I have had lip corner filler twice, once only at the corners of the mouth, and once at the lips + mouth corners together.
Even after getting it twice, I am not really sure whether it was effective .. (they said no one really noticed any difference) I was told that the problem is the muscles used at the corners of the mouth, so getting filler would not greatly improve it, but would just help the corners lift when smiling??
Anyway, I did not see much effect, and when I spread my teeth apart like this ~, my lower teeth did not open properly. I wonder if that was a side effect .. Anyway, it was uncomfortable, so I did not do it again after that!