NiTi Systems Research Articles

Comparison of the Cleaning Effectiveness and Incidence of Dentinal Defects after Biomechanical Preparation Using Different Ni Ti Rotary Instruments in Root Canals

Purpose: This study was directed to evaluate the cleaning effectiveness& the dentinal defects incidence after preparation with different Ni-Ti rotary instruments in permanent molar root canals. Materials and Methods: A 60 human permanent lower first molars were used in this study. According to the Ni-Ti rotary system used in canal instrumentation, specimens were divided into 3 main groups (n=20) (One Shape, HyFlex EDM and XP-Endo Shaper). Each system was used as the suggested settings by manufacture. Each group was received Copious irrigation with 2.6% NaOCl was performed after the use of each file and finally with combination of 17% EDTA and 2.6% NaOCl. Then specimens were washed with distilled water. Each main group was divided into two subgroups (A &B) (n=10) according to evaluation methods: Subgroup A: The cleaning effectiveness (Scanning electron microscopic (SEM) evaluation). Subgroup B: The incidence of dentinal defects (Steriomicroscope evaluation). Results: Regarding to cleaning effectiveness, highest mean and standard deviation values were recorded for HF system while lowest mean value was recorded for XP system. Regarding to dentinal defects, the highest mean and standard deviation values were recorded for OS system, while the lowest mean value was recorded for XP system. Conclusions: The results of the present study showing that: XP-Endo Shaper file gives promising better results in cleaning ability with minimal incidence of dentinal defects found in root dentin.

The efficiency of canal cleaning with reciprocating movements instruments - SEM study

Introduction/Objective. The application of nickel?titanium (NiTi) instruments in cleaning and shaping of the root canal system is a standard and a precondition for the success of endodontic treatment. The objective of this study was to use scanning electron microscopy (SEM) analysis in order to examine the efficiency of cleaning the apical third of the root canal system using two different NiTi systems with reciprocating movements. Methods. The study included 20 single-rooted teeth (premolars) divided into two groups. In group 1, the canal preparation was realized with a single file UNICONE with reciprocating movements (MEDIN, Inc., Nove M?sto na Morav?, Czech Republic), and in group 2, with ? RECIPROC BLUE instrument with reciprocating movements (VDW GmbH, Munich, Germany). The same quantities of 2% NaOCl solution and 17% EDTA solution were used as irrigation solutions. The samples prepared for SEM analysis of the smear layer in the apical third were evaluated on a scale of 1?5 and at a magnification of 1,000?. Results. SEM analysis pointed to mostly clean canal walls in the apical segment in both tested groups. Slightly cleaner walls were observed after the application of the UNICONE file (78%) compared to the samples of the second group, where the instrumentation was realized by the RECIPROC BLUE file (76%), but without statistically significant differences. Conclusion. Single-file reciprocating systems do not remove the smear layer completely, but provide efficient cleaning of the apical region of the canal.

Cyclic fatigue resistance of three heat-treated nickel-titanium instruments at simulated body temperature

Introduction: The aim of this study was to evaluate the cyclic fatigue resistance of three heat-treated nickel–titanium (NiTi) systems at simulated body temperature. Materials and Methods: Twelve instruments of similar apical diameter (#25) from three engine-driven NiTi instruments; WaveOne Gold (WOG), Hyflex EDM (HEDM), and M Pro system were tested for cyclic fatigue resistance at 37°C in simulated root canals with 60° angle of curvature and 5 mm curvature radius. All instruments were operated until fracture occurred. Mean and standard deviation of the time to fracture and fragment length were calculated, and statistical significance was set at 5%. The morphological characteristics of the fractured instruments were observed through scanning electron microscopy, and their chemical composition was determined using energy dispersive X-ray analysis (EDXA). Results: HEDM showed the highest resistance to cyclic fatigue at 37°C followed by WOG and M Pro instruments with a statistically significant difference. Scanning electron micrographs confirmed a predominantly ductile mode of fracture for all instruments. EDXA showed that WOG was composed of Ni (45.1 wt%) and Ti (37.0 wt%), HEDM was composed of Ni (52.9 wt%) and Ti (42.4 wt%), and M Pro was composed of Ni (49.7 wt%) and Ti (40.4 wt%). Conclusions: M Pro instrument showed the least cyclic fatigue resistance at 37°C compared to HEDM and WOG.

