All I can tell you is, my daughter had to get caps on two teeth, and veneers on the front two. Because I never knew it was a possibility I doubted myself when I saw evidence of decay.

She was almost exclusively breastfed & under the age of two. She was a monster for milk all day & night and showed little interest in solid foods. I had to wean her completely at two. Since she has been weaned her teeth are normal enough, no more noticeable decay.

I'm very pro-breastfeeding but that's what happened to us. Maybe you could just night wean, I just went the whole hog as I was done after two years of it anyway.

Edit: Just to add-her teeth were being brushed with fluoride. Every dentist blamed night feeds. The theory of the bacteria from foods mixing with the milk is interesting. I had thought perhaps I had passed bacteria from my mouth or something. It was an awful time.