Intracoronal bleaching of endodontically treated teeth may be successfully carried out many years after root canal therapy and discoloration. The methods most commonly employed to bleach endodontically treated teeth are the walking bleach and the thermocatalytic techniques.
The walking bleach technique should first be attempted in all cases requiring intracoronal bleaching. It involves the following steps:
1. Familiarize the patient with the possible causes of discoloration, procedure to be followed, expected outcome, and possibility of future rediscoloration.
2. Radiographically assess the status of the periapical tissues and the quality of the endodontic obturation. Endodontic failure or questionable obturation should always be re-treated prior to bleaching.
3. Assess the quality and shade of any restoration present and replace if defective. Tooth discoloration frequently is the result of leaking or discolored restorations. In such cases, cleaning the pulp chamber and replacing the defective restorations will usually suffice.
4. Evaluate tooth color with a shade guide and, if possible, take clinical photographs at the beginning of and throughout the procedure. These provide a point of reference for future comparison.
5. Isolate the tooth with a rubber dam. The dam must fit tightly at the cervical margin of the tooth to prevent possible leakage of the bleaching agent onto the gingival tissue. Interproximal wedges and ligatures may also be used for better isolation. If Superoxol is used, a protective cream, such as Orabase or Vaseline, must be applied to the surrounding gingival tissues prior to dam placement.
6. Remove all restorative material from the access cavity, expose the dentin, and refine the access. Verify that the pulp horns and other areas containing pulp tissue are clean.
7. Remove all materials to a level just below the labialgingival margin. Orange solvent, chloroform, or xylene on a cotton pellet may be used to dissolve sealer remnants. Etching the dentin with phosphoric acid is unnecessary and may not improve the prognosis.
8. Apply a sufficiently thick layer, at least 2 mm, of a protective white cement barrier, such as polycarboxylate cement, zinc phosphate cement, glass ionomer, IRM (Dentsply/Caulk; York, Pa.) or Cavit (Premier Dental Products, King of Prussia, Pa.), to cover the endodontic obturation. The coronal height of the barrier should protect the dentinal tubules and conform to the external epithelial attachment.
9. Prepare the walking bleach paste by mixing sodium perborate and an inert liquid, such as water, saline, or anesthetic solution, to a thick consistency of wet sand. Although a sodium perborate and 30% hydrogen peroxide mixture bleaches faster, in most cases, long-term results are similar to those with sodium perborate and water alone and therefore need not be used routinely. With a plastic instrument, pack the pulp chamber with the paste. Remove excess liquid by tamping with a cotton pellet. This also compresses and pushes the paste into all areas of the pulp chamber.
10. Remove excess bleaching paste from undercuts in the pulp horn and gingival area and apply a thick well-sealed temporary filling (preferably IRM) directly against the paste and into the undercuts. Carefully pack the temporary filling, at least 3 mm thick, to ensure a good seal.
12. Evaluate the patient 2 weeks later and, if necessary, repeat the procedure several times. Repeat treatments are similar to the first one.
13. As an optional procedure, if initial bleaching is not satisfactory, strengthen the walking bleach paste by mixing the sodium perborate with gradually increasing concentrations of hydrogen peroxide (3 to 30%) instead of water. The more potent oxidizers may have an enhanced bleaching effect but are not used routinely because of the possibility of permeation into the tubules and damage to the cervical periodontium by these more caustic agents.