Brushing your dog's teeth daily helps remove bacteria, plaque and debris and is a great addition to pet health care. Dogs don't get cavities, but they do get periodontal disease, and brushing helps prevent this. (So do chewing on raw bones). The appropriate toothpaste to use is a pet toothpaste that has enzymes to control plaque.
The use of fluoride in pet toothpaste is controversial and most veterinary dental specialists and general practitioners don't recommend its use because of the potential problem of toxicity. Human toothpastes can have higher levels of fluoride, as well as salts, detergents and baking soda that can harm your dog's teeth.
Don't forget that people rinse after brushing, but dogs just swallow the toothpaste. An overdose of fluoride can cause vomiting and at higher levels can lead to kidney damage. The fluoride builds up in the body over time.
Why are there pet toothpastes with fluoride? Because it appeals to the consumer, and it sells. Someone is profiting at the expense of your pets health! Please don't buy toothpaste with fluoride for you or your pet. It is a toxic chemical.