[Analysis of clinical and endoscopic characteristics of colorectal polyps in children].

To analyze the clinical and endoscopic characteristics of colorectal polyps in children, and to explore the detection rate, age and gender distribution characteristics, endoscopic treatment effect and follow-up monitoring of colorectal polyps in children, so as to provide reference for disease management of colorectal polyps in children. The clinical and endoscopic characteristics of children with colorectal polyps in Xi 'an Children's Hospital from January 2019 to December 2019 were retrospectively analyzed. The patients were divided into 5 groups according to age (y): 0

[Preoperative serum creatinine as an independent prognostic biomarker in patients with early-stage cervical adenocarcinoma].

Objective: To investigate the effect of preoperative serum creatinine (Scr) level on the prognosis of patients with early cervical adenocarcinoma (ADC) and its predictive value. Methods: A retrospective review was performed on 199 patients with the International Federation of Gynecology and Obstetrics (FIGO) stage ⅠA1-ⅡA1 and pathology-proven invasive ADC from January 2005 to December 2015. Patients were followed up by phone and outpatient, with a median follow-up time 77.5 (57.0, 114.0) months, 11 cases (5.5%) were missing, 19 cases (10.1%) recurred, and 17 cases (9.0%) died. Multivariate analysis was performed by Cox regression model to analyze the related factors of the prognosis of ADC patients. The optimal cut-off point was determined by the analysis of receiver operating characteristics (ROC), and the predictive value of related factors for prognosis was evaluated by the area under the curve (AUC). Results: The median age of 199 patients was 44.0 (39.0-50.0) years. Overall, 16 patients (8.0%) were stage ⅠA1; 4 patients (2.0%) were stage ⅠA2; 147 patients (74.0%) were stage ⅠB1; 13 patients (6.5%) were stage ⅠB2; 19 patients (9.5%) were stage ⅡA1. The multivariate analysis showed that FIGO stage [4.570 (1.625-12.854)] and elevated Scr [1.065 (1.006-1.128)] were correlated with DFS in patients with early ADC, as well as correlated with OS [4.412 (1.458-13.350) and 1.076 (1.012-1.144), respectively (all P<0.05)]. The optimal cut-off point of Scr level was 75.2 µmoI/L. The AUC showed that the Scr level was a predictor of DFS (AUC=0.677, 95%CI: 0.608-0.742, P=0.006) and OS (AUC=0.677, 95%CI: 0.607-0.741, P=0.012). Conclusions: The preoperative Scr level independently predicts the prognosis of early-stage ADC; patients with Scr levels>75.2 µmoL/L might require more follow-up and adjuvant treatment, as they might have a poorer prognosis.

[Multimodal Magnetic Resonance and Fluorescence Imaging of the Induced Pluripotent Stem Cell Transplantation in the Brain].

The understanding of the engrafted cell behaviors such as the survival, growth and distribution is the prerequisite to optimize cell therapy, and a multimodal imaging at both anatomical and molecular levels is designed to achieve this goal. We constructed a lentiviral vector carrying genes of ferritin heavy chain 1 (FTH1), near-infrared fluorescent protein (iRFP) and enhanced green fluorescent protein (egfp), and established the induced pluripotent stem cells (iPSCs) culture stably expressing these three reporter genes. These iPSCs showed green and near-infrared fluorescence as well as the iron uptake capacity in vitro. After transplanted the labeled iPSCs into the rat brain, the engrafted cells could be in vivo imaged using magnetic resonance imaging (MRI) and near-infrared fluorescent imaging (NIF) up to 60 days at the anatomical level. Moreover, these cells could be detected using EGFP immunostaining and Prussian blue stain at the cellular level. The developed approach provides a novel tool to study behaviors of the transplanted cells in a multi-modal way, which will be valuable for the effectiveness and safety evaluation of cell therapy.

[Transoral endoscopic resection of benign tumors in parapharyngeal space via medial pterygomandibular raphe approach].

Objective: To explore the surgical methods and effects of transoral endoscopic resection of benign tumors in parapharyngeal space via medial pterygomandibular raphe approach. Methods: The clinical data of 23 patients who underwent resection of benign tumors in parapharyngeal space by endoscopic medial pterygomandibular raphe approach from January 2016 to July 2020 in the Department of Otorhinolaryngology Head and Neck Surgery, the Affiliated Hospital of Qingdao University were analyzed retrospectively. There were 14 males and 9 females with a median age of 43 years. The tumors were located in the anterior space of the styloid process in 13 cases and in the posterior space in 10 cases. The smallest tumor volume was 7.3 ml and the largest was 80.2 ml. The preoperative imaging features, the characteristics and risks of this approach in the operation were analyzed, and the feasible mode of operation was explored. Results: All patients completed the operation successfully. The intraoperative blood loss was 20 to 50 ml, with an average of 28.3 ml. The operation time was 40 to 110 min, with an average of 75.4 min. The incision length was 2 to 4 cm, with an average of 3.0 cm. The postoperative pain score was 2 to 4, with an average of 3.2. The postoperative hospital stay was 4 to 9 d, with an average of 6.7 d. Postoperative pathological diagnosis included pleomorphic adenoma (n=12), neurilemmoma (n=10) and basal cell adenoma (n=1). The patients were followed up for 6 to 60 months. There was no postoperative complication such as infection or serious bleeding, and there was no tumor recurrence after operation. Conclusion: Endoscopic resection of benign tumor in parapharyngeal space via medial pterygomandibular raphe approach is a safe, effective, and minimally invasive surgical method for the treatment of tumors in parapharyngeal space.

