TOOTH DISCOLORATION is a challenge that many dentists face, and internal bleaching is a practical treatment option. Internal bleaching is used to lighten a discolored tooth that has had root canal therapy. It involves placing a chemical oxidizing agent within the coronal portion of a tooth to remove discoloration. The etiology of tooth discoloration can be intrinsic, extrinsic or both; it can involve dentin, enamel or pulp; it may be brought on by diet, age or habits; it may be local or systemic; and in some cases it may be iatrogenic. Discoloration can be caused by endodontic filling materials or medications that the patient is taking. Discoloration associated with pulpal involvement can be caused by intrapulpal hemorrhage (in which case it is pink or brown), necrotic pulpal tissue, secondary dentin formation (in which case it is yellowish), and internal resorption (in which case it is a pink spot).