Dogs

Dogs don't grin on their own; they do it because they sense your enjoyment. Over the decades, man's best friend has evolved the capacity to pick up on indications provided by body language and respond in kind, even flashing people a pleased, tooth-baring grin. Canines in the wild expose their teeth to show hostility or fear. When they think you're about to throw a ball or give them a reward, they'll enthusiastically grin to indicate their delight and anticipation.

However, one of our most common companion animals needs as much or more dental care than people do, and vets are eager to help. Adult dogs have 42 permanent teeth, and more than 80% of puppies exhibit early indications of periodontal disease by the age of three.