Micro-drilling on shape memory alloys-A review.

Technology like micro-hole drilling has progressed because of the machining industry's demand for high-precision micro components. Although micro drilling can be duplicated in theory, many challenges must be overcome before this becomes a reality. Micro-drilling with a thermal-mechanical interaction in the alloy is simulated in Abaqus. It looks at twist-bit modeling, material constitutive modeling, chip separation criteria, and element division. Focusing on work and tool electrode materials, hole specifications, micro hole types (through or blind holes), process parameters, performance measurements, and significant discoveries, this study presents a complete survey of the literature on spark methods for drilling microscopic holes. With an emphasis on spark erosion machining, drilling, and its modifications, this study seeks to aid researchers and academics by showcasing the potential of these methods to create extremely small holes. Microdrilling is critical for manufacturing miniaturized Nitinol components having applications in the medical field, robotics industry. Mechanical microdrilling offers a cost-effective and precise method over non-conventional ones. Thus, the model may identify the drilling performance's key process parameters. They can also help operators choose micro-drilling-optimal machining parameters. Modeling micro-drilling software helps in shaping an alloy.

Evaluation and Comparison of Dentin Thickness, Centering Ability, Canal Transportation, and Instrumentation Time of Pro AF Baby Gold and Pedoflex Files in Primary Root Canals Using a Cone Beam Computed Tomographic Analysis: An In Vitro Study.

Introduction: Pediatric rotary systems have the advantage of improved canal centricity and conservative canal preparation with better obturation quality. Pro AF Baby Gold and Pedoflex files are two exclusive pediatric rotary file systems that were introduced in recent times. Aim and objective: The aim of the present study is to compare and evaluate the dentine thickness, centering ability, canal transportation, and instrumentation time of Pro AF Baby Gold and Pedoflex files using cone beam computed tomography (CBCT). Materials and methods: A total of 40 extracted human primary molar teeth with a minimum 7 mm root length were included in the study and randomly divided into two groups: group I, Pro AF Baby Gold; group II, Pedoflex files. Teeth were imaged preoperatively with CBCT, then root canal preparation was done in both groups with respective files, followed by postoperative CBCT imaging to evaluate the dentin thickness, centering ability, and canal transportation of both groups. Instrumentation time was noted using a stopwatch. Results: There is a statistically significant difference in the instrumentation time; Pedoflex took a shorter time when compared to Pro AF Baby Gold files. Regarding canal transportation, there was no significant difference between the two files, with Pedoflex showing a better value than the other files. Regarding centering ability, there was no significant difference between the two files, with Pro AF Baby Gold having a better value than the other files (p < 0.001). Conclusion: From the findings of our present study, it was found that both systems were able to effectively shape curved root canals in terms of canal transportation and centering ability. How to cite this article: Busi S, PJ N, Deoghare A, et al. Evaluation and Comparison of Dentin Thickness, Centering Ability, Canal Transportation, and Instrumentation Time of Pro AF Baby Gold and Pedoflex Files in Primary Root Canals Using a Cone Beam Computed Tomographic Analysis: An In Vitro Study. Int J Clin Pediatr Dent 2024;17(8):892-897.

Quantitative evaluation of the apically extruded debris from root canals prepared by single-file rotary and reciprocating file systems: An in vitro study.

Aim: The aim is to investigate and compare the amount of apically extruded debris after root canal preparation using single rotary and reciprocating file system. Materials and Methods: Forty single-rooted human mandibular premolars with straight canals were randomly assigned to four groups (n = 10). The root canals were instrumented according to the manufacturers' instructions using single-rotary file systems Hyflex EDM (HEDM), One Shape (OS) and single-reciprocating file systems Wave OneGold (WOG) and OneRECI (OR). The apically extruded debris was collected in preweighed glass vials using the Myers and Montgomery method. After drying, the mean weight of the extruded debris was assessed using a microbalance. Results and Conclusions: Multiple comparison between groups demonstrated that the mean weight of apically extruded debris in the HEDM group was significantly less compared to all other study groups, and the differences were statistically significant (P < 0.001). Under the condition of this study, all file systems caused apical debris extrusion. The mean apically extruded debris was significantly least in HEDM, followed by WOG, OneRECI and highest in the OS group.

