Try a pediatric dentist-- they specialize in children and generally they (and their office) are more 'kid friendly' than General Practice Dentists. You can also get him used to the idea by talking about what the dentist does, read books about it, watch a dvd (i think Blues clues had Blue going to the Dentist), and try roll playing-- where you are dentist and let him be dentist to you.
Also-- some kids need to 'warm up' to the office, so if your child does not have any dental problems you could work up to an exam visit-- like 1st time let him look in the room, next visit sit in the chair... and eventually he will be comfortable enough to have the exam done. (I did this with my 2nd and 3rd they were very apprehensive about the dentist).
at 3:35 PM on Apr. 13, 2011