7
FOCUS ON
Endodontic files: parameters for selection and reuse Eugenio Pedullà, who was involved in development of a new endodontic files system, suggests giving preference to flexible, pre-bendable instruments and provides guidance for the possible reuse of the files
Eugenio Pedullà
Over the last few years, increasing numbers of canal preparation instruments have been introduced on the market and working out the most appropriate instrument to use depending on the clinical cases in question is not as simple as it seems. "Clearly, not all endodontic files are the same," explained Eugenio Pedullà, an Associate Professor at Catania University in Italy, who was involved in coming up with a new system for Coltene HyFlex EDM endodontic files. "We have now reached the seventh generation of endodontic shaping instruments made from titanium, as reported in a recent review on this subject in the official journal of the European Society of Endodontology. It is essential for dentists to have an awareness of the various possibilities offered by these files, or at least the main ones, in order to make the best and correct use of the properties of the instrument that you have decided to use."
Professor Pedullà, what parameters should be used to guide the choice of endodontic files?
There are many parameters that influence the characteristics, and especially the mechanical characteristics, of nickel-titanium endodontic instruments. The two most important characteristics are the dimensions of the instrument, and particularly the taper and the heat treatment applied to the NiTi alloy. These two parameters do in fact have a significant influence on the flexibility of endodontic instruments. A heat-treated instrument has greater flexibility than an identical instrument made from traditional NiTi. This increased flexibility will, however, be greater in the case of some heat treatments than others. As widely reported in the literature, CM (controlled memory) heat treatment is the one that provides the greatest flexibility. As far as the dimensions are concerned, just bear in mind that the smaller the files are, the greater their flexibility, given the smaller amount of metal present. Of the two main parameters relating to the dimensions of endodontic instruments, the tip diameter and the taper, the latter is the one that has the greatest influence on the characteristics of the instruments, as it influences the size of the whole working part of the file and not just its tip. Thus, a 30.04 instrument will be more flexible than one that is identical but 25.06.
What materials were used in the past?
For a very long time, root canal preparation was carried out using instruments made from steel, a very rigid metal which has a hard time following the often curved anatomy of root canals, frequently causing transportation. From the 1990s, the introduction of NiTi provided instruments with larger dimensions but which retained a high level of flexibility, with better adaptation to the original anatomy and, at the same time, made it possible to achieve appropriate dimensional preparation with a smaller number of instruments, speeding up endodontic therapy. The introduction around 2007 of heat treatments applied to NiTi subsequently improved the flexibility of endodontic instruments and consequently provided better adaptation to the anatomy.
Interview Prof Eugenio Pedullà, Dental Journal Italia, 01 July 2024 (File endodontici, parametri per la scelta e per il riutilizzo (dentaljournal.it)
PARAMETERS FOR SELECTING ENDODONTIC FILES • Preferably use flexible or pre-bendable instruments for cases involving curved anatomical features, and an instrument that is a bit less flexible as well as at least one that is at least slightly pre-bendable for narrower canals. • Always have pre-bended instruments available in any case, even if only to enable easy insertion in cases where access is too complicated for anatomical reasons, or the patient has limited mouth opening. • Always perform early crown lengthening (in the correct manner, i.e. without lengthening it beyond the first 5 mm and obtaining a slightly smaller opening size than you will achieve by the end of the preparation) and create a glide path before carrying out the actual canal shaping using larger NiTi instruments. • Seek to perform conservative shaping using a .04 taper file but complete the preparation to at least 30 as the tip diameter. Furthermore, using a CM heat-treated instrument with a .04 taper enables smoother, more comfortable apical shaping. • Where possible, reuse the files in an endodontic system; while this depends on multiple variables, I generally recommend reusing files (check for integrity and any deformation beforehand) for two molars at most (approximately 6 root canals) and sometimes only one (3-4 root canals), especially in the case of smaller instruments such as glide path files.