Dynamic analysis of a NiTi rotary file by using finite element analysis: Effect of cross-section and pitch length.

This study assessed stress distribution, maximum stress values and fatigue life of experimentally designed NiTi rotary files with different cross-sectional geometry and pitch length using finite element analysis (FEA). Four cross-sectional shapes (Convex triangle, S-shaped, Triple helix and Concave triangle) and two pitch lengths (2 mm and 3 mm) were tested in simulated root canals with curvatures of 30°, 45° and 60°. The FEA results indicated that convex triangle and triple helix geometries exhibited lower stress values compared to the S-shaped and concave triangle designs. Increasing the canal curvature angle resulted in higher stress values, with the S-shaped instrument showing the most significant increase (up to 12%). Instruments with shorter pitch lengths showed more even stress distribution enhancing fatigue life. The maximum stress was concentrated 5-8 mm from the tip, varying across cutting edges, with S-shaped sections experiencing the lowest forces but higher stress due to lower moments of inertia.

Cyclic fatigue resistance of two pediatric rotary files manufactured with different heat treatments: an in-vitro study.

Nickel-titanium (NiTi) instruments offer many advantages during endodontic instrumentation; however, the fracture risk within the canal remains a concern. Manufacturers continuously develop and introduce instruments to the market with supposedly enhanced cyclic fatigue resistance and increased flexibility, achieved through different proprietary manufacturing processes, the details of which have not been made public. In recent years, two rotary systems specially designed for deciduous teeth have been commercially available, but information about their performance is lacking. This investigation aimed to identify which manufacturing process provides better cyclic fatigue resistance: the AF-H Wire technology used in the AF baby rotary files (AF-f) or the CM-Wire technology used in the i3 Gold deciduous teeth rotary files (i3G-f). Forty rotary International Organization for Standardization (ISO) 25/04 files were tested in artificial canals with a standard geometry of 60° angle and 2.5 mm radius until fracture. The number of cycles to fracture was calculated, and the length of the fragments was measured. A scanning electron microscope (SEM) was used to examine the fracture surfaces and fragments. Energy dispersive spectroscopy (EDS) was used to determine the percentage weight of NiTi in each file. The statistical analysis (Mann-Whitney test) showed that the cyclic fatigue resistance of the AF-f was significantly higher (p < 0.0001) than that of the i3G-f. Additionally, there was a significant difference (p = 0.0419) in the length of the fractured fragments. All instruments showed one or more types of manufacturing defects and presented similar NiTi percentages by weight. The manufacturing process is critical to cyclic fatigue resistance, and there seems to be responsible for the difference in cyclic fatigue resistance between these similar instruments.

Apically extruded debris evaluation with the use of ProTaper Ultimate and TruNatomy files systems with and without glider preparation in primary tooth.

Information regarding the influence of resorption and glide paths on debris extrusion in primary teeth is lacking. Therefore, we evaluated debris extrusion with and without resorption and with and without the use of a path file in primary molar teeth prepared with ProTaper Ultimate (PTU) Prime and TruNatomy (TRN) Prime rotary file systems. Forty resorbed and forty non-resorbed primary molar teeth were collected. Both groups were divided into four subgroups (n = 10). The Eppendorf tubes were weighed pre-debris. The distal canals of the teeth were prepared with PTU Prime and TRN Prime file systems, with and without the use of path files. The debris-filled tubes were weighed, and the weight of only the extruded debris was calculated by subtraction. The data were analyzed using a three-way analysis of variance (ANOVA) test. The presence of tooth resorption significantly increased debris extrusion, and the use of a path file significantly decreased debris extrusion (p < 0.001). The binary and ternary interactions of the three evaluated parameters among the groups showed no significant differences in terms of the amount of debris extruded (p > 0.05). While debris extrusion was observed in all groups, the use of a glide path file in primary teeth before the preparation process resulted in less debris extrusion.

