Topographic Changes Of Two different Ni Ti File Systems After Multiple Uses

Aim: To study the topographic changes of protaper Next and Two Shape NiTi file systems after
three uses.
Materials and Methods: Four sets of Protaper Next and four sets of Two Shape files were
used to prepare MB canals of mandibular first molars. Twenty four mandibular first molars with
nearly similar lengths (20 to 22 mm) and the mesiobuccal canals with curvature ranged from 20o -
40o were used. All teeth were subjected to access cavity, MB canal localization, WL determination
and the teeth were randomly assigned to two groups, twelve for each according to the type of NiTi
rotary files used. Group I, twelve MB canals were prepared by using the four sets of Protaper Next
NiTi rotary files. Group II, twelve MB canals were prepared by using the four sets of Two Shape
NiTi rotary files. Every set prepare three canals. All sets of Protaper Next including X1 & X2 and
Two Shape including TS1 & TS2 were scanned under SEM before and after canal preparation in
the same position at three parts: apical part, middle part and the critical point (3-5 mm from the file
tip) and photographed. No visible defects, pitting, corrosion, fretting, micro cracks, fractures, metal
strips, spiral distortion, blunt cutting edges, disruption of cutting edges or fatigue cracks were the
criteria of surface deformations of files. All deformations were tabulated and compared before and
after root canal preparation.
Results: PTN sets: one X1 showed disruption of cutting edges before and after use, one X1
showed disruption of cutting edges after use, two X1 and four X2 files showed no visible defects.
TS sets: one TS1 showed disruption of cutting edges before and after use, three TS1 showed no
visible defects. One TS2 showed pitting before and after use, one TS2 showed corrosion after use,
one TS2 showed disruption of cutting edges and micro cracks after use and one TS2 showed no
visible defects.
Conclusion: Based on the results of this study, it is safe to instrument up to three curved canals
by PTN or TS rotary NiTi files without file fracture.