Natural ways of curing tooth decay:

Increase fat soluble vitamins A and D. Taking 1 teaspoon of fermented cod liver oil and 1 teaspoon of high vitamin butter oil daily will increase your fat soluble vitamin A and D levels.
Drink 1 to 2 cups of bone broth daily.
Bone broth is full of magnesium, potassium, calcium, sodium, and minerals (trace minerals) that are depleted from our food supply.
Use a remineralizing tooth paste.
Try oil pulling.
Oil pulling involves putting 1 to 2 teaspoons of coconut oil and 2 drops of essential oil into your mouth and swishing for 10 to 20 minutes.
Once you are done swishing you spit out the oil and rinse with warm water.
Finish by brushing your teeth.
Trace mineral drops.
Take 10 trace mineral drops in the morning. Supplements.
Fermented cod liver oil
Magnesium.Gelatin.Eggshells.
Boil 8 to 10 eggshells in water for about 5 minutes.
Let the eggshells air dry and then grind them into a fine powder.
Ingest ½ a teaspoon a day of the eggshells (you can sprinkle this over your food or just mix with a cup of water)