Comparative Analysis of the Frictional Resistance of Various Archwire-Ligature Combinations in Orthodontics.

Background: Frictional resistance is a critical factor influencing the efficacy of orthodontic treatment. Archwire-ligature combinations play a significant role in determining frictional forces within the orthodontic system. This study aimed to conduct a comparative analysis of the frictional resistance exhibited by various archwire-ligature combinations commonly used in orthodontics. Materials and Methods: A total of five archwire-ligature combinations were evaluated in this study: stainless steel archwire with elastic ligatures, stainless steel archwire with metal ligatures, nickel-titanium archwire with elastic ligatures, nickel-titanium archwire with metal ligatures, and beta-titanium archwire with metal ligatures. Frictional resistance was measured using a universal testing machine under standardized conditions, with a constant load applied to simulate clinical conditions. Results: The frictional resistance varied significantly among the different archwire-ligature combinations. The mean frictional resistance values (in arbitrary units) recorded were as follows: stainless steel archwire with elastic ligatures (X), stainless steel archwire with metal ligatures (Y), nickel-titanium archwire with elastic ligatures (Z), nickel-titanium archwire with metal ligatures (A), and beta-titanium archwire with metal ligatures (B). Statistical analysis revealed that combination A exhibited the lowest frictional resistance, followed by combination B, combination Z, combination X, and combination Y. Conclusion: The choice of archwire-ligature combination significantly affects the frictional resistance within the orthodontic system. Nickel-titanium archwires combined with metal ligatures demonstrated lower frictional resistance compared with stainless steel archwires, regardless of the ligature type. Among the combinations tested, nickel-titanium archwire with metal ligatures exhibited the lowest frictional resistance, suggesting its potential for reducing friction and improving treatment efficiency in orthodontic practice.

Conferring NiTi alloy with controllable antibacterial activity and enhanced corrosion resistance by exploiting Ag@PDA films as a platform through a one-pot construction route.

The lack of antibacterial activity and the leaching of Ni ions seriously limit the potential applications of the near equiatomic nickel-titanium (NiTi) alloy in the biomedical field. In this study, a silver nanoparticles (Ag NPs) wrapped in a polydopamine (Ag@PDA) film modified NiTi alloy with controllable antibacterial activity and enhanced corrosion resistance was achieved using a one-pot approach in a mixed solution of AgNO3 and dopamine. The controllable antibacterial activity could be achieved by adjusting the initial concentration of dopamine (Cdop), which obtained Ag@PDA films with varying thickness of polydopamine layers coated on Ag NPs, thereby conferring different levels of antibacterial activity to the modified NiTi alloy. In vitro antibacterial ratios (24 h) of Ag@PDA film-modified NiTi alloy against E.coli and S.aureus ranged from 46 % to 100 % and from 42 % to 100 %, respectively. The release curves of Ag ions indicated the persistent antibacterial effect of Ag@PDA film-modified NiTi alloy for at least 21 days. Moreover, in vitro cytotoxicity and in vivo implantation tests demonstrated the satisfactory biosafety of the Ag@PDA film-modified NiTi alloy when used as bioimplants. This research offers valuable insight into meeting various antibacterial demands for NiTi alloy implantations and highlights the potential of Ag-containing film-modified biomaterials in addressing different types of infections induced by implantations.

Semi-quantitative analysis on sea buckthorn phenolic-rich extract coating bone-like open porous NiTi-based alloy.

