![]() FEA results showed the stress locations and values during the insertion and rotation process, but the prediction of fatigue life required the presence of a fatigue failure criterion. Mechanical data extracted from the results of the second chapter were applied to user-defined material subroutines in FEA in a 2-step method. The fourth chapter used a finite-element version of the test method described in the third chapter, within which instruments comprised of the materials tested in the second chapter were evaluated. Two instruments with identical geometry but different metallurgical properties were tested, and both satisfied the strain limits proposed for the norm, and were therefore considered viable as a standardised test device for future studies. The third chapter investigated a proposed cyclic fatigue test rig for its suitability for the inclusion in the ISO 3630-1 norm. The values for the austenitic elastic moduli and transformation stress were also affected by the temperature of the fluid medium. The values for the martensitic elastic moduli were not significantly different among the four NiTi tested, however values for austenitic elastic moduli and transformation stress were significantly different between the untreated and heat-treated specimen groups. ![]() Samples were immersed in a temperature-controlled water bath. A purpose-built experimental setup was used for the tensile tests to allow for the variable of temperature to be explored, an aspect that was missing from prior work. In the second chapter of this thesis, different types of NiTi types in the form of small wire blanks were subjected to differential scanning calorimetry (DSC) and microtensile tests to establish their mechanical properties and limits. Despite greater complexity in both experimental and FEA studies of cyclic fatigue resistance of instruments, existing work lacks a standardised approach and a robust framework for predicting the cyclic fatigue life of rotary endodontic instruments. The use of this approach has been sparse, but has risen in frequency in the last decade. In the first chapter of the present work, a review of the current literature on FEA for studying the performance of NiTi instruments is presented. Among many applications, FEA has been used to test the effect of different boundary and load conditions on rotary NiTi endodontic instruments. Despite this, mechanical failure, often via cyclic fatigue, can lead to instrument fracture, and this in turn may result in adverse treatment outcomes.įinite element analysis (FEA) is a numerical method for conducting simulations of experimental designs. Modifications to the metallurgical types of these instruments have been introduced in successive iterations. Currently, these instruments are available to clinicians in a plethora of complex geometrical designs and specifications. ![]() Nickel-titanium (NiTi) rotary endodontic instruments are a critical component in cleaning and shaping of the root canal system in clinical dentistry. The objective of this literature review is to present and discuss the characteristics of the NiTi alloys used in the major instrumentation systems available in the market, as well as the influence of the metallurgical and mechanical properties of NiTi instruments and the movements that drive them, to enable more accurate and predictable planning of root canal preparation. An understanding of the mechanical properties of these new NiTi instruments and their effect on the clinical performance of root canal preparation is essential if dental practitioners are to select the instruments that provide optimal clinical outcomes, especially in curved or flattened canals. In addition, new movements have also been incorporated to offer greater safety and efficiency, optimizing the properties of the NiTi alloy, especially through eccentric rotary motion. In recent years, endodontic instruments have undergone a series of changes brought about by modifications in design, surface treatments, and thermal treatments. The introduction of automated instrumentation in endodontics represented a major advance in progress for this specialty, with improvements in the quality and predictability of root canal preparation and a significant reduction in procedural errors. ![]()
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