Thumb sucking
Comforting and completely normal in a toddler. Past about four, the constant pressure pushes the upper front teeth forward and the lower ones back, narrows the upper jaw, and leaves a gap the front teeth cannot close — an open bite.
How we correct it: Encouragement and reminders first. If it continues, a fixed habit-breaking appliance behind the upper front teeth removes the satisfaction of sucking, and the habit usually stops within weeks.