This study investigates the feasibility of coating Ni-Ti alloy with sea buckthorn extract via a hydrothermal method for targeted delivery of beneficial phenolic compounds to bone tissue. The qualitative analysis confirmed the presence of flavonoids and tannins in sea buckthorn extract, supporting its osteogenic potential. The microhardness of the NiTi alloy substrate was suitable for biomedical applications, and successful coating was achieved without compromising its properties. NiTi alloy samples were coated with 18.1, 20.1, and 12.4 mg of extract, respectively. Comprehensive evaluations confirmed the successful integration of the extract onto the alloy's surface. The coated system exhibited sustained release properties over five days, with the highest release occurring on the first day (on average 32.1 % for the first peak and 72.1 % for the second peak), as determined by HPLC analysis. The findings demonstrate the potential of this novel approach in developing dual-functionality implants for bone health promotion. Overall, this study underscores the promising potential of Ni-Ti alloy coated with sea buckthorn extract as a targeted drug delivery system for bone tissue.

A SEM/EDS evaluation of debris removal of used rotary Ni-Ti endodontic files by four different cleaning solutions.

Purpose: The aim of this study was to compare the efficacies levels of four cleaning solutions for removing debris from rotary Nickel-Titanium (Ni-Ti) endodontic instruments. Materials and methods: Twelve instruments that fractured during ex vivo instrumentation were used. Fractured surfaces were investigated by SEM before and after 3, 6 and 9 min of ultrasonic cleaning in 17 % EDTA.3NaOH (Group A), 2.5 % NaOCl (Group B), Dentasept 3H Rapide (Group C) and ZymeX™ (Group D) solutions. EDS analyses of selected files from all four groups of untreated and ultrasonically cleaned samples were performed to assess the elemental composition of the alloy surfaces. Results: SEM analysis revealed that after 9 min of ultrasonic agitation, all four investigated solutions had cleaned fractured surfaces. However, some low-atomic-number regions exhibited random distributions on the fractured surfaces. EDS analyses indicated that only C was retained on surface after 9 min of ultrasonic cleaning. This finding was common in all tested groups. Conclusions: All four investigated solutions substantially removed debris from the surfaces of the Ni-Ti files and were considered appropriate for clinical practice.

Effect of repetitive up-and-down movements on torque/force generation, surface defects and shaping ability of nickel-titanium rotary instruments: an ex vivo study.

BACKGROUND: The screw-in effect is a tendency of a nickel-titanium (NiTi) rotary endodontic file to be pulled into the canal, which can result in a sudden increase in stress leading to instrument fracture, and over-instrumentation beyond the apex. To reduce screw-in force, repeated up-and-down movements are recommended to distribute flexural stress during instrumentation, especially in curved and constricted canals. However, there is no consensus on the optimal number of repetitions. Therefore, this study aimed to examine how repeated up-and-down movements at the working length affect torque/force generation, surface defects, and canal shaping ability of JIZAI and TruNatomy instruments. METHODS: An original automated root canal instrumentation device was used to prepare canals and to record torque/force changes. The mesial roots of human mandibular molars with approximately 30˚ of canal curvature were selected through geometric matching using micro-computed tomography. The samples were divided into three groups according to the number of up-and-down movements at the working length (1, 3, and 6 times; n = 24 each) and subdivided according to the instruments: JIZAI (#13/0.04 taper, #25/0.04 taper, and #35/0.04 taper) or TruNatomy (#17/0.02 taper, #26/0.04 taper, and #36/0.03 tape) (n = 12 each). The design, surface defects, phase transformation temperatures, nickel-titanium ratios, torque, force, shaping ability, and surface deformation were evaluated. Data were analyzed with the Kruskal-Wallis and Dunn's tests (α = 0.05). RESULTS: The instruments had different designs and phase transformation temperatures. The 3 and 6 up-and-down movements resulted in a smaller upward force compared to 1 movement (p < 0.05). TruNatomy generated significantly less maximum torque, force, and surface wear than JIZAI (p < 0.05). However, TruNatomy exhibited a larger canal deviation (p < 0.05). No statistical differences in shaping ability were detected between different up-and-down movements. CONCLUSIONS: Under laboratory conditions with JIZAI and TruNatomy, a single up-and-down movement at the working length increased the screw-in force of subsequent instruments in severely curved canals in the single-length instrumentation technique. A single up-and-down movement generated more surface defects on the file when using JIZAI. TruNatomy resulted in less stress generation during instrumentation, while JIZAI better maintained the curvature of root canals.

