Search results for "Cyclic stress"
showing 10 items of 13 documents
An in vitro cyclic fatigue resistance comparison of conventional and new generation nickel-titanium rotary files
2018
Background New designs and processing of Niquel-Titanium (NiTi) have been introduced to increase resistance to cyclic fatigue. The purpose of this study was to compare the cyclic fatigue resistance of 3 NiTi rotary instruments, ProTaper Next (PTN; Dentsply Maillefer, Ballaigues, Switzerland), Profile Vortex Blue (PVB; Dentsply Tulsa Dental, Tulsa, OK, USA) and ProTaper Universal (PTU; Dentsply Maillefer, Ballaigues, Switzerland). Material and Methods A cyclic fatigue test was conducted operating instruments from ProTaper Next X2, Profile Vortex Blue 25.06 and ProTaper F2. A total of 234 instruments were rotated in 2 simulated stainless steel curved canals with different angles of curvature …
The Effect of Taper and Apical Diameter on the Cyclic Fatigue Resistance of Rotary Endodontic Files Using an Experimental Electronic Device
2021
The aim of this study was to analyze the effect of the taper and apical diameter of nickel&ndash
Variational methods for the steady state response of elastic–plastic solids subjected to cyclic loads
2003
Abstract Solids (or structures) of elastic–plastic internal variable material models and subjected to cyclic loads are considered. A minimum net resistant power theorem, direct consequence of the classical maximum intrinsic dissipation theorem of plasticity theory, is envisioned which describes the material behavior by determining the plastic flow mechanism (if any) corresponding to a given stress/hardening state. A maximum principle is provided which characterizes the optimal initial stress/hardening state of a cyclically loaded structure as the one such that the plastic strain and kinematic internal variable increments produced over a cycle are kinematically admissible. A steady cycle min…
Statistical Properties of Generalized Strain Criterion for Multiaxial Random Fatigue
1989
ABSTRACT Statistical properties of generalized criterion of the maximum shear and normal strains on the fracture plane have been presented, Functions of probability distribution and spectral density of the equivalent strain have been analysed on the assumption that a random tensor of strain state is a six-dimensional stationary and ergodic Gaussian process. The expected value and variance of the equivalent strain have been determined as well. From spectral analysis a new limitation has been derived for extension of some multiaxial cyclic fatigue criteria to random loadings. It is connected with the fact that in some cases the frequency band of the equivalent strain is greater than that for …
A comparative study of mechanical resistance of two reciprocating files
2019
Background To evaluate the cyclic fatigue resistance of two different Nickel-Titanium instruments, Reziflow (Komet, Brasseler GmbH & Co., Lemgo, Germany) and WaveOne Gold (Dentsply Maillefer, Ballaigues, Switzerland). Material and Methods Two groups of 20 different NiTi endodontic instruments of identical tip size of 0.25 mm were tested; Reziflow and Wave-One Gold primary. Cyclic fatigue testing was performed in a stainless steel simulated root canal manufactured by reproducing the instrument’s size and taper. A simulated root canal with a 90 degrees angle of curvature and 5 mm radius of curvature was constructed for the instruments tested. The centre of the curvature was 5 mm from the tip …
Influence of the type of reciprocating motion on the cyclic fatigue resistance of reciprocating files in a dynamic model
2021
Abstract Background The aim of this study was to compare the influence of two novel reciprocating movements on the cyclic fatigue resistance of endodontic reciprocating files. Methods 30 Procodile® (Komet Medical, Lemgo, Germany) files were selected in this study and distributed according to the following study groups depending on the movements to be performed: ReFlex Dynamic (n = 10), ReFlex Smart (n = 10) and Reciproc (n = 10) reciprocating movement. These files were fixed to a specific dynamic cyclic fatigue device designed and manufactured by 3D impression to simulate the pecking motion performed by the operator. The time to failure and the number of cycles of in-and-out of the endodont…
Influence of the Pecking Motion Frequency on the Cyclic Fatigue Resistance of Endodontic Rotary Files
2019
This article belongs to the Special Issue Innovations in Endodontic Dentistry.
A Comparative Study of Cyclic Fatigue of 10 Different Types of Endodontic Instruments: an in Vitro Study
2019
Objective This study was designed to test the null hypothesis that there were no significant differences between size 25 files F360, F6 SkyTaper, Hyflex EDM, iRace, Neoniti, One Shape Protaper Next, Reciproc, Revo-S and Wave One Gold in terms of resistance to cyclic fatigue and length of broken fragments. Material and methods 300 new size 25 files of the systems studied were selected (n=30). The instruments were mechanized with a X-Smart Plus endo motor at the speed and torque recommended by the manufacturer, holding the instruments steady with a clamping mechanism, with passive adjustment and without pressure in a stainless-steel block. The time was calculated in seconds until fracture. Th…
Evaluation of Cyclic Fatigue of Hyflex EDM, Twisted Files, and ProTaper Gold Manufactured with Different Processes: An In Vitro Study.
2021
Introduction. The main aims of root canal instrumentation are to provide an environment that will lead to healing and to provide a root canal shape that is comfortable to clean and seal. When working with rotary endodontic instruments, the most significant concerns are that the instrument might fracture in the root canal, thus affecting the treatment outcome. Hence, it is of immense importance to know which file systems have more cyclic fatigue resistance. Methodology. This study evaluated the effect of the curved segment length of the artificial canal (the arch), and the number of cycles necessary in fracture of Hyflex EDM, Twisted files, and ProTaper Gold were recorded. Sixty NiTi rotary …
Fracture and deformation of ProTaper Next instruments after clinical use
2018
Background The aim of this study was to evaluate the fracture and defects observed in ProTaper Next files discarded after a normal clinical use. Material and Methods 571 ProTaper Next rotary instruments were collected after clinical use from the clinic of endodontics over 12 months. The length of the files was measured using a digital caliper to determine any fracture, later all the files were evaluated under a stereomicroscope to observe defects such as unwinding, curving or fracture. The data obtained were analyzed using a chi-square and z test. Results 13.83% of the discarded files showed defects, the most frequent defect was fracture (7.53%). The highest rate of fracture was observed in…