Функциональная усталость сплавов с эффектом памяти формы систем Ni-Mn-Ga и Ni-Ti в условиях термоциклирования под постоянной нагрузкой

A comparative study of the functional properties and functional fatigue of Ni-Mn-Ga alloys in the initial cast state and Ni-Ti alloys in the initial hot-forged state without heat treatment was carried out. Measurements were carried out using experimental technique of three-point bending of samples in the form of plates of ~ 0.7 mm x 10 mm x 1.5 mm. It is shown that Ni2MnGa alloy in the cast state is preferably used for lightly loaded actuators (up to 100 MPa) and reversible deformations (up to 1.5%) in the temperature range from -85 C to -75 C; Ni-Ti system alloy in hot-forged state is recommended for highly loaded actuators (up to 500 MPa) , high reversible deformations (up to 8.5%) in the temperature range from -40 C to 40 C.

Cleaning ability of rotary NiTi systems with different kinematics

BackgroundThe aim of this study was to compare the cleaning ability of rotary NiTi systems with different kinematics: ProTaper Next (PTN) (continuous rotation motion), WaveOne Gold (WOG) (reciprocating motion), and Twisted File Adaptive (TFA) (adaptive motion).MethodologySixty mesiobuccal roots from extracted mandibular molars were divided into three groups (n = 20): PTN, prepared by ProTaper Next; WOG, prepared by WaveOne Gold system; and TFA, prepared by Twisted File Adaptive systems. Teeth were longitudinally split into two halves for evaluation by scanning electron microscope. Images were analysed for debris and smear layer scores using the scoring system described by Hülsmann et al. (J Endod 23:301–6, 1997).ResultsNo significant difference was found between the three groups in the coronal one third (P = 0.071). However, the TFA group recorded a significantly higher percentage of debris in the middle and apical thirds (P < 0.001 and P < 0.001, respectively)ConclusionsUnder the conditions of this study, adaptive motion produced more debris than the reciprocating and the continuous rotating motions.

Obtaining Functional Intermetallic Ni–Ti Coatings by Heterophase Transfer Combined with Laser Treatment

The results of the investigation of the intermetallic Ni–Ti system coating obtained by the complex method of cold gas dynamic spraying and laser treatment are presented. The dependence of the coating charge composition on the initial powder composition is shown. Its structure, porosity, and microhardness are studied, and also the results of X-ray phase analysis confirming the presence of the intermetallic phase are presented. The microhardness is increased by more than a factor of 5 to 632 HV, and the porosity is decreased by a factor of 25 to 0.2%. Investigation of the substrate–coating boundary shows the presence of mutual diffusion.

A Comparative Study to Assess the Post Operative Pain Intensity Following Non-Surgical Root Canal Treatment and Pulp Revascularization in Mature Necrotic teeth

Introduction: Traditionally necrotic permanent teeth are managed through the conventional procedures of root canal treatment which is known to weaken the remaining tooth structure. Regenerative Endodontic Procedures so have emerged as an alternative to the conventional techniqueAim of the study: The aim of the present study was to compare the post-operative pain intensity following non-surgical root canal treatment and revascularization procedures in mature necrotic teeth.Materials and methods: Twenty-four adult participants with 30 necrotic mature maxillary anterior teeth were randomly divided into two groups according to the treatment modality; control group: non-surgical root canal treatment; Intervention group: Blood clot revascularization technique. At the first visit in the two groups, all patients recorded their pain level preoperatively using a numerical rating scale (NRS). Mechanical preparation was performed with the ProTaper Universal Ni Ti system up to #F4 file. Double antibiotic paste (DAP) was prepared and injected and the cavity was temporarily sealed. At the second visit, three weeks later, the patients were assigned according to the randomization. The degree of spontaneous postoperative pain was measured using NRS after 6, 12, 24, and 48 hours.Results: Independent t -test between both groups; showed a highly significance difference, p value 0.05.