Influence of distal-end heat treatment in the properties of heat-activated NiTi archwires.

PURPOSE: The aim of this study was to evaluate the extent of property changes caused by heating the distal portion of heat-activated nickel-titanium (NiTi) wires. METHODS: Forty preformed heat-activated NiTi archwires (3M Unitek, Monrovia, CA, USA) with a nominal cross-section of 0.018″ were used in this study. The archwires were divided into a control group, not submitted to heat treatment and, thus, maintaining the as-received properties, and an experimental group, in which the archwires were submitted to heat treatment for distal bending at one end. Wire segments of control and experimental groups were submitted to differential scanning calorimetry (DSC) and Vickers microhardness measurements. RESULTS: The DSC results suggest local recrystallization and precipitate dissolution at the heat-treated tip, which decreases as the distance to the wire's tip increases. Vickers microhardness tests revealed significant changes for distances between 6 and 8 mm from the wire's tip. Heating the distal portion of heat-activated NiTi archwires should be performed with care since this clinical procedure may compromise the performance of these wires to a distance of 8 mm from the archwire end. CONCLUSION: Heat treatment for distal bending in heat-activated NiTi archwires may be performed, with little impact on the areas adjacent to heat treatment. In cases presenting molars requiring significant orthodontic corrections, it should be preferred to apply other techniques to avoid archwire sliding, such as crimpable stops, or to have flame control to avoid placing a heat-treated section in the tubes of these molars.

Evaluation of apically extruded debris following glide-path preparation with different file systems.

The amount of apically extruded debris following glide-path preparation of mesial root of 120 freshly extracted human mandibular molar teeth using Senseus ProFinder files, PathFile, G-Files, Scout-RaCe files, HyFlex glidepath files and V glide-path two file system is of interest. The Eppendorf tubes were used as test equipment for collecting debris and the average weight of the debris was measured using an electronic micro-balancing system. It was observed that regardless of the file system utilized, debris was expelled from the apex. The G files resulted in a lower quantity of debris being extruded (0.070 ± 0.002 mg). In contrast, the V glide-path two file system exhibited the highest amount of debris extrusion (0.110 ± 0.004 mg) compared to all other file systems.

Comparative Analysis of Surface Roughness and Plastic Deformation of Reciprocating Instruments after Clinical Use.

This study assessed the surface topography and plastic deformation (PD) of new and used contemporary reciprocating instruments. Twenty-six WaveOne Gold (WOG) and EdgeOne Fire (EO) instruments were photographed under magnification. The instruments were randomly assigned to a control group of new instruments preserved for surface roughness analysis (n = 6 each), or to an experimental group to shape the root canal system of a single molar (n = 20 each), making a total of four groups (WOGnew, EOnew, WOGused, EOused). Used instruments were also photographed after instrumentation. The presence of fractures was registered. Preoperative and postoperative images were randomly ordered for evaluation. Two blinded calibrated examiners evaluated the presence of PD. Inter-observer agreement was calculated with the Kappa coefficient (K = 0.89). 3D profilometry was also used for the surface roughness analysis of six randomly selected instruments from the WOGused and EOused groups. Chi-square and two-way ANOVA tests were used to, respectively, compare PD and changes in surface roughness among the groups. No instruments fractured; however, a significantly greater percentage of EO instruments suffered plastic deformation than WOG instruments (p < 0.001), (OR = 11.09 (CI 95% 2.6-56.3)). The overall surface roughness was higher for most parameters in the EO instruments (p < 0.05). Single uses of EO instruments produced significantly higher chances of PD and increased surface roughness values compared to WOG.

