In the past it was mandatory to visit the dentist every 6 months, in order to be covered by health care insurance. Nowadays it's not mandatory, but dentists still hold on to that interval (they earn money by doing so, of course).
I'm wondering what the guidelines in other countries are, do you get multiple checkups in a year or only every two years or so? I just realized that I didn't go for four years (busy schedule, time flies) and went to the dentist who said my teeth and gums are in perfect condition (and she wished everyone would floss and use toothpicks). Still she recommends to come back in 6 months?