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ePaper created 2016-11-22, 09:52:12 | version 1.38.0
canal shaping case report | 29 roots 4 2016 present in the distal and in the mesio-buccal canals. In a case like this it is important to redefine the shape ofthepreviouspreparationandfirstandforemostan endodontic file system is needed that is flexible and prevents further unproportional loss of tooth sub- stance. For the canal preparation a renowned nickel tita- nium file system by Swiss dental specialist COLTENE (Fig. 2) was used. Thanks to a clever combination of unique material properties, pre-bendable HyFlex CM files are virtually unbreakable. The reason for this phenomenon is simple: the well-known “Controlled Memory”-effect is flexible enough to find its way around the distorted canals. It improves certain physical qualities of the alloy itself. Similar to classi- cal stainless steel files the instruments can be pre- bent, but they do not bounce back like conventional NiTi files. This typical characteristic makes “CM”- treated NiTi files extremely flexible. Highly versatile files are particularly helpful if you have to move around abrupt curves or—in this case—a mutilated anatomy. After usage their form adaptation can be quickly reversed in the sterilization process. During autoclaving the instruments turn back to their origi- nal shape (Fig. 3). The refined NiTi files are very resis- tant to cyclic fatigue and can be reused safely, as long as they are not plastically deformed. The Hyflex CM-files respond to excessive resis- tance with straightening of the spirals, which avoids bindingtothewalls.Tocreateanyformofstepsinthe canal shape is incredibly hard and instrument sepa- ration is almost impossible, as long as the files are applied correctly. A good preparation technique is to move the file in a soft pecking motion through the canal. In addition to that it is highly advisable to irrigate the canal thoroughly every time a file in the sequence is changed. Once the manual glide path was created, it was veryeasytobypassthevariousstepsandledgeswith thepre-bendableHyFlexfiles(Fig.4).Themechanical rotation was started on the endodontic motor only after the insertion of the pre-bent instrument in the canal beyond the step. By this approach the risk of perforation is generally eliminated and no further damageoftherootcanalwalltakesplaceatthelevel ofthestep.Beyondthestepweusedtherotatingfiles as usual at the normal operating mode of 500 rpm. With only a few files per canal it was possible to in- strument the root canal up to a working length of 21 mm. The mesio-lingual canal was finally instru- mented with a pre-bent .35/0.06 file (Fig. 5). The file was inserted into the canal with two to three subtle movements, then withdrawn before it re-entered the canal. Similarly, the mesio-buccal canal was shapedwithasize.35filewithataperof0.04(Fig.6). Toenlargetheapicalaspectofboththedisto-lingual and the disto-buccal canal a 45/0.04 file was used (Fig. 7). All files kept their pre-bent shape during the pro- cedure and moved safely in the centre of the canal. Even unexpected angles could be managed almost effortlessly with the swift moving instruments. De- spite the numerous steps that got sculptured into the root canal before a smooth shape was finally re- gained, which would ensure a tight and reliable ob- turation of the root canal system (Fig. 8). Fig.3: Refined shape memory of“CM” – treated NiTi files. Fig.3 42016