Sir, I read your interesting paper entitled 'Tooth whitening for the under-18-year-old patient' (BDJ 2018; 225: 19–26) in which you 'aim to provide readers with an understanding regarding bleaching protocols...' but find the section on management of discoloured traumatised teeth confusing and misleading.

You state that 'external' non-vital bleaching is best carried out by inside/outside closed bleaching but then comment that 'inside/open' approach is unnecessary due to rapid penetration of bleaching material through the tooth from the external surface.

For effective bleaching of discoloured non- vital root filled teeth the removal of cements, gutta percha and necrotic pulp remnants that contribute to internalised stain can only be addressed by open access when such an iatrogenic aetiology is diagnosed.

You mention 'associated risks' without consideration of external cervical resorption (ECR) which is a serious risk in non -vital traumatised teeth. The combination of bleaching and history of trauma is the most important predisposing factor for ECR.1

As part of a safe and effective bleaching protocol the literature indicates that it is essential to place a sound intermediate base over the root filling, reduced by 1-2 mm below the cementoenamel junction to prevent the ingress of bleaching agent and minimise the risk of ECR.1,2,3

Also without effective tooth bleaching protocols, shade regression is more likely and patients' expectations may be unmet.

The authors of the article, J. Greenwall-Cohen, L. Greenwall, V. Haywood, and K. Harley, respond:

Sir, thank you for your interest in our article. Our intent was certainly not to be confusing or misleading, so we appreciate the chance to expand on the comments concerning endodontically-treated teeth being bleached.

We agree with your comment and recommendation for access to the internal aspect of the pulp chamber and the need for a barrier after removal of 2-3 mm of gutta percha but did not include those details in this article but in the reference articles. 4, 5

The reason we say the inside outside open (IOO) technique may be unnecessary is that it carries no benefit over the inside outside closed (IOC) technique. The IOC ensures that the access cavity can be closed, minimising the risks associated with leaving the access cavity open, whilst the rapid diffusion of the bleaching agent from the external surface of the tooth still ensures rapid bleaching.

With regards to external cervical resorption (ECR), the literature on ECR was when high concentrations (30% or greater) of hydrogen peroxide 6 (HP) or sodium perborate 7 were used and when heat was applied. We are advocating the use of 10% carbamide peroxide (which is the equivalent of 3.4% HP) and no heat and as such, the risk should be considerably less.

We also agree that there are other predisposing factors associated with the ECR and bleaching, such as the history of trauma 8 that was highlighted.

A study by Heithersay 9 demonstrated that orthodontic treatment was the most important predisposing factor for ECR and bleaching. It is important to note that in these cases it is very difficult to determine if the root resorption was because of the bleach or the orthodontics/ trauma. ECR has been covered in detail elsewhere in this journal. 10, 11