A gummy smile as you correctly described is one in which there is excessive show of the upper gums during smiling. This can be caused by dental issues, overactive facial muscles or thin lips.
The main culprit when we talk about overactive/strong facial muscles is the LLSAN (Levator Labii Superioris Alaeque Nasi). This muscle lifts the upper lip and also helps you scrunch the nose up. To correct the gummy smile, one would use botulinum toxin to target the inferior portion of the muscle (just adjacent to the nostril) to weaken it temporarily.
The muscles around the mouth the Orbicularis oris are responsible for pursing the lips, and this causes inward rolling of the lips during smiling and giving the appearance of a thinner, less full upper lip. Botulinum toxin can be injected here to reduce this effect.
The results can last 4 to 6 months depending on the individual.
Another possible cause would be thin lips that are lacking in volume. In my experience filler injections with Juvederm Volift or Volbella can add volume to plump up the lips. The effect of the filler can last up to 1 year.
I hope this addresses your concerns.
Regards
Dr Mark Lim
