Where, why, how to prevent and what to do in case of fracture of rotating instrumentarium
Where do NiTi files break?
They break in narrow, bent canals. In the picture below these are the red radices. The mesial canals of the lower molar are notorious.
Why do they break there?
Because these canals have sharp bends from buccal to lingual which are not or hardly visible on an X-ray. Mostly they are somewhat oval canals (both positioned in the same radix), so that a rotating file in a stricture easily jams and breaks.The mesiobuccal canals (MB1 and MB2 of the upper molar usually have such a bend as well, so that both canals come together apically. This too is very hard to see on an X-ray.
How can fracture be prevented?
Before preparing until working length with a Rotary file, a hand file 015 should at least have been on working length. Then, it is necessary that the NiTi files are active on a limited part of the canal. For that reason it is wise to start crown-down from the pulp chamber with a bigger file and then to prepare with a smaller and smaller file some millimetres further to apical. You could start with Profile 06 Nr 40, then Nr 35 to Nr 30 and as a last one No. 25. In between Gates Glidden Drills, which only get smaller in the coronal part, can contribute to prevent fracture. It is also important that the pulparoom pulp chamber is filled with Natriumhypochlorite. Also, the use of lubricants like Glyde helps to prevent fracture. The files should – of course – be used sparingly. Should the files be used a lot, they would eventually break. Even if you carefully check the files as to diswinding, there is absolutely no guarantee that the file will not break.
How can a part of a NiTi file be removed?
See the chapter Removing broken instruments and look at the film below.
(Attention, the file’s size is 1.3Mb.)
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Filling the canals
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The endodontic retreatment
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