EVALUATION OF THE DEFECTS IN RECIPROCATING AND ROTATING NICKEL-TITANIUM FILES USED AS A SINGLE FILE TO PREPARE MOLAR TEETH

Aim: To evaluate the defects in five nickel-titanium instruments activated by reciprocating and rotating motions and used as a single file in molar teeth.
Materials and methods: Twenty files size 25 from five brands [WaveOne (WO); Reciproc (RC); OneShape (OS); ProTaper Next (PTN); and ProTaper Universal (PTU)] were tested as a single file to prepare mandibular molars teeth. Thereafter, the five brands were redistributed into two tested groups, rotating and reciprocating groups. The time required for instrumentation was recorded. New and used instruments were examined under a scanning electron microscope for defects, deformations and fractures. One-way ANOVA and Kruskal Wallis were used for data analysis.
Results: The RC and PTN were significantly faster than WO and OS (P<0.05), while PTU required significantly the longest time (P<0.05). The fracture incidence was zero % in the PTN and OS, and 5% in the WO and RC, while it was (10 %) in the PTU. The fractographic analysis revealed cyclic failure of PTU and WO and torsional failure in RC. OS had (15%) percentage of deformation, WO (5%), while it was zero% in the PTN, RC and PTU. Reciprocating motion was significantly faster than rotating motion (P<0.05) without significant difference in deformation incidence (P>0.05).
Conclusions: The ProTaper Next, Reciproc and WaveOne files, were less vulnerable to fracture and deformation than ProTaper Universal and OneShape files when used as a single file to prepare molar teeth. The ProTaper Next was faster and more resistant to failure than other groups. In addition, files used with the reciprocating motion were faster to finish molar teeth than rotating motion without a significant effect on the defect incidence.