Although he's not super-local, I believe the dentist of my childhood is still practicing in Concord, MA. I can't find a website, but contact info is here.

They were really good at explaining and talking to kids, and willing to do any number of silly things to make it all okay. (Once, he did an entire exam on a kid with the kid upside down.) Also, when I was there, they had adorable little white dogs who would sit on your lap, although they were quite old by the time I was in high school!