My son has been going for regular check-ups since he was 2-1/2 (he's now nearly 4) and my daughter had her first visit at age 2. My daughter wasn't interested in opening her mouth for the dentist, so he showed her around the office and the dental chair.
In the States, it is recommended that children begin seeing a dentist once his/her teeth erupt, in order to both ensure good oral hygiene and accustom the child to the dentists' office to set the stage for a lifetime of good dental care. Most people I know there start sending their children to the dentist between the ages of 2-4. The dentist we see here said that he recommends that children begin going between the ages of 3-5.
It is imperative to me that whichever dentist we see is relaxed with children and doesn't pressure them unless absolutely necessary. My son loves going to the dentist (!) and my daughter came away from her first appointment with a positive impression.
Good luck in whatever you decide!