Gummy smile is a condition in which there is excessive display of the gums covering the upper teeth. The muscle that controls movement of the upper lip could be hyperactive causing the upper lip to rise up higher than normal, especially when you smile.
The optimal smile line should reveal the least amount of gum tissue possible. The excessive gingival display can make smile less attractive, often causing reluctance to smile at all.
This condition can be helped with botulinum toxin injections. The effects last for around 3 months, gradually wearing off. Repeated timely administration of botulinum toxin injections will extend the period of effectiveness, due to the lip elevator muscle learning to adapt.