Please, read up on vet sites, check the links I posted Buddy's Pal. 
Well they actually suggest routine checks at least yearly, cleaning if needed. When I fed raw, my dogs, never a one, ever needed their teeth cleaned. And the vet felt Cara's were fine last year, but who knows in Feb.. she may need them cleaned (she'll be 3). If you make brushing a routine, you may not have to have it done. But because of Arwen's autoimmune disorder, hers have to be cleaned every 3 mos as she reacts to plaque even tho there is almost no tartar on them at cleaning time. 😞
So I had to go look at the stats and info. The only ones I find are like this, examine teeth, clean if necessary. But if 80 percent have issues by 3, then they probably need scaling before unless you are brushing regularly.
http://now.tufts.edu/articles/dental-disease-cats-dogs
::::: Equal Opportunity Bacteria
Some 80 percent of dogs and 70 percent of cats show signs of oral disease by age three, according to the American Veterinary Dental Society. However, problems can start at a much younger age. “I have taken puppy or kitten teeth out of animals that are six or seven months of age, and there is already tartar buildup,” notes Rosenblad, who teaches veterinary dentistry at Tufts and is president of the Veterinary Alumni Association.::::::
