Dogs are born with a set of temporary teeth, also called puppy teeth. There are 28 of these in total: 12 incisors, 4 canines, and 12 premolars.
When a puppy is about 3–6 months old, these teeth start to fall out, and then permanent teeth start to grow in. By about 7–8 months old, most dogs will have all 42 of their permanent teeth. These include:
12 incisors
4 canines
16 premolars
10 molars
Dogs do not grow a third set of teeth. If they lose an adult tooth, it will not grow back.