> Here's a question:  in a situation like mine, would a minor cavity
> heal itself, or is any degradation of the enamel permanent?

Small cavities can be reversed through good oral hygiene.  Enamel
can indeed grow back from a small degradation.  A good dentist will
not fill every cavity as soon as it shows up on an x-ray.  I haven't
had a new cavity that needed to be filled in almost 20 years.

Lisa Sporleder
Ester, Alaska