A.C.
We began brushing my son's teeth at about this age. We use Waleda Baby Toothpaste (make sure if you use toothpaste, that it's fluoride-free), and Toms of Maine makes a nice one, too. We did it every night, and made up a little song to go with it. I don't know that it is necessary, but brushing the gums can help make teething a little easier, and we've had wonderful luck because brushing teeth is something our son accepts and expects each night, and now he really enjoys it. After we brush his teeth, we let him brush his own teeth (he's now 16 months), and he loves loves loves it. Whenever he sees us brushing our teeth, now, he asks if he can brush his, too.