A nice smile is an important component of facial aesthetics though not many surgeons pay much attention to this.
There are some features which may contribute to a not so nice smile eg gummy smile.
Different factors contribute to the problem, which may be corrected by orthognathic surgery (if upper jaw is too long), dental ( teeth and gums) surgery to shorten upper lip or toxins to the lip muscles. Only with proper assessment can the problem be corrected.
Toxins injection to lessen gum show