All dentists must be licenced, and most hang their certificates in their waiting room. This shows the dentists has passed the certified education standard, and must to be visible to the patient. Dentists must also pass a yearly National Dental Exams to show they exceed the provincial standards. There are also 150 specialists in the province.
The best referrals are from friends, neighbors, and co-workers who are satisfied with their care. They source of referral may depend on the desired location of your dentists (close to home, close to work...)
You should also consider how a dentist charges for their services. Some will bill your company health plan directly, some require to pay up front, some even give discounts for cash or cheque (if you're not on a plan). Some dentists are taking the innovative approach of offering patients a flat monthly charge, regardless of work done.
And of course, check out the magazine collection in the waiting room. they indicate the type of clientele the dentist is currently dealing with. If it's filled with children's books, it may not be a great place for adults with a toothache to wait.