Whitening treatments such as toothpastes, mouth rinses and teeth whitening gels act on the outer layer of the enamel to whiten the surface of the teeth. Teeth that appear stained due to previous pulpal infection do not respond to whitening treatments that only affect the surfaces of teeth. Internal bleaching is effective in most of these cases by whitening the tooth from the inside out. This method of whitening is applicable on a tooth that is endodontically treated. Upon completion of root canal treatment, bleaching paste is placed inside of the tooth to dissolve the stains, making the tooth appear whiter over the course of one to two weeks. While most cases respond to one time application of the bleaching material, some cases require two or three applications.