Can a filler - such as juvederm change my smile shape? And will it look natural?

Thank you for your question. Yes, Juvederm can be used to help turn up the corners of the mouth and it cannot paralyze the muscle around your mouth. Juvederm can also be reversed and dissolved if you are unsatisfied with your result. It would be best to have a consult with a board certified dermatologist or plastic surgeon to evaluate your face to see where your issues lie so as to get the best correction to achieve the look you are wanting. 

Fillers can be used to turn up the ends of your smile.  The key is first to be evaluated by your cosmetic dermatologist or surgeon to figure out why it is turned down.  Strong pulling by the depressor muscles of the chin can cause a frown: that would be improved with injection of a botulinum toxin.  A frown appearance can also be caused by loss of fat of the cheeks making skin hang over the ends off the lips, loss of fat in the skin between the nose and upper lip leading to flattening of that area and/or loss of fat of the chin and jawline which means loss of support.  The choice, placement and amount of filler needed will depend on where your volume loss is most severe. Many patients need a combination in order to keep the look natural.  I hope this answer was helpful.  Wishing you luck!