cavities) he told me that there are 4 cavities I need to get fixed. I was very sceptical at first, but agreed to get them done.
He fixed all 4 of them in 20 minutes. When he drilled open one of the teeth, he showed me how it looked with one of these small cameras that you could see live on the screen. It was absolutely obvious that there was a considerable cavity.
Explaining to your customers what needs to be done, proving it with pictures and/or x-rays, and explaining the different options generates a lot of trust.
Same with my dentist that I started going to 2 years ago. I live in a differtnt country now and literally book appointments 3 months in advance with them just so I don't have a bad experience with someone else.
After some years, if it got worse, he'd show me the old x-rays and the new new so I could see the change, and he'd suggest I'd get it fixed now.
Sadly for me he retired recently.