Efficacy of R-Endo and E3-ReRoot Retreatment Rotary NiTi Systems in Intracanal Filling Material Removal

Aim: To compare the effectiveness of R-Endo and E3-ReRoot retreatment rotary files in filling material removal and operating time.Materials and Methods: Twenty extracted distobuccal roots of maxillary first molars were decoronated to a standard length of 12 mm. Root canal preparations were done using Fanta Blue (Fanta; ShangHai, China) till 0.04/25. Matching gutta percha cones of 0.04/25 were used with Adseal resin sealer (Meta Biomed, Chungcheongbuk-do, Republic of Korea) in warm vertical compaction technique. Teeth were left in an incubator at 37 °C and 100% humidity for 30 days. Cone beam computed tomographic images of all roots were obtained to confirm three-dimensional filling of the root canal space. Roots were divided into two groups according to the file used in retreatment; group A using R-Endo (Micro-Mega, Besancon, France) and group B using E3-ReRoot (IMD; ShangHai, China). Time required to remove the filling material was recorded in seconds. Teeth were then split into two halves using hammer and chisel and remaining filling material was calculated using stereomicroscope at 4X original magnification. Statistical analysis was performed using One-Way ANOVA and significance level was set at 0.05.Results: E3-ReRoot was shown to be significantly more effective than R-Endo in intracanal filling removal. No significant difference was shown between both systems in the time needed to reach the working length. Conclusion: E3-ReRoot was more effective in intracanal filling removal although both systems failed to totally remove gutta percha and sealer remnants from the root canals.

ALL ROADS LEAD TO DOPAMINE: EXPLORING THE GENETIC LINK BETWEEN ADHD, OBESITY MEASURES AND BRAIN VOLUMES

For the great potential Fe-Mn-Si shape memory alloy (Fe-SMA), which is less expensive compared with the Ni-Ti system, tension-compression asymmetry in stress-strain curve is reported in the past. It is considered that the difference in thermomechanical and stress-induced martensitic transformation behavior may also be observed under different loading modes in Fe-SMA. In this paper, an experimental investigation under compression is conducted to make clear the rate dependency of thermomechanical and phase transformation behavior in Fe-SMA at the previous study focusing on the behavior under tension. During both quasi-static and impact compression, the amount of stress-induced ε-martensite can be indirectly evaluated by using a real-time measurement method of an electrical resistance. Furthermore, temperature change which becomes an important aspect of the study on the phase transition is also captured. In addition, after compressive test and heating, it is attempted to investigate the rate dependency of volume fraction of stress-induced ε-martensite and shape recovery strain. Finally, the microstructural observation of the samples taken from the specimen is carried out.

LIQUIDUS SURFACE AND MELTING DIAGRAM OF THE TERNARY Ni–Ti–Zr SYSTEM IN RICH IN NICKEL AREA OF CONTENTS

Multicomponent alloys based on Ni–Ti system known as high-temperature corrosion-resistant materials that have an attractive combination of mechanical, chemical and physical properties and are used as structural materials and functional diversification purposes. The ternary alloys of the Ni–Ti–Zr system attract attention, in particular, due to their ability to crystallize in an amorphous state at relatively low cooling rates, that is, they have the ability to form so-called bulk amorphous alloys. Literature data concern phase equilibria in the ternary system are rather limited. The system was studied in temperature interval from 700 °С to the liquidus surface in the concentration range from 0 to 50% (at.) Ni by Eremenko with co-authors (1988-1992). There is the only work in the solid / liquid equilibria region with a nickel content of more than 50 % (at.) – Liu X.J. et al (2015) – isothermal sections at 1000 and 1200 °С, that does not give an idea about crystallization processes. Besides in our previous work the solidus surface projection was constructed. In present work we present the results about the phase equilibria in the melting / crystallization region in the concentration range from 75 to 100 % (at.) Ni. The arc-melting alloys were studied by scanning electron microscopy with electron probe microanalysis (SEM / EPMA) and differential thermal analysis (DTA). Based on the results of the experimental study the liquidus surface projection and the melting diagram of the ternary one Ni–Ti–Zr system in the region Ni–Ni3Ti–Ni7Zr2 are constructed. The liquidus surface consists of four fields of primary crystallization – solid solutions of ⟨Ni⟩, ⟨Ni3Ti⟩, ⟨Ni5Zr⟩ and ⟨Ni7Zr2⟩. The liquidus temperature decreases from the bounding binary systems to the ternary one to a minimum at 1182 °С at the point Ni84.5Ti7.9Zr7.6 of the ternary eutectics composition LЕ1 ↔ ⟨Ni⟩ + ⟨Ni3Ti⟩ + ⟨Ni5Zr⟩. The invariant point coordinates on liquidus surface were established: LU1 + ⟨Ni7Zr2⟩ ↔ ⟨Ni5Zr⟩ + ⟨Ni3Ti2⟩ – Ni83.0Ti8.5Zr8.5, 1190 °С; lе3 ↔ Ni + Ni5Zr – Ni87.4Ti4.5Zr8.1, 1187 °С; lе2 ↔ Ni3Ti + Ni7Zr2 – Ni76.3Ti13.2Zr10.5, 1288 °С.

