Personally I think it can't hurt. The frequency I think is dog dependent. My RB terrier had great teeth until be left us(he was 16) and we never brushed his, he just had periodic bones. Bear my aussie/pyranees mix has terrible teeth. We brush his using a human tooth brush and doggy toothpaste from Petsmart, give him bones, even use a pick to get some of the tarter off, and I still have to have a dental done by the vet about every 2 years!