I have a bit of a witch's chin and a long chin, so I hated how my chin showed when I smiled, so I had T-bone surgery, but I regret it because I didn't know it was cool. My jawbone has definitely shrunk, but my chin has sagged, so it looks more prominent when I smile (especially from the side). I'm looking into muscle relocation surgery. But I also have a slight double chin, so my chin has gotten even bigger! Looking at YouTube, I heard that this is a common cause that can occur if the surgery is not done properly and the muscles are not removed well. If you want to have this surgery, make sure to find out if the muscles are realigned!