Sir, the article Severe tissue damage and neurological deficit following extravasation of sodium hypochlorite solution during routine endodontic treatment (BDJ 2005; 198: 749) refers to a case where hypochlorite has extravasated and caused various problems. There is no indication in the article as to why the solution did extravasate although the discussion 'presumes' 'forced pressure irrigation led to entry of sodium hypochlorite into the soft tissues'. There is nothing in the article to back up that presumption and indeed the description of the practitioner using rubber dam would, if anything, indicate a reasonable and proper approach to endodontics.

I am therefore concerned at the use of the term 'misuse' in the précis at the head of the article, as hypochlorite irrigation per se is not misuse even if solution does extrude. It can happen accidentally and the references at the end of the article refer to 'inadvertent injection' 'hypochlorite induced' and 'caused by'. None of these terms indicate that, in the absence of evidence of improper use of hypochlorite, there is 'misuse'.

Although thankfully infrequent, there are regular problems of extravasation and I would not want to see a claim of negligence backed by this article implying that any case qualifies as 'misuse'.

It is too late to change the word or add further to the précis but I wonder if Witton and Brennan would respond in your letters page to clarify this matter in public.

Authors of the paper P. Brennan and R. Witton respond: We thank Mr Westbury for his comments about our report. Sodium hypochlorite solution is widely used in endodontic practice and fortunately complications are very rare. The main purpose of the paper was to document the previously unreported facial nerve involvement (resulting in upper lip weakness), to serve as a reminder to the dental practitioner of the possible severe complications that can occur when this solution extrudes into soft tissues, and to discuss the immediate management.

We would concur with Mr Westbury that this complication can occur accidentally, and indeed in the opening 'in brief' section at the top of the paper, our second statement was that 'accidents, while rare, can result in severe sequelae'. Although there was no conclusive evidence for the cause of the extrusion in the case presented, it would seem likely that the hypochlorite solution entered the peri-apical tissues under increased pressure. This assumption was made on the basis of normal apical anatomy being confirmed on radiographs and the severe nature of the presentation.

Each and every case of hypochlorite extrusion needs to be assessed and managed on an individual basis. With that in mind, we would certainly not wish this article to be used to back a claim for negligence for all cases of hypochlorite extrusion, especially as we wrote in our paper several times that this complication can be accidental in nature.

Interestingly, since our report was published, we have treated another patient with hypochlorite extrusion, which caused rapid severe life threatening airway compromise, requiring emergency surgical decompression. 1 Fortunately severe complications with hypochlorite extrusion are very rare indeed, with only a handful of publications in the world literature. We would reiterate that prompt recognition and referral is necessary to minimise the risk of further complications.