My daughter who will be 3 in a few months she has been on phenex 1 and 2 since a few days after she was born. Recently i noticed that her teeth also have started decaying, it started out as a small hole in one of her upper front teeth and the others are turning a darker color, and now the hole is a little bigger. I went to her pku dr. oct. 24 and asked her if the formula was causing it, she told me that it wasnt the formula that it was genetic. I didnt believe her. My daughter will only drink her formula out of a sippie cup, a sports bottle, or a cup with a lid on it with a straw. I thought that that might be a cause of this also but i really think its the fomula. Dr's should tell us what side effects there are before putting someone on these formulas, that way we could try to find a way to prevent them before it happens.