In order to fully understand the current techniques for canal preparation, it would be beneficial to look briefly at previous methods, and the associated problems which led to further development. Interestingly, in 1933 a paper was published in the dental literature recommending the use of maggots to consume and remove the necrotic larger instrument is then inserted 1.0 mm less into the canal so that a taper is formed. In between placing each larger instrument, the master apical file is inserted to the working length to clear any debris collecting in the apical part of the canal; this is referred to as recapitulation. The stepback technique helped to overcome the procedural errors of the standardised technique in slight to moderately curved canals, but in the more severely curved root canals problems still exist. There are three ways in which some of the problems of the curved root canal may be overcome, by using:
A special filing technique. A file with a modified non-cutting tip. More flexible instruments.