Smile with confidence, free of stains, discolorations or dullness. Liquid Smile Professional Whitening Pen is the first and strongest paint-on whitener available. This special hydrogen peroxide formula is 3 times stronger than all other paint-on whiteners, allowing you to achieve a whiter, brighter smile in no time. The neutral pH gel contains only the purest ingredients, for an effective and painless way to lighten your teeth. Root Beer flavor.