First the surface of the tooth is cleaned with pumice and the pretreatment tooth shade is recorded. The patient should be informed that the results of bleaching are not predictable and not guaranteed in all cases. Furthermore the patient is instructed as to the number of appointments and possible complications including cervical root resorption. Preoperative clinical photographs are helpful when demonstrating the change following bleaching to the patient.

Before commencing bleaching, a preoperative radiograph should be taken to assess the existing quality of the root canal filling and status of the peri-apical tissues. Under no circumstances should bleaching be undertaken if there are any concerns with regard to this. Root canal retreatment should be carried out when in doubt and the filling material allowed to set at least a week prior to commencing intra-coronal bleaching (Figs. 18.1 and 18.2).

Rubber dam should be used to isolate the tooth in question. The access cavity is prepared, and all coronal remnants of restorative material, root filling materials and necrotic pulp tissue should be completely removed. In the anterior teeth, it is important to incorporate the mesial and distal pulp horns in the access cavity design and ensure that these areas are ultrasonically prepared to remove any remnants.

The root filling should be reduced 1–2 mm below the cement-enamel junction (CEJ). This can be determined by using a periodontal probe placed in the pulp cavity and comparing to external probing depths to the CEJ. The root filling should be sealed with a base (IRM or glass ionomer cement) of at least 2 mm to prevent diffusion of bleaching agents from the pulp chamber to the apical foramen. This sealing material should also reach the level of the CEJ to prevent leakage of bleaching products into the surrounding periodontium resulting in increased risk of external cervical root resorption. A radiograph can be taken to confirm that this step is correct (Figs. 18.3 and 18.4).

The pulp chamber is etched with 37 % phosphoric acid for 30–60 s, washed and dried. This allows opening of dentinal tubules for penetration of bleaching agent (Fig. 18.4).

Sodium perborate (Bocasan) is mixed with distilled water in a ratio of 2:1. The bleaching agent can be applied with a suitable carrier or plugger (Fig. 18.7).

A small piece of dry cotton wool is placed over the bleach and the cavity sealed with either IRM or glass ionomer cement. The patient is reviewed on a weekly basis and the process repeated until the tooth is slightly overbleached. Usually successful bleaching will become apparent by 2–4 visits.

Once bleaching has been completed, the access cavity should be restored with a resin composite which is bonded using an acid etch technique. Optimal time for bonding is usually 3 weeks following completion of bleaching. An interim dressing of calcium hydroxide is recommended during this time period to prevent any bacterial penetration and minimize further the risk of cervical root resorption (Fig. 18.5). A final postoperative clinical photograph should be taken to record colour changes achieved.