Abstract
Introduction: The objective of this study was to measure the number of cycles to fracture of four continuous or reciprocating rotary nickel-titanium instruments in different materials. Methods: A total of 40 nickel-titanium instruments were used for the present study. Instruments were divided into four groups (n=10): group 1, Revo-S SU; group 2, ProTaper Next X2; group 3, Reciproc R25; group 4, WaveOne Gold Primary. An artificial stainless-steel was used to test the cyclic fatigue of the instruments. The instruments were introduced into the stainless-steel canal, one at a time, until they reached the other end, then they were rotated inside the canal without in-out motion. The time from the beginning of instrument rotation until the occurrence of breakage was recorded. The number of rotated cycles to fracture of the instrument were calculated based on the revolutions per minute (rpm) of each instrument and the recorded rotated time. The mean number of cycles to fracture and standard deviations were calculated and statistically analysed. Results: The number of cycles to fracture of the Revo-S SU was the lowest, and that of the WaveOne Gold Primary was highest. Scanning electronic microscope images of fracture surfaces revealed the characteristics of fatigue. Conclusions: The number of cycles to fracture of the reciprocating WaveOne Gold Primary system was the highest amongst the tested instruments.
Highlights
The objective of this study was to measure the number of cycles to fracture of four continuous or reciprocating rotary nickel-titanium instruments in different materials
Utilisation of nickel-titanium (NiTi) in rotary instruments was a revolution in root canal treatment and has become the standard for endodontic instrumentation.[1]
The centring ability of these instrument systems in curved root canals was superior to that of manual instruments and the preparation time for nickel-titanium instruments was significantly less than manual instruments.[2,3]
Summary
The objective of this study was to measure the number of cycles to fracture of four continuous or reciprocating rotary nickel-titanium instruments in different materials. To obtain successful results for endodontic treatment, clinicians must maintain the original anatomic configurations of the root canal systems without causing any mistakes.[1] Utilisation of nickel-titanium (NiTi) in rotary instruments was a revolution in root canal treatment and has become the standard for endodontic instrumentation.[1] The centring ability of these instrument systems in curved root canals was superior to that of manual instruments and the preparation time for nickel-titanium instruments was significantly less than manual instruments.[2,3] Two of the best characteristics of these nickel-titanium instruments are their high flexibility and shape-memory ability They have these good characteristics, these instruments seem to fracture in clinical application.[4] There were two main causes of endodontic instrument breakage, cyclic fatigue and torsional stress many other factors could affect this situation.[5] In fatigue failure, the fatigue of the material leads to instrument fracture. To overcome the drawback of nickel-titanium instruments, the manufacturers continuously improve the rotary instrument in terms of design, materials, modes of rotation and techniques to minimise the number of fractured instruments
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