Invitro evaluation of morphological changes of hyflex and protaper rotary systems in moderate to severe curved canals

NiTi has been extensively used for biomechanical preparation so far but the problem with this is unexpected file fracture. Recently thermal treatment has come up to improve mechanical properties of the alloy. Controlled memory wire (CM) of HyFlex is one of the thermally treated alloys. Till now no studies were reported in evaluating the morphological changes of these files. Hence a study was conducted to evaluate the morphological changes of HyFlex and ProTaper after clinical use and to observe the rewinding of the flutes after the autoclaving in HyFlex group under stereomicroscope at 40X magnification.

Hundred freshly extracted mandibular molars having moderate to severe curved canals were divided into two groups of 50 each. They were accessed and biomechanical preparation was done in mesiobuccal canals according to the manufacturer's instructions.

Group1: instrumented with HyFlex Group2: instrumented with ProTaper After each use the files were examined under stereomicroscope at 40 X magnification to observe unwinding. Scoring was given according to scoring criteria Score1: No unwinding, reverse winding Score 2: Unwinding or reverse winding and shortening of one spiral Score 3: Unwinding or reverse winding shortening of two spirals Score4: Unwinding or reverse winding and shortening of more than two spirals along the shaft examined.

Spiral distortion was not observed in ProTaper group till 11^th use while HyFlex group showed distortion at 3^rd use, there is no statistical significant difference between the groups till 3^rd use. (p>0.05).

Based on the results of the study it could be concluded that HyFlex files showed visible verification and are easily distorted when compared to ProTaper group