A dozen ways to prevent nickel-titanium rotary instrument fracture

Instrument Separation Analysis of Multi-used ProTaper Universal Rotary System during Root Canal Therapy

“…Thus, the increased severity of the angle and curve radius, around which the instrument rotates, will definitely shorten the instrument lifespan. ProTaper Universal instruments are designed with deep cutting flutes, progressive tapers, and rapidly changing cross-sectional diameters along the shafts, which usually develop a high level of torque and make them more prone to metal fatigue (35). As the file moves axially in the canal, different parts of the file are exposed to the flexure and cyclic fatigue (20).…”

Comparison of cyclic fatigue and torsional resistance in reciprocating single-file systems and continuous rotary instrumentation systems

“…The instrument tip fractures when torque exceeds the elastic limit of the metal (5). When the instrument is used for instrumentation in curved canals, compression force and tensile stress are alternately generated on each part of the instrument (6). Continuous repetition of these forces can cause instrument fracture (7).…”

Evaluation of Forces Generated on Three Different Rotary File Systems in Apical Third of Root Canal using Finite Element Analysis

“…A number of recommendations for preventing instrument fracture in the clinical situation, which are based on clinical observations and findings in laboratory investigations, have been proposed [25]. One should realize that there is no any instrument system that can be suitable for all clinical situations, and it is important to understand how the structural characteristics could influence the magnitude of stress on the instrument to prevent its fracture in use.…”