Which Tooth Brush is the Best for Children? Well, I usually say the one your child likes to use! That is, the one he is inspired to use properly and for a long enough time to get the job done. Basically, you can do pretty well with a regular plain toothbrush. There are not really any modifications that can overcome poor brushing technique. Yes, a smaller toothbrush for smaller children so it will fit their hand well. Also, softer bristles will do just fine. When you have braces, there are a few "orthodontic" brushes with altered bristles that might help.
Having said that, studies indicate that many kids do a little better job with battery-powered toothbrushes. You know the "spin brushes". There are a lot of battery-powered toothbrushes that are suitable for children. I would advise picking one that your child likes to use. You don't have to spend a lot on the fancier ones. Now if you are an adult, the Sonicare and Braun (expensive fancy toothbrushes) do a really good job and may inspire you!
Spin Brushes (very popular):
*Addendum February 2012: FDA warning spin brushes potential choking hazard:
I've never run into any problem, but I wanted everyone to know this potential problem.
Sonicare and Braun (they compete with each other fiercely):
I don't know what this is: