Can foods can soften their teeth, potentially cause gum disease, and increase plaque and tartar buildup.
Canned dog food is better for dogs missing chewing teeth, but in general, it's not ideal to feed your puppy or dog only canned dog food. If you opt to do this, you'll need to provide plenty of crunchy things for him to eat, as well as more teeth cleanings.
Canned food is better in regards to crude protein, moisture, and sometimes fat content, but in regards to teeth and gums, it's ideal to offer dry kibble. Can blended with dry is ok, but a diet of only can food isn't ideal for teeth health.