Teeth Whitening Pens Best Overall: Teeth Whitening Pen 35% Carbamide Peroxide · Best Natural helpful in the maintenance of whiteness of the teeth. Whitening pens take from 2 days up to a week until you notice results. After a thorough brushing, remove the top cap of the pen and twist the bottom of the pen until you see the gel on the brush tip. Then, apply a thin layer of whitening gel to each tooth's surface, making sure the entire tooth's surface is in contact with the whitening gel. Finally, don't rinse. Wait on hour before eating or drinking .