Research on NiTi instruments combined with ultrasonic irrigation and multiantibiotic paste in root canal therapy of periapical inflammation in deciduous teeth.

Pain often occurs after root canal treatment due to unavoidable mechanical or chemical damage. The purpose of the present study was to investigate the efficacy of a nickel-titanium (NiTi) device combined with ultrasonic irrigation and multiple antibiotic creams in the treatment of periapical inflammation of deciduous teeth, so as to improve the understanding of root canal treatment and optimize clinical practice. Evaluation of efficacy was conducted using X-rays and the Visual Analog Scale. This treatment significantly reduced pain and also improved patient compliance and treatment outcomes. The findings of the present study may have scientific and clinical significance for optimizing root canal treatment in pediatric dentistry and requires further in-depth research in clinical practice. These outcomes may provide potential new ideas and directions for improving patients' quality of life and the efficacy of clinical treatment and have further impacts on future related research and medical practice.

Extrusion of debris during retreatment using various nickel-titanium files in teeth with simulated lateral root perforation.

PURPOSE: To investigate the influence of various nickel-titanium (Ni-Ti) files on debris extrusion during the retreatment of teeth with simulated lateral root perforation, focusing on root resorption. METHODS: Sixty human mandibular premolar teeth were divided into groups with and without perforation and further subdivided based on the retreatment technique. Lateral root perforations were created in one group (Group 1), while the other group had no perforations (Group 2). Two retreatment techniques were compared: Remover (RE)+One RECI (OR) and ProTaper Universal Retreatment (PTUR)+WaveOne Gold (WOG). The weight of the extruded debris was determined. The time of both retreatment procedures was measured. Statistical analyses were performed using a two-way analysis of variance (ANOVA) test (P < 0.05). RESULTS: Teeth with simulated lateral root perforation exhibited higher extrusion of debris during retreatment. In both groups, RE+OR files led to more extruded debris than PTUR+WOG files. However, this difference was statistically significant in Group 2 (P < 0.001). Compared to PTUR+WOG files, RE+OR files showed a statistically significant longer time to remove obturation material (P < 0.001). CONCLUSION: Perforated teeth exhibited significantly higher debris extrusion. While both file systems demonstrated similar debris extrusion in perforated teeth, the RE+OR files significantly increased debris extrusion in non-perforated teeth compared to the PTUR+WOG files.

Novel approach for characterizing clinical load application of superelastic orthodontic wires.

OBJECTIVE: Current standardized in vitro bending experiments for orthodontic archwires cannot capture friction conditions and load sequencing during multi-bracket treatment. This means that clinically relevant forces exerted by superelastic wires cannot be predicted. To address these limitations, this study explored a novel test protocol that estimates clinical load range. METHODS: The correction of a labially displaced maxillary incisor was simulated using an in vitro model with three lingual brackets. Deflection force levels derived from four different protocols were designed to explore the impact of friction and wire load history. These force levels were compared in nickel-titanium (NiTi) archwires with three commonly used diameters. The unloading path varied between protocols, with single or multiple sequences and different load orders and initial conditions. RESULTS: Deflection forces from the new protocol, employing multiple continuous load/unload cycles (CCincr), consistently exceeded those from the conventional protocol using a single continuous unloading path (CUdecr). Mean differences in plateau force ranged from 0.54 N (Ø 0.014" wire) to 1.19 N (Ø 0.016" wire). The CCinr protocol also provided average force range estimates of 0.47 N (Ø 0.012" wire), 0.89 N (Ø 0.014" wire), and 1.15 N (Ø 0.016" wire). SIGNIFICANCE: Clinical orientation towards CUdecr carries a high risk of excessive therapeutic forces because clinical loading situations caused by friction and load history are underestimated. Physiological tooth mobility using NiTi wires contributes decisively to the therapeutic load situation. Therefore, only short unloading sequences starting from the maximum deflection in the load history, as in CCincr, are clinically meaningful.

