Here's a very informative article on the subject.
http://www.lowchensaustralia.com/health/teeth.htm
My little boy was 10 months old and 4 pounds when I had his extra baby teeth pulled (4 of them). They were the four canines and they were right on top of each other. According to the article I probably should have done it a little sooner, but anesthesia is always a risk to consider.