Follow-up structural evolution of Ni/Ti reactive nano and microlayers during diffusion bonding of NiTi to Ti6Al4V in a synchrotron beamline

Reaction-Assisted Diffusion Bonding (RADB) of NiTi to Ti6Al4V using either magnetron sputtered Ni/Ti nanomultilayers or Ni/Ti commercial microfoils as filler material was studied. The joining process takes advantage of the exothermal reactive character of the Ni-Ti system to provide extra energy during the bonding process. Therefore, sound joints could be achieved at lower thermal conditions. The oven with load capabilities at the High Energy Materials Science beamline (P07) of the Deutsch Synchrotron (DESY) is ideal to follow the structural evolution of the materials involved in the bonding process. Prior to RABD, Ni/Ti multilayers with a 2.5 μm total thickness and with 12 or 25 nm of modulation period were deposited onto the materials being joined. In alternative, up to 20 alternated thin μ-foils were placed in between the base materials. The materials were heated by induction to the selected temperature during 30 min and quenched to room temperature by blowing helium. During the thermal cycle a 10 MPa pressure was applied. Using thin μ-foils, 650 °C was required to promote joining, while using multilayer coated materials sound joints were obtained at 600 °C. Such low temperatures are attractive from the application/economic point of view, and are crucial to reduce the formation of undesired intermetallic phases, such as NiTi2. The nanoindentation experiments of the joints processed using Ni/Ti nanomultilayers confirm that the presence of the NiTi2 phase is more pronounced at 650 °C than when the joints are processed at 600 °C.

Formation of Intermetallics Layers in Ni-Ti System Prepared by Direct Energy Deposition

The Ni-Ti alloys with approximately equiatomic chemical composition are one of the most important materials from the shape memory alloys. Excellent properties such as shape memory effect and superelasticity are based on the phase transformation between austenite and martensite structure of the NiTi phase. In the past the investigation of the preparation methods was focused on melting metallurgy - vacuum induction melting and arc re-melting and powder metallurgy routes like self-propagating high-temperature synthesis, hot isostatic pressing and spark plasma sintering. In the last several years importance of the additive manufacturing has increased significantly. This paper deals with formation of the Ni-Ti intermetallic phases between the nickel and titanium layers deposited on each other by direct energy deposition energy method. The varied mixture of the Ti 2Ni, NiTi and Ni3Ti phases was formed in agreement with the binary Ni-Ti phase diagram. Some problems like cracking and nickel loss have to be solved by preheating of platform or adjustment of laser parameters.

Colossal Elastocaloric Effect in Ferroelastic Ni-Mn-Ti Alloys.

