The answer is, it depends. If dogs are young, you can estimate their age by observing which teeth have erupted.
For example, the deciduous incisors of a puppy usually erupt between 4 and 6 weeks of age and the permanent incisors are in place after 12 to 16 weeks. The canines or (canines) appear after 3 to 5 weeks and the permanent canines after 12 to 16 weeks. By the time the permanent molars are present, the dog is 4 to 6 months old.
In general, once a dog reaches the age of six months, all or at least most of its permanent teeth are visible.