The file is rotated 60 degrees clockwise in the canal when a slight resistance is felt. įiles used for this technique need to be non-cutting edge and flexible. This is the most widely used technique and especially good for working with curved canals. This allows the file to effectively debride the canal dentine by moving slowly down the canal.įor K-type files, once the file has reached the desired working length, a push and pulling action is used around the circumference of the canal, while only maintaining contact with the canal wall on the outstroke to minimise a debris blockage apically. The use of the file in a forwards and backwards motion, as if watch winding, with slight apical pressure. Watch winding and circumferential filing technique The files can be used within rotary systems or manually for a higher level of control. Many Nickel-titanium files are available. The super elasticity also means the risk of zipping and apical transportation is reduced. This allows an adequate taper of the root canal which takes less time to prepare than with stainless steel and less files needed. The superelasticity allows an increase in taper (between 4–8%) compared to stainless steel. This reduces the risk of deformation within the root canal as forces of compression and tension are absent. It also has the characteristic of 'shape memory' which allows it to return to its initial shape through heating after strain. Nickel-titanium is a superelastic alloy which allows it to undergo greater stresses compared to stainless steel therefore files have a reduced risk of file fracture.
C-type files Ĭ-files are stiffer than K-files, and are recommended for calcified canals and ones that are curved and narrow. The K-flex file differs for the fact it has a rhomboid shaped cross-section and has an increased flexibility compared to traditional K-files. The cutting edge of K type files is made up of twisted squares of stainless steel alloy. This information can help determine strategies or avoid complications before moving on to rotary instruments. This allows the dentist to feel changes in resistance or angulation, which can help determine curvature, calcification and/or changes in anatomy, in which two dimensional radiographs may not always identify. Hand files can provide tactile sensation when cleaning or shaping root canals. From left: Lentulo spiral, reamer, K-file and H-file.
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