Teeth whitening, is either the restoration of a natural tooth shade or whitening beyond the natural shade. Restoration of the underlying natural tooth shade is possible by simply removing surface stains caused by extrinsic factors, stainers such as tea, coffee, red wine and tobacco. The buildup of calculus and tartar can also influence the staining of teeth. This restoration of the natural tooth shade is achieved by having the teeth cleaned by a dental professional, or at home by various oral hygiene methods. Calculus and tartar are difficult to remove without a professional clean. To whiten the natural tooth shade, bleaching is suggested. It is a common procedure in cosmetic dentistry, and a number of different techniques are used by dental professionals. There is a plethora of products marketed for home use to do this also. Techniques include bleaching strips, bleaching pens, bleaching gels and laser tooth whitening. Bleaching methods generally use either hydrogen peroxide or carbamide peroxide which breaks down into hydrogen peroxide.