The following is a response by author Virat Hansrani to two letters regarding a BDJ paper he authored entitled Assessing root canal fillings on a radiograph – an overview (BDJ 2015; 219: 481–483). The first letter is entitled Endodontics: Gross misinterpretation (BDJ 2016; 220: 90) and the second entitled Blatant ignorance (BDJ 2016; 220: 90 91).

The author Virat Hansrani responds to the above letters: I thank the authors of these two letters for their comments. The main cause of concern in this article stems from the rather general title, which in hindsight may not have helped. However, the detailed abstract should have cleared any confusion in understanding the learning objectives of the article, which I feel have been misinterpreted.

One objective of the article, as per the abstract, was to 'discuss why a root filling that appears satisfactory on a radiograph may fail, and why one which appears unsatisfactory on a radiograph may succeed.' Perhaps this would have been a better title. Other objectives were to discuss the criteria of endodontic success and failure and its implications on the decision to re-treat.

I acknowledge the concerns regarding the European Society of Endodontology (ESE)1 guidelines. According to these, when assessing the outcome of root canal treatment, root canal treatment has either a favourable outcome, uncertain outcome, or an unfavourable outcome and there is an exception too. More detailed and accurate ESE guidelines for an unfavourable outcome are (1) the tooth is associated with signs and symptoms of infection; (2) a radiographically visible lesion has appeared subsequent to treatment or a pre-existing lesion has increased in size; (3) a lesion has remained the same size or has only diminished in size during the four-year assessment period; (4) signs of continuing root resorption are present. I acknowledge the idea of anachoresis is an outdated theory.

Comments to Jivraj et al.: I acknowledge that no reference was made to cone beam computed tomography, and its usefulness could have been included as an adjunct to radiographs. The following examples provided by Ng et al.2 which were not discussed in my article, can also provide reasoning behind why a radiographically successful root filling may fail and why a radiographically unsuccessful root filling may succeed: absence of a pre-operative sinus tract, achievement of patency at canal terminus, extension of canal cleaning as close as possible to its apical terminus, use of ethylene-diamine-tetra-acetic acid (EDTA) solution as a penultimate wash followed by a final rinse with NaOCl solution in secondary RCT cases and absence of tooth/root perforation. It is important to understand that some of these examples Ng et al. provided are visible on a post-operative radiograph (canal cleaning as close as possible to canal terminus) and others are not (use of EDTA). This was the key theme running through the article, and advice was provided to help clinicians elucidate under what conditions the root filling was conducted.

I understand why Jivraj et al. feel the article could mislead the readers into thinking that obturation is of no significance. To remove this concern, we must re-refer back to the abstract and learning objectives of the article. One objective was to discuss why a radiographically unsatisfactory root filling may succeed. This article identifies obturation as being one of few features visible on a post-operative radiograph, and thus states that other features which are integral to a successful root filling, may not be visible on a post-operative radiograph. For example, the quality of disinfection. At this stage, I must state that a good quality obturation is a major contributory factor to 'success' and I was not trying to diminish its importance; rather stating that there were other features during root canal preparation which are also contributory to the success even though they are not visible on a radiograph.

Comments to Chong et al.: I acknowledge that the interchangeable use of periradicular periodontitis, periapical periodontitis and apical periodontitis may lead to confusion amongst readers. At the time of writing this article, I did not have access to sufficient clinical exposure to take my own radiographs, hence they were referenced from another BDJ article. I appreciate that I could have included in the figure legend that one radiograph (Fig. 2) presented in the article did not meet the ESE guidelines and the other two radiographs (Fig. 2 and Fig. 3) were diagnostically acceptable.

The authors made reference to Di Filippo et al.3 who assessed the quality of root fillings as adequate or inadequate based on ESE guidelines.1 Di Filippo found inadequately root filled teeth were associated with apical periodontitis in 68.6% of cases compared with 14% of cases with adequately root filled teeth. My article discusses why these adequately root filled teeth may have failed and why the inadequately root filled teeth succeeded.

Overall my article made no claim that canal obturation was not required. I understand that it is a major contributory feature in the success of root fillings. I was discussing why root fillings, which may look satisfactory on a radiograph, can fail and why some root fillings which look unsatisfactory can succeed. In doing so, I was discussing which features important to the success of endodontics are seen on a post-operative radiograph and which are not seen on a post-operative radiograph.

I would like to thank all the authors for taking the time to read and so thoroughly provide their feedback on my article. This has been very instructive to me for my future work and I hope, thanks to the open stance of the BDJ, also demonstrates the value of frank opinion sharing in ongoing peer review in scientific publishing for the benefit of all.