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.
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.