Maddie is now around 18 months and so far, has no plaque or tartar at all. I am using a product called Life For Teeth and Brush Away that is supposed to be amazing stuff. If your dog has tartar or plaque, using this will clean it up. If it is as wonderful as they claim, she will hopefully never have to have her teeth cleaned.
The Life for Teeth I spray in her mouth once a day and the Brush Away Gel I just use a couple of days a week. You can see before and after pics at their site and read testimonials. Here's the site:
http://www.petzlife.com/