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Selection of an appropriate nickel–titanium (NiTi) rotary system is important for minimally invasive endodontic treatment, which aims to preserve as much root canal dentin as possible. This study aimed to evaluate selected mechanical properties and the root canal shaping ability of TruNatomy (TRN), a NiTi rotary system designed for minimally invasive endodontic shaping, in comparison with existing instruments: HyFlex EDM (HEDM), ProTaper Next (PTN), and WaveOne Gold (WOG). Load values measured with a cantilever bending test were ranked as TRN < HEDM < WOG < PTN (p < 0.05). A dynamic cyclic fatigue test revealed that the number of cycles to fracture was ranked as HEDM > WOG > TRN > PTN (p < 0.05). Torque and vertical force generated during instrumentation of J-shaped artificial resin canals were measured using an automated instrumentation device connected to a torque and vertical force measuring system; TRN exhibited smaller torque and vertical force values in most comparisons with the other instruments. The canal centering ratio for TRN was smaller than or comparable to that for the other instruments except for WOG at the apex level. Under the present experimental conditions, TRN showed higher flexibility and lower torque and vertical force values than the other instruments.

Context: Cleaning and shaping of the canals damages the root dentin which becomes a gateway to dentinal cracks and thereby causes failure of the treatment. Aim: The aim of this study was to assess and compare dentinal crack formation caused by three different nickel-titanium (NiTi) rotary file systems in primary anterior teeth. Settings and Design: The present in vitro study is an experimental, comparative study. Materials and Methods: One hundred fifty extracted primary anterior teeth were included in this study. The teeth were randomly divided into five groups. Group 1: Pedoflex rotary file system, Group 2: Prime Pedo™ rotary file system, Group 3: Kedo-S2 rotary file system, Group 4: K-files, and Group 5: no instrumentation. Roots were sectioned and viewed under a stereomicroscope for the presence of any cracks. Statistical Analysis Used: The data were analyzed using the Chi-square test and Kruskal-Wallis test. Results: In the coronal, middle, and apical thirds, Group 2 showed a maximum number of crack formations in the middle third (57%), followed by Group 3 (43.3%) and Group 1 (36.7%). Groups 4 and 5 showed no crack formation in all the root sections. The middle third showed a maximum number of crack formations compared to the coronal and apical thirds. Conclusions: Rotary systems render various benefits with an acceptable success in comparison to conventional hand instrumentation. Within the limitation of this study, it was found that Pedoflex rotary file system was the best with the least number of crack formations.

Metal implants, especially Ni-Ti shape memory alloy (Ni-Ti SMA) implants, have increasingly become the first choice for fracture and massive bone defects after orthopedic bone tumor surgery. In this paper, the internal composition and shape memory properties of Ni-Ti shape memory alloy were studied. In addition, the effects of porous Ni-Ti SMA on osseointegration, and the effects of surface hydrophobicity and hydrophilicity on the osseointegration of Ni-Ti implants were also investigated. In addition, the effect of surface coating modification technology of Ni-Ti shape memory alloy on bone bonding was also studied. Several kinds of Ni-Ti alloy implants commonly used in orthopedic clinic and their advantages and disadvantages were introduced. The surface changes of Ni-Ti alloy implants promote bone fusion, enhance the adhesion of red blood cells and platelets, promote local tissue regeneration and fracture healing. In the field of orthopaedics, the use of Ni-Ti shape memory alloy implants significantly promoted clinical development. Due to the introduction of the coating, the osseointegration and biocompatibility of the implant surface have been enhanced, and the success rate of the implant has been greatly improved.

The aim of the present study is twofold: to assess ex vivo the role of different lubricants on real-time torque generated during intracanal instrumentation and to check whether two different kinds of torque parameters, operative torque (OT) and average peak torque (APT), could produce similar results. Forty extracted single-rooted teeth were selected for the present study and divided into four equal groups (n = 10): Group A, NaCl 0.2%; Group B, NaOCl 5%; Group C, ethylenediaminetetraacetate (EDTA), and Group D, EDTA and hydrogen peroxide. Afterwards, Edge Taper F2 (Edge Endo, Albuquerque, New Mexico) were rotated clockwise at 300 rpm with 3 Ncm maximum torque by an endodontic torque recording motor. In each sample, mean OT and mean APT were recorded and statistically analyzed with one-way ANOVA and a post hoc Bonferroni between groups (p < 0.05). EDTA (12.11 ± 4.45 Ncm) showed statistically significant (p < 0.05) lower values compared with the other tested irrigant for both parameters. Overall, the two different parameters were both able to differentiate between the influence of lubricants on torsional loads.

