Considerations for canal preparation – Mark Allen

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  Posted by: Dental Design      1st January 2019


In order to achieve endodontic success, effective shaping and cleaning is absolutely essential. As you know, that can only be achieved with efficient root canal preparation, in which all the organic debris and microorganisms are removed from the root canal system, and the canal walls are shaped to facilitate subsequent cleaning and obturation.

Failure to prepare all canals properly – the optive word being all, as missed canals is a common mistake in endodontics – could not only lead to problems later on in the treatment, but negatively affect the overall treatment outcome and long-term success. In the majority of cases (90%) root canal therapy is successful,[i]but as there is still a 10% chance that the treatment can fail it is important to consider all facets of canal preparation.

This includes technique and skills of course, as endodontic success is very much subject to an individual’s knowledge of what to do and abilities as a dentist. For simple to moderate cases, there is little reason why a general dental practitioner (GDP) would not be able to effectively prepare the root canal system, as it is covered extensively over the course of undergraduate education. However, in complex cases – for instance, where the canals are not visible, have been previously treated, start-mid way down the root, or have severe curvature – the skills required to carry out treatment are often beyond most GDPs’ skill set.

In such circumstances, patients would need to be referred to a specialist endodontist, but if you wanted to, there’s nothing to stop you from undertaking further training and education to improve your skills and become a specialist provider yourself. At least then you can rest assured that your scope of practice is extensive enough to deal with any patient that walks through the door with an endodontic complaint. Root canal preparation may only be one aspect of the endodontic process, but if your skillset is not extensive enough to deal with potential problems that can occur, the outcome could be severely compromised.

Naturally, the materials used can also affect the endodontic outcome, and in the case of canal preparation that means the type of file chosen. Historically, canals were prepared using stainless steel hand files, but since the introduction of rotary instruments made from nickel-titanium (NiTi) that have super elasticity and shape memory, practitioners have benefited from improved results. Some of the most notable benefits of rotary instruments are their enhanced ability to collect and remove debris from the canal system, reduction in time required for instrumenting canals and greater taper. Plus, because of their mechanical rotation, rotary files provide a more constant 360-degree engagement of the file tip in the canal so that they accurately follow the canal path. This also ensures better control, which helps to make sure that the central axis of the canal is maintained, thereby reducing the incidence of ledging or perforation.[ii]

Literature suggests that the downside of some NiTi rotary files is that when they are subjected to continuous structural fatigue, there is an increased risk of them fracturing in the root canal.[iii],[iv]It is thought that torsion and fatigue through flexure are the two primary causal factors of this,[v]with further research showing that the bending stress can be affected by the anatomy of the root canal. Naturally, the greater the curvature of the canal the greater the bending stress will be on the file.iv This is not the case with reciprocating files, which are believed to offer reduced torsional stress, less flexural stress on the file and a decreased risk of fracturing.iiIt is for those reasons that some practitioners choose to use reciprocating files over rotary instruments, however some believe that both methods are as predictable as one another.[vi]

Moreover, there is research to evidence that not all rotary files suffer from the same drawbacks. The HyFlexEDM 5thgeneration root canal files manufactured by COLTENE, for instance, have shown a significantly higher cyclic fatigue resistance and higher angular rotation to fracture than the reciprocating files they were tested against.[vii]This is thanks to the unique manufacturing process employed by COLTENE, which uses electric discharge machining to provide up to 700% higher fracture resistance than conventional NiTi files. Together with the controlled memory,HyFlexEDM rotary files reduce the incidence of the usual risks (and complications) of ledging, transportation and perforation and deliver predictable preparation – even in the most challenging curvatures.

Thus, careful consideration should be taken when selecting a file for canal preparation and an element of judgement and exploration is needed to ensure optimal results. Along with the right training, education and case selection, endodontic success should be within your grasp.


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[i]British Endodontic Society: Further Information. Accessed online July 2018 at

[ii]Sahu GK, Consul S, Nandakishore KJ, Shubhashini N, Geeta IB, Idris MD, Rotary Endodontics or Reciprocating Endodontics: Which is New and Which is True? J Health Sci Res 2016; 7 (2): 51-57. Accessed online July 2018 at

[iii]Sotokawa T. An analysis of clinical breakage of root canal instruments. J Endod 1998; 14: 75-82. Accessed online July 2018 at

[iv]Pruett JP, Clement DJ, Carnes DL Jr. Cyclic fatigue testing of nickel-titanium endodontic instruments. J Endod 1997; 23: 77-85. Accessed online July 2018 at

[v]van der Vyver PJ, Jonker C. Reciprocating instruments in endodontics: a review of the literature. South African Dental Journal. 2014; 69 (9). Accessed online July 2018 at

[vi]Dentistry Today: Rotary vs Reciprocation: “How do I choose?” Authored by John West and posted on 1 December 2017. Accessed online July 2018 at

[vii]Pedullà E et al. Torsional and Cyclic Fatigue Resistance of a New Nickel-Titanium Instrument Manufactured by Electrical Discharge Machining. Journal of Endodontics. 2016; 42 (1): 156-159, Epub 2015. Accessed online July 2018 at


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