[Clinical application of expanded noninvasive prenatal testing for fetal chromosome abnormalities].

To assess the positive predictive value (PPV) of extended noninvasive prenatal testing (NIPT-plus) for fetal chromosomal abnormalities. This retrospective research enrolled 511 cases of pregnant women with positive NIPT-plus results at the Obstetrics and Gynecology Hospital of Fudan University from May 2017 to January 2021. Karyotype analysis and chromosome microarray analysis (CMA) techniques was applied for verification. All cases were followed to determine their pregnancy outcome. The Chi-square test was used in PPV. 63 out of 511 refused prenatal diagnosis after counseling, 448 pregnant women with prenatal diagnosis showed that the PPVs of NIPT-plus test for fetal trisomy 21, 18 and 13 (T21, T18, T13), sex chromosome aneuploidy (SCAs) and chromosome microdeletion/microduplication syndrome (MMS) were 86.0% (92/107), 79.5% (35/44), 54.5% (12/22), 39.5% (75/190), and 41.7% (30/72), respectively. The results revealed that the PPV was higher among older pregnant women compared to young pregnant women (77.8% vs. 51.9%,P<0.01). With increasing maternal age, the PPV of NIPT-plus presented increasing trends for T21, T13, and composite PPV except for T18 or SCAs. In addition, the termination rates for confirmed SCAs fetal karyotypes 45, X; 47, XXX; 47, XXY and 47, XYY were 11/11, 3/15, 91.7% (22/24) and 1/14, respectively. NIPT-plus can safely and effectively detect fetal chromosomal abnormalities and can be extended to MMS screening, significantly reducing the proportion of interventional prenatal diagnoses, and those with positive screening still require further confirmation.

[Application of artificial intelligence-assisted diagnosis for cervical liquid-based thin-layer cytology].

Objective: To explore the application value of artificial intelligence-assisted diagnosis system for TBS report in cervical cancer screening. Methods: A total of 16 317 clinical samples and related data of cervical liquid-based thin-layer cell smears, which were obtained from July 2020 to September 2020, were collected from Southern Hospital, Guangzhou Huayin Medical Inspection Center, Shenzhen Bao'an People's Hospital(Group) and Changsha Yuan'an Biotechnology Co., Ltd. The TBS report artificial intelligence-assisted diagnosis system of cervical liquid-based thin-layer cytology jointly developed by Southern Medical University and Guangzhou F. Q. PATHOTECH Co., Ltd. based on deep learning convolution neural network was used to diagnose all clinical samples. The sensitivity,specificity and accuracy of both artificial intelligence-assisted diagnosis system and cytologists using artificial intelligence-assisted diagnosis system were analyzed based on the evaluation standard(2014 TBS). The time spent by the two methods was also compared. Results: The sensitivity of artificial intelligence-assisted diagnosis system in predicting cervical intraepithelial lesions and other lesions (including endometrial cells detected in women over 45 years old and infectious lesions) under different production methods, different cytoplasmic staining and different scanning instruments was 92.90% and 83.55% respectively, and the specificity of negative samples was 87.02%, while that of cytologists using artificial intelligence-assisted diagnosis system was 99.34%, 97.79% and 99.10%, respectively. Moreover, cytologists using artificial intelligence-assisted diagnosis system could save about 6 times of reading time than manual. Conclusions: Artificial intelligence-assisted diagnosis system for TBS report of cervical liquid-based thin-layer cytology has the advantages of high sensitivity, high specificity and strong generalization. Cytologists can significantly improve the accuracy and work efficiency of reading smears by using artificial intelligence-assisted diagnosis system.

Transcriptome analysis reveals TOR signalling-mediated plant flush shoots governing Diaphorina citri Kuwayama oviposition.

