As far as I know, the active ingredient in the butter oil is recognized to come from rapidly growing grass that the cows eat, so it only comes from butter made in the spring or summer. Green Pastures butter oil, Anchor butter, and Kerrygold butter are some I have had recommended to me.
My daughter's teeth got worse (smaller, and blackening) but still no pain. And now I see other teeth beginning to break down. It's alarming, but I am comforted by her lack of pain, and the hardening I see, even in her discolored teeth. I did notice the downhill slides seemed to happen whenever I ran out of butter oil. It does appear to be early childhood caries, but the theory that it's caused by too much sugar and no brushing is not borne out by my experience. How could it be lack of brushing causing the problem when it's the two front teeth that are having the problem? They're the easiest to reach and brush. Instead, I believe the problem has more to do with diet and ability to use minerals. I've digested "Cure Tooth Decay" by Ramiel Nagel and have been learning to use bone broths and fish in our diets. My aim now is to help her teeth stop decaying and form secondary dentin to make them hard and protected. I keep seeing improvements and backslides alternately.
We have quit using any sugar, and use fruits and honey sparingly. Right now we are also no longer using whole grains of any kind because even the whole grains I was soaking seem only to have contributed to the problem.