Energy-efficient and environment-friendly elastocaloric refrigeration, which is a promising replacement of the conventional vapor-compression refrigeration, requires extraordinary elastocaloric properties. Hitherto the largest elastocaloric effect is obtained in small-size films and wires of the prototype NiTi system. Here, we report a colossal elastocaloric effect, well exceeding that of NiTi alloys, in a class of bulk polycrystalline NiMn-based materials designed with the criterion of simultaneously having large volume change across phase transition and good mechanical properties. The reversible adiabatic temperature change reaches a strikingly high value of 31.5K and the isothermal entropy change is as large as 45 J kg^{-1} K^{-1}. The achievement of such a colossal elastocaloric effect in bulk polycrystalline materials should push a significant step forward towards large-scale elastocaloric refrigeration applications. Moreover, our design strategy may inspire the discovery of giant caloric effects in a broad range of ferroelastic materials.

Efficacy of Two Different Nickel-Titanium Rotary Systems in Retreatment Procedure With or Without Laser-Activated Irrigation: An In Vitro Study.

Objective: The aim of this study was to compare the efficacy of HyFlex EDM (Coltene/Whaledent, Altstätten, Switzerland) and ProTaper Universal Retreatment Nickel-Titanium (NiTi) Systems [The ProTaper Universal Retreatment (PTR), Dentsply Maillefer, Ballaigues, Switzerland] in the removal of the root canal filling materials with or without laser activated irrigation. Materials and methods: The root canals of 60 human mandibular premolars were instrumented with K files up to size 35 at a working length; the step-back procedure was performed in 1 mm increments up to size 50. Next, the teeth were obturated using the lateral compaction technique with gutta-percha and resin-based sealer, and they were randomly divided into two groups (n = 30) according to the retreatment systems: PTR and HyFlex EDM NiTi rotary files. Then, each group was divided into two subgroups (n = 15), laser [photon-induced photo-acoustic streaming (PIPS); Fotona, Ljubljana, Slovenia] activated irrigation and conventional needle irrigation group. Following these procedures, the specimens were evaluated using micro-computed tomography. Results: There was no significant difference between the instrumentation systems regarding the cleaning efficacy (χ2 = 0.754; p = 0.86). Additionally, PIPS method did not have a significant effect on the removal of the filling material compared to conventional needle irrigation. Conclusions: Both instrumentation systems were effective in removing the filling material, but neither was able to remove the filling material completely. PIPS method did not show a significant additional effect regarding the removal of filling material.

On the versatility and distinctiveness in the use of microwave energy for the ignition of low exothermic Ni–Ti intermetallics combustion synthesis

Microwave energy has been employed in the present work in order to reach ignition of the combustion synthesis in the binary Ni–Ti system without the need of any separate additional pre-heating step. Indeed, the latter is known to be necessary with more conventional ignition strategies, due to the low exothermic character of the reaction between elemental Ni and Ti powders. On the opposite, the unique microwaves heating mechanism allows directly transferring electromagnetic energy in the reactive specimen that absorbs and transforms it into the heat necessary to reach ignition of the exothermic reaction. According to the electromagnetic field distribution inside the microwave single mode applicator employed, it was possible to realize both Thermal Explosion (TE) and Self-propagating High-temperature Synthesis (SHS) ways of combustion.Moreover, the use of a single mode applicator also allowed separately investigating the effect of electric and magnetic fields strengths, at the 2450 MHz microwave frequency, on the combustion characteristics. This significantly affected the microstructure as well as the phase evolution in the synthesized products.

An experimental investigation on rate dependency of thermomechanical and Stress-induced martensitic transformation behavior in Fe-28Mn-6Si-5Cr shape memory alloy under compression

For the great potential Fe-Mn-Si shape memory alloy (Fe-SMA), which is less expensive compared with the Ni-Ti system, tension-compression asymmetry in stress-strain curve is reported in the past. It is considered that the difference in thermomechanical and stress-induced martensitic transformation behavior may also be observed under different loading modes in Fe-SMA. In this paper, an experimental investigation under compression is conducted to make clear the rate dependency of thermomechanical and phase transformation behavior in Fe-SMA at the previous study focusing on the behavior under tension. During both quasi-static and impact compression, the amount of stress-induced ε-martensite can be indirectly evaluated by using a real-time measurement method of an electrical resistance. Furthermore, temperature change which becomes an important aspect of the study on the phase transition is also captured. In addition, after compressive test and heating, it is attempted to investigate the rate dependency of volume fraction of stress-induced ε-martensite and shape recovery strain. Finally, the microstructural observation of the samples taken from the specimen is carried out.

