Some people show a lot of their gums when they smile. This may be due to several reasons. An upper lip that is short may not drape over the gums sufficiently. Excessive growth of the maxilla in the vertical direction results in the upper dentition being carried further down beyond the coverage of the upper lip, particularly when smiling. They end up showing a lot of teeth and gums when they smile. Protrusion of the upper front teeth also makes it harder for the upper lip to drape over them. Sometimes, the gums surrounding the teeth do not recede at a normal pace with age, resulting in a display of more gums and less teeth (i.e. shorter crowns) when smiling. Depending on which factors are at play, treatment may involve gum surgery, orthodontic treatment, jaw surgery, or a combination these.
See also: Protruded lips