Investigation of the effects of root canal preparation and sterilization procedures on physical properties of traditional and memory control nickel titanium files

Nickel-titanium rotary systems are widely used to shape root canals, as they are more advantageous than conventional steel files. However, torsional and cyclic stresses also cause fractures in these instruments. Therefore, in order to increase the physical resistance of Ni-Ti instruments, a new generation of instruments produced by various heat treatments were introduced. One of them is controlled memory nickel titanium instruments. Ni-Ti instruments have been used many times in the clinic for economic reasons. These torsional and cyclic stresses, sterilization procedures and irrigation solutions lead to physical changes. As a result, instruments fractures occurs. The aim of study is investigate the physical changes caused by multiple uses on conventional and memory controlled Ni-Ti files. Hyflex CM (Coltene-whaledent, Altstatten, Switzerland) and Revo-S (Micromega, Besancon, France) files were used to shape canals on extracted teeth six times in total, as in clinical conditions and the physical changes occurring in the 1st, 3rd and 6th usage were examined by scanning electron microscope. According to the findings of our study, the amount of deformation seen in the instruments increased as the number of uses increased. Controlled-memory nickel-titanium rotary instruments were superior to conventional nickel-titanium rotary instruments in terms of deformation and microcrack formation at the end of the instruments. When the surface debris was examined, no organic debris was found in both groups.