A gummy appearance can be caused by several different things such as ratio of your gum relative to your teeth length, how worn your teeth are, as well as your skeletal shape, etc . Different issues requires different solutions.
If the ratio of your gum relative to your teeth is too long, the solution is either to make the teeth longer, or the gum shorter. The dentist will evaluate your teeth and gum carefully and determine the correct strategy. If the gum is deemed excessive, a gingivectomy is performed to reduce the length of the gum thus enhancing your beautiful smile.