This article may not answer *all* your questions, but I found it very interesting. When my youngest's teeth started coming in, 4 of them were deformed and the pediatric dentist told me I needed to night-wean. DS was only 7 months old. I continued to night nurse, and DS's teeth actually look better now (nearly 3 years later) than they did then.
Anyway, here's the article:
http://www.lalecheleague.org/NB/NBSepOct02p164.html