Night Nursing and Tooth Decay

I have co-slept and night nursed both my children until they were over 2 years old. I am 6 months pregnant with our third child. My second child has 'bottle mouth' and will have his four top front teeth extracted under general anaesthetic at 34 months old. (He has never had a bottle and rarely drinks sugary drinks.) I am appalled that I let this happen to his teeth and whilst I have enjoyed and continue to enjoy being an 'attached parent', I regret immensely not getting him into his own crib and off the breast at night in the first year of his life. I had no idea that such acute tooth decay was a possible result of prolonged and frequent night-nursing. Whilst this did not occur to my first child I don't want to take the risk of this happening to my third baby. Whatever benefits my children may have gained from sharing my bed at night I can't possibly believe they outweigh the disadvantages of a general anaesthetic, surgical intervention, hospitalisation and living without incisors for four years or so. What is your view on this and any advice about how I and other mothers could avoid this situation in the future?