Gummie vitamins? Isn't that the pest for bad teeth anyways? And the dentist would def not tell you that you have to check your kids for calcium deficiancy - he would be out of work! No doc would ever do that!
What is eating good? Not a lot of candy and junkfood is very positive... Instead of giving them the gummy vitamins (i'm absolutely sure that they consist of a high precentage of sugar and nothing else!) give them spinach (fresh), other green, leafy veggies, calcium enriched orange juice etc. To eat / drink. Try to buy organic. It is alway better to feed them the vitamins in their natural form, rather than chemical form. Check ingredients and nutrition facts of foods / drinks you feed them. I am almost 100% sure, that you will be able to influence your kids teeth and well being positively by changing their diets. As long as they are still so little, you will have it easier to change to a wholesome, healthy preferably organic diet with lots of fruits and veggies.