ABC Dentist: Healthy Teeth from A to Z by Harriet Ziefert, illustrated by Liz Murphy

From chapters.ca:
A trip to the dentist's office is easy once you know the ABCs of it. In this book kids will learn important words like "appointment" "cavity" "plaque" and "X-ray." Informative text and lively collage illustrations make this the perfect book to calm any child's fears about the dentist.

Open Wide! by Tom Barber

From chapters.ca:
Like many of us, Sam doesn’t like going to the dentist at all. Using a humorous approach, Open Wide! [may] help children overcome their fear of going to the dentist.

Dr. De Soto by William Steig

From chapters.ca:
Since he's a mouse, Doctor De Soto refuses to treat "dangerous" animals - that is, animals who have a taste for mice. But one day a fox shows up and begs for relief from the tooth that's killing him. How can Dr. De Soto turn him away? But how can they make sure that the fox doesn't give in to his baser instincts once his tooth is fixed?