Symmetry and pathway analyses of the twinning modes in Ni–Ti shape memory alloys

The complex interplay of multiple deformation modes in Ni–Ti systems play a critical role in determining the mechanical properties of the shape memory alloys, e.g., superelasticity, shape memory effect and functional fatigue resistance. In particular, several different twinning modes have been observed in experiments, which include both transformation twins (generated by a phase transformation between two phases) and mechanical twins (generated in a single phase). In spite of well-established theories to treat transformation twins and mechanical twins independently, a general framework capturing the intrinsic coupling between them is still unavailable. Here we systematically analyze all the twinning modes in Ni–Ti alloys, by employing a phase transition graph approach. We show that transformation twins and mechanical twins are intrinsically coupled in symmetry-breaking processes, which results in multiple interconnected deformation pathways. By investigating those deformation pathways, we demonstrate additional characteristic twinning modes arising from the coupling, which includes both symmetric and asymmetric twins. Our work provides a theoretical foundation to investigate the coupling between transformation twins and mechanical twins from a symmetry point of view.

Incidence of microcracks after preparation of straight and curved root canals with three different NiTi instrumentation techniques assessed by micro-CT.

This study evaluated the effect of three different NiTi instrumentation techniques on the incidence of microcracks after the preparation of straight and curved root canals using micro-CT. Roots from mandibular premolars and maxillary molars (n=66) with the same mean canal curvatures were assigned to three groups of straight and three groups of curved roots (n=11). After preoperative micro-CT scans, root canals were prepared with Reciproc, OneShape and ProTaper Next to size 25. Specimens were scanned again, and pre- and post-operative cross-sectional images (n=75263) were screened to identify the presence of dentinal microcracks. Overall, microcracks were detected in 2.97% (n=2236) of the cross-sectional images. No new dentinal microcracks were observed after root canal instrumentation of straight and curved canals with the tested NiTi systems. Instrumentation with Reciproc, OneShape and ProTaper Next did not induce the formation of dentinal microcracks irrespective of canal curvature.

Evaluation of XP-endo Shaper, Reciproc Blue, and ProTaper Universal NiTi Systems on Dentinal Microcrack Formation Using Micro–Computed Tomography

IntroductionThe purpose of the present study was to evaluate the frequency of dentinal microcracks observed after root canal preparation with XP-endo Shaper (XP), Reciproc Blue (RB), and ProTaper Universal (PTU) instruments using micro-computed tomographic (μCT) analysis. MethodsThirty extracted mandibular first and second molars with mesial roots having 2 separate canals with an angle between 10°and 20° were randomly assigned to 3 experimental groups (n = 10) according to the different nickel-titanium systems used for root canal preparation: XP, RB, and PTU. The specimens were scanned using μCT imaging before and after root canal preparation. Then, preoperative and postoperative cross-sectional images of the teeth were evaluated to identify the presence of dentinal defects. For each group, the number of microcracks was determined as a percentage rate. The McNemar test was used to determine significant differences before and after instrumentation. The level of significance was set at P ≤ .05. ResultsNo new dentinal microcracks were observed in the XP and RB groups. The PTU system significantly increased the percentage rate of microcracks compared with preoperative specimens (P < .05). ConclusionsRoot canal preparations with XP and RB systems might not induce the formation of new dentinal microcracks on the mesial roots of mandibular molars. Further assessments are suggested for the examination of the morphology of microcracks after the use of these instruments.

Obtaining the functional intermetallic Ni–Ti coatings by heterophase transfer combined with laser treatment

The results of the investigation of the intermetallic Ni–Ti system coating obtained by complex method of cold gasodynamic spraying and laser treatment are presented. The dependence of the coating charge composition on the initial powder composition is shown. Its structure, porosity, and microhardness are studied, and also the results of X-ray phase analysis confirming the presence of intermetallic phase are presented. The microhardness increased more than 5 times to 632 HV, and porosity decreased 25 times up to 0.2%. Investigation of the substrate-coating boundary showed the presence of mutual diffusion.