Protaper Universal (PTU), Protaper Gold (PTG) (Maillefer, Ballaigues, CH), EdgeTaper (ET), and EdgeTaper Platinum (ETP) (Albuquerque, NM, USA) were tested for both torsional and flexural resistance. The aim of the present study was to evaluate the influence of proprietary heat treatment on the metallurgical properties of the aforementioned instruments. Four groups of 30 different instruments (size 20.07) were tested, then divided into two subgroups of 15 instruments—one for the cyclic fatigue test in a curved canal (90°—2 mm radius) at 300 rpm and 2.5 Ncm. The time to fracture (TtF) and fragment length (FL) were recorded. The other subgroup was subjected to the torsional test (300 rpm, 5.5 Ncm). The torque to fracture and TtF were recorded. All the instruments underwent a SEM analysis. The heat-treated instruments showed a significantly higher fatigue resistance than the non-heat-treated instruments (p < 0.05). No significant differences were found in the torsional resistance between the ET and PTU, and the ETP and PTG. However, when comparing all the groups, the heat-treated instruments showed less torsional resistance. The improvement from heat treatment was mainly found in the cyclic fatigue resistance.

Metallic materials including stainless steel, cobalt-chromium alloys, titanium and its alloys, and nickel-titanium (NiTi) shape memory alloys have been used in biomedical applications since the 1940s due to their favorable mechanical properties. Classified as a smart material, NiTi alloy has gained noticeable popularity in biomedical fields such as orthopedic, dental, and cardiovascular applications as it retains reasonable corrosion resistance and biocompatibility along with unique shape memory properties. However, several studies have shown their limits in medical applications due to the risk of Ni ions release from the NiTi implant surface. In order to prevent Ni release, ceramic-based surface coatings such as hydroxyapatite, alumina, and titanium dioxide have been proposed applied by various methods such as electrophoretic deposition, sol-gel, biomimetic and dip coating. In this work, HA coatings on NiTi wire samples were obtained by using biomimetic and dip-coating methods. The biomimetic coating consisted of immersing the NiTi wire samples into simulated body fluid for 24 and 48 h periods, whereas dip coating was accomplished by placing the NiTi wire samples into the HA suspension and retracting the sample with a controlled speed. The effects of the two coating methods on coating quality, surface characteristics and corrosion behavior of NiTi wire samples were investigated. Dip coating method was shown to be a more favorable technique for the NiTi wire samples used throughout this study.

Orthodontic archwires, especially nickel-titanium (NiTi) ones, are a major source of nickel release. Despite their importance, no in vivo studies have assessed the ion release from conventional or new generations of NiTi archwires (copper-included and epoxy-coated). This double-blind parallel randomized clinical trial was done on 84 saliva specimens sampled at two time points from 42 orthodontic patients. The patients were randomly divided into three groups of NiTi, copper NiTi (NiTiCu), and epoxy NiTi archwires ( n  = 14 each). The effects of 2-month treatment, wire types, gender, and age on pretreatment, posttreatment, and time-dependent differences were analyzed statistically ( α  = 0.05). Salivary nickel concentrations were 10.4571 ± 0.77168 and 11.0779 ± 0.81232 μg/L, respectively, in the baseline and second month. This increase was significant ( P  = 0.0000, paired t test). The extents of nickel increase in different groups were 0.8279 ± 0.14 (NiTi), 0.6493 ± 0.10 (NiTiCu), and 0.385 ± 0.11 (epoxy-coated NiTi) μg/L ( P  = 0.0000, one-way analyses of variance (ANOVA)). Differences between each two archwire types were significant ( P  = 0.000, Tukey). Age and gender did not play a role. It can be concluded that NiTi archwires might increase nickel salivary levels. Epoxy-coated NiTi followed by copper NiTi archwires might release less nickel compared to conventional NiTi ones.