Exploring the Potential of MIM-Manufactured Porous NiTi as a Vascular Drug Delivery Material.

Porous nickel-titanium (NiTi) manufactured using metal injection molding (MIM) has emerged as an innovative generation of drug-loaded stent materials. However, an increase in NiTi porosity may compromise its mechanical properties and cytocompatibility. This study aims to explore the potential of porous NiTi as a vascular drug delivery material and evaluate the impact of porosity on its drug loading and release, mechanical properties, and cytocompatibility. MIM, combined with the powder space-holder method, was used to fabricate porous NiTi alloys with three porosity levels. The mechanical properties of porous NiTi were assessed, as well as the surface cell growth capability. Furthermore, by loading rapamycin nanoparticles onto the surface and within the pores of porous NiTi, we evaluated the in vitro drug release behavior, inhibitory effect on cell proliferation, and inhibition of neointimal hyperplasia in vivo. The results demonstrated that an increase in porosity led to a decrease in the mechanical properties of porous NiTi, including hardness, tensile strength, and elastic modulus, and a decrease in the surface cell growth capability, affecting both cell proliferation and morphology. Concurrently, the loading capacity and release duration of rapamycin were extended with increasing porosity, resulting in enhanced inhibitory effects on cell proliferation in vitro and inhibition of neointimal hyperplasia in vivo. In conclusion, porous NiTi holds promise as a desirable vascular drug delivery material, but a balanced consideration of the influence of porosity on both mechanical properties and cytocompatibility is necessary to achieve an optimal balance among drug-loading and release performance, mechanical properties, and cytocompatibility.

Robot-Assisted Correction of a Supra-Long Tracheal Stenosis Using C-Type Nickel-Titanium Alloy Exterior Stenting and Suspension Fixation Technique: A Case Report.

T-tubes and airway stents are commonly used but have limited effectiveness and frequent complications. A 50-year-old male patient presented with severe tracheal stenosis, affecting an 8.7 cm length of the airway. We employed an innovative approach known as external suspension fixation of tracheal stent using robotic assistance. This method involves surgically attaching the stent to the exterior of the trachea to provide support and stabilize the softened or collapsed tracheal segments. We designed a C-shaped nickel-titanium alloy exterior stent and successfully fixed it using robotic assistance. This intervention effectively restored tracheal function and led to a favorable postoperative recovery. The technique does not affect tracheal membrane function or airway mucociliary clearance. It could potentially be considered as a new option for treating long-segment benign tracheal softening or collapse.

Fifteen years of engine-driven nickel-titanium reciprocating instruments, what do we know so far? An umbrella review.

Numerous systematic reviews (SRs) have produced conflicting findings on engine-driven nickel-titanium reciprocating instruments (reciprocating instruments) since Yared's seminal study 15 years ago. This umbrella review analysed SRs examining the clinical and laboratory evidence regarding reciprocating instruments for root canal treatment. SRs that evaluated qualitatively and/or quantitatively the outcomes postoperative pain, oral health-related quality of life (OHRQoL), shaping ability, debris extrusion, microbial load, endotoxins reduction, cyclic fatigue, file fracture, dentinal cracks and root canal filling removal were included. The AMSTAR 2 tool was used to evaluate SRs quality, while the ROBIS tool to assess risk of bias (RoB). Forty SRs were included. The SRs revealed predominantly 'high' RoB and 'critically low' quality. Most focused on technical outcomes, exhibiting significant methodological and statistical heterogeneity. Findings suggest comparable efficacy between reciprocating and rotary instruments. However, due to the scarcity of high-quality evidence, future well-designed studies and reviews considering core outcome measures are needed.