Before the reconstruction of a root canal-treated anterior tooth, the walking bleach technique should always be considered.
In the past, a lot of root canal-treated teeth were routinely reconstructed with metal posts and crowns. Today, more conservative strategies such as internal bleaching, fibre posts, composite restorations or minimally invasive porcelain veneers represent alternative treatment options (Zarow et al, 2009).
In the case of porcelain veneers or crowns used in order to mask the dark colour of the tooth, the dental laboratory requires more tooth reduction, which significantly reduces the mechanical and adhesive properties of restorations. For longevity of porcelain veneers, the presence of enamel is crucial.
The less enamel used, the lower the adhesion value of the porcelain veneer is to the tooth structure, making the final veneer restoration less predictable. Therefore, instead of reducing the tooth structure, the aim should be to try to change the colour as much as possible by bleaching internally (Meyenberg, 2006).
If the treatment plan includes a prosthetic crown, the aim of internal bleaching is to improve the colour around the cervical area and coronal portion of the root. These details will determine the final aesthetics within the gingival area. The walking bleach technique is therefore the procedure of choice in such cases. The protocol of internal bleaching was carefully described in the literature (Plotino et al, 2008; Nutting and Poe, 1963; Zarow, 2016).
The most popular and safest material for this purpose is still that which has been used routinely in clinical practice for several decades. This is a paste, prepared ad hoc, composed of sodium perborate and 3% H2 O2 or distilled water. (Editor’s note: EU legislation has banned the use of sodium perborate due to its foetotoxic and cytotoxic properties [Scientific Committee on Consumer Safety, 2010].)
This article presents a case report of the aesthetic treatment in a case of a severely discoloured root canal-treated tooth, where there was a contraindication for internal bleaching.
Contraindications for internal bleaching
The most important factor in bleaching effectiveness seems to be precise removal of all restorative materials from the access cavity without additional dentine elimination.
Dentine has to be cleaned in order to facilitate diffusion of the bleaching agent through the dentinal tubules (Plotino et al, 2008; Zarow, 2016). If a fibre post was cemented in the root canal and the pulp chamber was filled with composite resin, removing the restorative material and post can compromise the amount of sound dentine. Therefore, such a case calls for careful evaluation of aesthetic benefits versus structural sacrifice.
Other contraindications for internal bleaching include (Madison and Walton, 1990; Rotstein et al, 1991; Lado et al, 1993; Buchalla and Attin, 2007; Lin et al, 1998; Zarow et al, 2013; Baba, 2013):
Discolourations caused by amalgam or other metallic materials (not bleach-able)
Significant dentine loss in the cervical portion (risk of fracture and leakage of bleaching agent)
Visible cracks, especially with subgingival extension (risk of bleaching agent penetrating towards periodontal ligaments)