I'm lucky enough not have the bacteria that cause cavities - I'm awful with going to the dentist, but every time I do I walk out without any cavities. However, I do walk out with a stern warning about the dangers of plaque - how it's constant inflammation that causes tooth decay, gum disease, and a multitude of systemic problems - having teeth covered in plaque seems to be a problem in and of itself.

Again, this is drawn mostly from hazy memories of articles previously read, but my understanding was that plaque on the teeth of people who don't eat a diet high in sugars and refined carbs doesn't cause inflammation, ie it's fairly neutral on the teeth and gums. I'm not trying to start a pseudo-science upswell here, though, so maybe ignore this for the time being.