I brush one of my dogs teeth twice a day, I started at eight weeks and he doesen't really care too much. My Lexi on the other hand hates it. I got her at seven and the previous owner did not take good care of her dental health. She gets a lot of bones and raw food, and occasonally (once a month or so) I chip the plaque off of them. There not great, but as long as they are not stained yellow everywhere or falling out I am not too worried.