Yes, our product works on crooked teeth as well. Our mouth tray is a non-moulding universal tray which is designed to fit our Whitening LED Light and cannot be modified. The tray is designed to stop your lips and saliva from removing the gel from the surface of your teeth. Once inserted simply apply pressure to the front of the tray and it will make contact with the surface of your teeth, you can then let go and the gel will stay on the surface of your teeth even though the tray is not making direct contact. You can also use our Whitening Pen to apply the gel directly onto your teeth to make sure that the surface is covered and then insert the tray and light as per normal.