my teeth have gone through various stages like that. i am not sure if it is mercury or other stains, but i do know my teeth are stonger and healthier than they have been in decades. fluoridosis can be hidden by whitening toothpastes, etc. fluoride is the cause of brown brittle teeth, among other worse things you cant see. switch oil if you like but keep pulling. you now know you have a serious dental problem and pulling is the best way i know to let the body address it.