The outside are great, almost perfect. I like the way you draw the lips and nose from different angles. All i think can be improved is the inside of the mouth like the shapes of teeth and tongue. Anyway, really good techique!
Good afternoon, Ji-Sung, how are you? Welcome back to Line of Action. Greatest job on your rendering of the forces, forms, and details of the mouths and mouth shapes from all angles. Keep up the greatest work, indeed!
I'm not getting enough of the more dynamic and expressive mouth shapes, but the forms look or seem right-est to me. Would you like to free up your dominant and non-dominant arms with 1 hour of 30 second mouth and lip drawings? (120 mouth gestures) In addition to your control or understanding of the mouth, lips and teeth, then you'll use emotion and expression in your gesture drawings of those facial features. Your quick gestures will really make your mouth drawings and animations truly and truly come to life. Here's this link below. Good afternoon and good sketching practicing.
I think your understanding of lip structure has improved a lot and you are able to accurately capture the 3d shape in a simplifed drawing. For the teeth, I think it could be helpful to consider the indents in between each tooth after mapping the general line. Try more shading to practice seeing value. There are extreme dark and light points in the reference pictures that I would encourage you to notice. Don't be afraid of using dark colors! Great job practicing!