The subtle muscles of your mouth determine how you communicate in your environment.A dozen or so muscles connect with the circular muscle around your mouth (that’s just a fraction of those around your eyes). Some suck in the cheeks, others pucker the lips, or lift and lower them.A fire of a few neurons that instruct your mouth to move a certain way determine if you’re conveying rage, excitement, sarcasm, confidence, etc.Even smiles can be categorized by their beauty. The prettier the teeth, the more a person smiles. The more a person expresses emotion by using the facial muscles (around the eyes and mouth), the younger she looks.QUIZ: Is Your Face the “Artistic Ideal”?There are three classic types of smiles. Which type are you?The Mona Lisa (two-thirds of people):The mouth corners are pulled up and out. The upper lips raises to show the upper teeth. The most attractive show all their top teeth and about two millimeters of gums. Any more gums showing would make the smile appear gummy. The most attractive? Mona Lisa—with the upper and lower lips moving out half an inch and up to a 40-degree angle.The Canine (one-third of people): A particular muscle (called the levator labii superioris) is dominant and exposes the canine teeth before the full smile.The Full Denture (rare): All of the lower and upper lips expose all your teeth.As you get older, you can work to change your smile with facial exercises and taking care of your teeth. Your teeth get worn as you age, and as the soft tissue around your mouth descends to show your lower teeth instead of your upper. As teeth get shorter, this changes the tooth-to-gum ratio and gives a gummier smile.DISCUSS: How does smiling work for you?