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Dental Tribune United Kingdom Edition

April 9-15, 201216 Endo Tribune United Kingdom Edition R oot-canal retreatment is a very common procedure that endodontists and general practitioners are faced with on almost a daily basis. The biggest challenge here is to re- establish the initial pathway of the canal and its original exit or apex. During the past decade, several techniques required that gutta-percha be used to fill the root canals. Sometimes and for many reasons, such as leakage or short preparation and/or ob- turation, the gutta-percha needs to be removed and the canal re- negotiated. Generally, NiTi rotary files were used in such cases in or- der to facilitate and expedite our task. However, the files used to accomplish this task faced ad- ditional challenges, that is, the debris coming from the previous obturation and the density of the obturation material. The first dif- ficulty is piercing the mass of the obturation material. Here, our choice of file should focus on a strong tip that can take the pres- sure and engage the mass of the gutta-percha, break it down and pushitbackintotheaccesscavity. The second challenge is to select an instrument that can enter the root-canal structure and engage the obturation material, pushing it out coronally, while of- fering enough flex- ibility to go around curves and shape the root-canal surface safely. Today, thanks to heat treat- ment that has changed the world of rotary NiTi files, allowing us to modify the crystalline struc- ture of the metal, we have been able to obtain several types of the alloy to give us different files, from the Twisted File to the lat- est modification of the K3 sys- tem, the K3XF (SybronEndo; Fig. 1). The K3 system files are known to be robust yet very safe. The slight modification in their structure gives these files much-needed flexibility, while preserving their very high safety levels. The clinical applications are very simple. My favourite sequence of the K3 system is the G-pack, which allows me to do crown-down using the ta- per of the files and keeping the tip stable at ISO 0.25. This se- quence allows for a very nice start, removing the obturation material from the coronal third with relatively short files, such as orifice openers, and doing so in a relatively short time. The deeper we go, the more we need to decrease the taper, especially when curves are present inside the canals and smaller taper files are needed. It is at this particular mo- ment that the flexibility of the heat-treated alloy gives the files the ability to negotiate the curves without any distortion of the canal or macro-damage to the file structure (as has been demonstrated in research and clinically). Clinical cases The first clinical case could be described as a very bad day in a dental office. Two files had been trapped and separated in the me- sial canals and the patient was referred to the clinic but had to drive for more than two hours to When flexibility and strength are key Dr Philippe Sleiman discusses root canal treatments Fig 1 Fig 2 Fig 3