This is an old thread but since it's been bumped up I thought I'd offer some thoughts and experience.
There's a great book by Ramiel Nagel called "Cure Tooth Decay". He makes many good suggestions including cod liver oil.
Doug Simons' DVD also has good info on caring for cavities well so that they can remineralize.
Years ago I was getting the occasional cavity and I read about how glycerine, a slippery substance which is in almost all toothpastes, actually coats the teeth and prevents them from remineralizing! Wouldn't it be the greatest irony if the very tool that 4 out of 5 dentists recommend to prevent cavities , was preventing the body from healing them on its own???
So, I experimented by quitting toothpaste. It's been 15 years and I've not had a single cavity since! For awhile I used homemade toothpowders but now I just snip a willow twig from my backyard , chew the tip into a "brush" and brush my teeth only with that. It gets my teeth incredibly clean and no more plastic brushes into the landfill for me. You can also buy neem tooth twigs or use other shrubs like hazel, etc.
The other thing I did for my gums was quit dental floss. Do you know that a lot of floss is coated with teflon which can be very irritating to people with sensitivities? After decades of flossing religiously, I stopped cold turkey and my gum "pockets" started closing up and became a non-issue during subsequent dental check-ups.
Having the right minerals in our bodies is essential. Most food is devoid of minerals because of the lack in soils these days. The body knows how to remineralize cavities but we need to have those minerals flowing through our blood, tissues, saliva for the body to do what it knows how to do. We need to grow our own food in soil that is rich in essential and trace minerals. Eating nutrient-dense, high-brix foods will heal our bodies and our teeth and will provide the nutrients for our children to inherit good teeth as well.
Smile everyone!