When Selena was five years old I noticed a big black hole in her tooth. I took her into the dentist and she had 10 cavities. $2000 dollars later she had had a lot of work done in her poor little mouth.
I stumbled across some people who swore that Vitamin K2 is the go to vitamin for dental health. It is a vitamin that is not found in many foods. The foods with the highest amounts are butter made from the milk of grass fed cows, and fermented soy beans. The claim is that this vitamin is essential to the remineralization of your teeth. That just like bones are constantly regenerating and growing, your teeth are doing the same, assuming they have the necessary supplies. I did not know yhis was possible, but a hygenist friend said it was. There is some limited research that K2 helps with bone regrowth, but overall it isn't a well studied vitamin. Most of the evidence for teeth health is anecdotal.
I decided that I might as well try it. One recommended supplement is a High Vitamin Butter Oil/Fermented Cod Liver Oil mix. It is pretty expensive but after spending $2000 on dentist bills and Selena had yet another black spot on her tooth--I figured it was worth a $50 shot to see if it worked as it could potentially save us a lot of money (what with us not having dental insurance).
I too have had some spots on my teeth that I have been able to get rid of by consistently taking the supplement. One year ago some x-rays showed a cavity between the teeth. In the name of science I have refused to get them fixed because I want to see if they will go away. If they still show up on my next x-rays, then I will have them taken care of.
The other benefit I have noticed from the Cod Liver Oil/Butter Oil supplement is that my skin doesn't burn as easily. I have had quite a few days that I have spent 30 - 40 minutes in the midday sun and have not gotten burnt, which historically has not been possible with my fair, freckled skin. I struggle with knowing what is more risky, no sun exposure, or too much, and I have settled on trying to get as much as possible without getting burnt. Cod liver oil contains vitamin D, which is supposed to help prevent you from getting burnt (the reasoning on why tanning helps to prevent you from getting burnt), and there are some studies that show that vitamin K2 and vitamin D have a synergistic affect that could explain the positive affects in sun protection.
Overall the supplement tastes and smells awful, which is part of the reason I sometimes forget to take it for a while. I buy the "chocolate" flavored kind so I can tell my kids it is a chocolate vitamin, but I still serve it up in a bite of applesauce. That way you can slurp it down without having to taste it.
The positive affects I have seen on both mine and Selena's teeth could be coincidence. There aren't really any scientific studies on its efficacy for cavity healing and/or prevention, and most of the proponents of it are from single group of people*, but I have had enough periods of me or my kids taking it versus not taking it to make me feel like I do see a positive difference that I am willing to spend 50 or so bucks every six months to buy it.
*Weston A Price was a dentist who did some anthropological like research and determined that populations with the healthiest teeth had some sort of "X-Factor" that he seemed to think was found most often in cow's milk during the spring. The Weston A Price Foundation thinks that Vitamin K2 is the name of the X-Factor Price discovered as it is found primarily in milk/butter of cows that eat fresh grass.