Gummy smile happens when muscles lifting the lip are overactive causing you to show more teeth when grinning or saying certain words. Some people are expressive with their mouth and exaggerated upward lip curling is a worry for them. When one smiles they activate lip elevator muscles. At our Cosmetic Clinic inDublin, toxin injections is aimed to relax those muscles so they can’t lift the lip as vigorously as the non-treated muscles.