Sir, thank you for your recent series of articles on endodontics. I found them fascinating and informative. I have been in practice for more than 30 years and after reading only the first two articles, I changed my views, so much so, that I have completely embraced this technique and have yet to have a failure.

I am led to believe that the average Streptococcus Viridans is about one micron in diameter. With this in mind I began wondering about the nature of apical obturation, since how can we be absolutely certain the canal is sealed? Also, bearing in mind the possibility of lateral canals, indeed the certainty of their existence, are we not in a similar position to the farmer trying to keep harvest mice out of his cornfield with hedges instead of a solid steel wall?

This analogy shows that Dr Carrotte's series of articles are bang on the money, in that access and complete disinfection of the canal is paramount. I also feel that we can give ourselves a false sense of security when we review a root filling with a post operative radiograph showing the filling to the apex, if this therapy has not included a thorough debridement, and a copious irrigation of the canal with sodium hyperchlorite.

If the observations on the size of bacteria are correct, do radiographs really tell us if we have reached the apex? Let's say we are 1/100th of an inch short, could we really detect this on an ordinary periapical, chemical or digital, even with a decent amount of magnification? Bringing the microorganism to a human scale, this distance would roughly equal the Mersey Tunnel and how many people could stand in that?

In addition, it has long been my belief that x-rays travel in straight lines, and because of this, the following scenario is possible. Figure 1 shows an ideal root canal filling (RCF) in an upper incisor with the beam passing through the root in a bucco-palatal direction. Figure 2 shows a similar tooth, but this time the RCF is approximately 1mm short of the apex. Figure 3 shows the same tooth but this time the beam travels in the mesio-distal direction. Quod erat demonstrandum! Sometimes I really wish I had the same optical capabilities as superman!

figure 1

Figure 1

figure 2

Figure 2

figure 3

Figure 3