Mercer Mayer's very popular Little Critter is on his way to the dentist. It's a thorough check-up, complete with dental x-rays. When Dr. Ghum insists on filling a cavity, Little Critter goes through it bravely. The visit is painless to the reader because of Little Critter's funny, honest way of look at things -- including the world of dentistry.

Card catalog description
Little Critter goes to the dentist for a checkup, and finds that going to the dentist isn't so bad.

My son had me read this to him about 20 times. When he went to the dentist the first time, he wasn't scared one bit and seemed to enjoy it greatly.

In true kid fashion, he went from the dentist office to the barber shop where he went absolutely ballistic. My wife assured me that his reaction wouldn't have been worse had the barber placed blood-sucking leeches on him. The old, Italian barber didn't mind and reassured her that his grandson was much worse, but I digress.... Anyway my point is that this book worked for us, it might work for you if you think your kid might get scared at the dentist.