I'm sorry to any who I have offended by my post. I have strong feelings on this subject (as you could see) because of the stress and pain I have seen several of my neices and nephews go through.
Both my DH and I have genetically soft enamel. I have a tooth condition where my teeth erupt before they are completely developed causing susceptability to cavities almost as soon as they erupt. However, I had only 5 fillings in my mouth. (DH has more.) I brush, floss, and waterpik daily. I told you in my earlier post I'm compulsive about teeth!!
I was only able to nurse my DS for 6 weeks because I had to have benign tumors removed from my breasts and by the time the bruising had subsided what little milk I had to begin with was gone.

However, he was weaned to a cup by 7 months. His first tooth was at 5.5 months old. By his 12 month visit, he had the beginnings of tooth decay on his front top teeth. We had been brushing twice daily until that point. His pediatric dentist recommended brushing after every meal and topical flouride once a day. Six months later the damage is completely reversed.
My nephew--the one I mentioned with the 2 silver implants--was exclusively breastfed, (no bottles ever) until he was 15 months old. His front teeth had to be removed because of "baby bottle tooth decay" that was the dentists diagnosis. I'm not a dentist, or a dental researcher, but I know my nephew never had a bottle. He came across one of my son's bottles once and did not know what to do with it, although he did enjoy spilling it out by squeezing the nipple.... I do know that my SIL does not supervise brushing, or even remind her kids to brush their teeth. When I used the term lazy, I was referring to her, so please don't take offense at my choice of words. Of course I am not a dentist and can't say what the exact cause of it was. I'm not downing extended nursing or anything like that, but I am saying my nephew had portions of the top of his front teeth completely rotted through and brown, and I doubt if he has ever even had mommy "check" his brushing job.
I'm not criticizing anyones else's parenting choices, but my experience has lead me to make teeth a priority. I do believe preventative care is worth the effort.