The biocompatibility of implantable nickel–titanium biomaterials relies on the quality of their surfaces. In this study, nickel–titanium surfaces are coated with phenolic thin films of tannic acid and pyrogallol with the purpose of studying their corrosion resistance in physiological environments. Three tests are performed: the open-circuit potential test, potentiodynamic polarisation and potentiostatic electrochemical impedance spectroscopy. Polarisation measurements are scrutinised in order to gain knowledge concerning the kinetics of the cathodic and anodic reactions, while the open-circuit potentials and impedance spectroscopy help to study the electrolyte–surficial interactions. It is found that coating nitinol with polyphenols results in the depletion of the native oxide layer and thus a decrease of corrosion resistance. Pyrogallic treated nitinol surfaces (with a corrosion rate of 0.119 mm/year) are half as electrochemically corrosion resistive as tannic acid-coated substrate. Therefore, it is proposed that tannic treated nitinol would be a better option if implanted on biomaterial surfaces.

This study explores the synergistic effect of Wire Arc Additive Manufactured (WAAM) NiTi shape memory alloys (SMAs) subjected to laser shock peening (LSP) on the surface morphology, microstructure, tensile properties, and fracture behavior, with a prime focus on enhancing material performance for advanced engineering applications. NiTi walls were fabricated using the WAAM technique and subjected to laser shock peening (LSP) with various intensities. The microstructural study of the as-manufactured (AM) NiTi alloy displayed a non-uniform distribution of phases, including retained austenite and martensite, which was refined with successive LSP treatments. The application of LSP treatment resulted in surface plastic deformation and enhanced carbon diffusion with Ni-enriched surface. Phase transition behavior was assessed using differential scanning calorimetry (DSC) analysis. For martensitic and austenitic transformations, the AM samples showed wide temperature ranges. Transformation temperatures gradually decreased with successive LSP treatments, suggesting that the austenitic phase had stabilized; this is mainly due to the microstructural refinement brought on by LSP, demonstrating how LSP can be used to customize phase transformation properties for improved functional performance. Microtensile testing demonstrated that LSP had a substantial positive impact on both the yield strength (YS) and ultimate tensile strength (UTS) of the NiTi alloy. The LSP-3 (10 GW/cm 2 ) treated sample exhibited a maximum UTS of 426.57 MPa and a toughness of 17.90 MJ/mm 3 . Post-SEM fractographic study of the AM NiTi samples displayed a brittle fracture mode, which was characterized by hard cleavage facets. The use of LSP treatment resulted in the development of a more uniform surface characterized by transgranular fracture properties and ductile tearing, which suggests an enhancement in toughness and strength. In addition, the application of LSP resulted in a considerable decrease in porosity in the samples. The samples treated with LSP-3 had the lowest porosity measuring at 4.10%. These findings highlight the potential of LSP as a transformational post-processing technique for improving the mechanical characteristics of WAAM-fabricated NiTi SMAs.

This simulated study of 30 severely curved L-shaped root canals aimed to compare preparation time, aberrations, width measurements, and fractured files of three nickel-titanium (Ni-Ti) files, namely, ProTaper, ProTaper Next (PTN), and WaveOne (WO). Thirty simulated L-curved root canals of resin blocks were randomly divided into three groups. The canals were prepared to a tip size of 25 using ProTaper, PTN, and WO rotary file systems. Pre- and post-operative views for each sample were captured by a professional camera at a standardized distance and position. Blue India ink was injected into the pre-operative canals, and red India ink was injected into the post-operative canals to give a clear superimposition image. Five points were assessed through the halfway of the canal to the orifice (area between the beginning of curvature and apical end point). Preparation time, aberrations, width measurements, and fractured files were recorded and analyzed. Mean preparation time was longest in ProTaper (4.89±0.68 minutes). PTN and WO were the fastest in preparing the canals (about 3 minutes). A statistically significant difference was found between WO and ProTaper & PTN and ProTaper (p=0.000), while the difference was non-significant (p > 0.05) between WO and PTN. Nine aberrations consisting of three zips, one ledge and one outer widening were related to ProTaper, while WO recorded a ledge and fractured file, but for PTN system, it verified an outer widening and ledge. Only one WO file fractured, with no deformation observed in the other instruments. No significance was recorded among the width measurements in the different levels. ProTaper next achieved faster cutting than the ProTaper and WO file systems. PTN maintained the best apical termination position and produced the least canal aberration, followed by WO and ProTaper.