TWISTING AND PULLING
Step 1:
Select the Liquify filter. The dialog opens with a preview in he center, tools to the left and tool options to the right (use the Size, Pressure and Jitter options to control the effects of the tools). Broaden the subject's smile by selecting the Warp tool and dragging the edge of the lips sideways and upwards. Make the brush smaller if too much of the surrounding detail is being altered as well.