Yes, start as soon as you can, the earlier the better, because, they get used it from a young age and are more likely to let you do it if you start young, also there is less chance of teeth and gum problems if you brush early rather than later. I brush both my guys teeth and I bought a toothbrush kit from Petsmart, you can buy them at any pet food and dog supply store. It comes with a toothbrush , a finger cot toothbrush, and beef or chicken flavoured toothpaste. You don't really needed to use toothpaste, as its the actual brushing that cleans the teeth, not the paste, the paste just gives a flavour, so the dog may be more apt to like it, but may just eat it. Lol. It's the same for people, the toothbrush is what actually cleans the teeth not the toothpaste , toothpaste,just gives you a nice taste and a feeling of fresh breath, but you could just use water, or baking soda to clean your teeth.