Asian Citrus Psyllid (ACP), Diaphorina citri, is a key vector transmitting the causative agent of Huanglongbing (HLB) disease. Population growth of ACP is evident after feeding on plant flush shoots, as they only oviposit here. However, the underlying mechanism as to why flush shoots govern oviposition is unclear. This study compares the fecundity and ovarian morphology of ACP between young flush and mature leaves. Furthermore, the transcriptome of mated females infesting Murraya paniculata was analysed. Finally, the gene of the key Target of Rapamycin (TOR) signalling pathway was silenced by RNAi. Results indicated that flush shoot feeding activated the development of the psyllids ovary and therefore induced oviposition. A total of 126 and 2794 differentially expressed genes were detected at 1 and 5 days, respectively, after pest infestation of flush shoots compared to mature leaves. Many genes are involved in protein metabolism, Mitogen-Activated Protein Kinase (MAPK) signalling pathway, hormone synthesis, and TOR signalling pathway: all thought to activate reproduction. Silencing of the positive regulator gene DcRheb in the TOR pathway resulted in lower levels of ecdysone and juvenile hormone and decreased vitellogenin synthesis, further disrupting reproductive ability. This study enhances understanding of the molecular mechanism underlying ACP's reproductive strategy.

[Epidemiological characteristics and risk factors of Blastocystis hominis infection among patients with HIV/AIDS in Fuyang City Anhui Province].

OBJECTIVE: To investigate the prevalence and risk factors of Blastocystis hominis infections among patients with HIV/AIDS in Fuyang City, Anhui Province. METHODS: A cross-sectional study was conducted in Fuyang City, Anhui Province in 2016. The demographic and socioeconomic status, and the lifestyle and production style were collected using a questionnaire survey. B. hominis DNA was detected in subjects'stool samples using a PCR assay, and the CD4+ T lymphocyte count and HIV viral load were measured in the subjects' blood samples. The risk factors of B. hominis infections among patients with HIV/AIDS were identified using univariate and multivariate logistic regression analyses. RESULTS: A total of 398 HIV/AIDS patients were enrolled in this study, with a mean age of 49.3 years, a mean body weight of 55.9 kg and a mean height of 164.4 cm. The prevalence of B. hominis infection was 6.78% in the study subjects, and no gender- (χ2 = 1.589, P = 0.207), education level- (χ2 =0.508, P = 0.776), marital status- (χ2 = 0.419, P = 0.811) or occupation-specific prevalence (χ2 = 2.744, P = 0.615) was detected. Among the patients with HIV/AIDS, there were no significant differences in the age (t = 0.370, P = 0.712), height (t = 1.587, P =0.113), body weight (t = 0.516, P = 0.606), CD4+ T lymphocyte count (t = 1.187, P = 0.230) or HIV viral load (t = 0.193, P =0.496) between B. hominis-infected and uninfected individuals. Dinking non-tap water [OR = 6.554, 95% CI: (1.876 to 22.903)] and keeping dogs [OR = 5.895, 95% CI: (2.017 to 17.225)] were identified as risk factors for B. hominis infection in patients with HIV/AIDS. CONCLUSIONS: The prevalence of B. hominis infection is high in HIV/AIDS patients, and drinking non-tap water and keeping dogs are risk factors for B. hominis infection among HIV/AIDS patients.

Serial T-SPOT.TB in household contacts of tuberculosis patients: a 6-year observational study in China.

BACKGROUND: Screening tuberculosis (TB) contacts is a priority for TB control; however, it remains inadequate in most regions of China.OBJECTIVE: To investigate the progression of latent TB infection (LTBI) using the interferon-gamma release assay (IGRA) in contacts of active TB patients.DESIGN: This longitudinal prospective observational study included 159 household contacts aged ≥14 years without preventive treatment who were followed up for 6 years to compare their conversion and reversion rates using the T-SPOT®.TB IGRA to diagnose LTBI.RESULTS: Among the 159 household contacts, LTBI positivity was 47.5%. Age was independently associated with LTBI (OR 3.6, 95%CI 1.81-7.14; P = 0.00). T-SPOT.TB conversion rates were respectively 29.4% and 18.8% at 3- and 6-year follow-up. The reversion rates were 9.4% of contacts during the 3-year follow-up period, which increased to 38.2% at the 6-year follow-up. A decreasing trend in spot-forming cells on T-SPOT.TB was observed in most patients at the 6-year follow-up.CONCLUSION: LTBI prevalence among household contacts was relatively high, particularly in elderly patients. Furthermore, serial IGRA testing was highly dynamic; however, this overall trend gradually decreased over time, even if preventive therapy was not prescribed.

Preparation of icariin/TiO2 nanotube composite coating on pure titanium surface and analysis of early drug release.

The article "Preparation of icariin/TiO2 nanotube composite coating on pure titanium surface and analysis of early drug release" by F.-F. Wang, Y. Li, H.-C. Liu, published in Eur Rev Med Pharmacol Sci 2019; 23(5): 1864-1873 has been withdrawn.

CAFs secreted exosomes promote metastasis and chemotherapy resistance by enhancing cell stemness and epithelial-mesenchymal transition in colorectal cancer.

BACKGROUND: Cancer associated fibroblasts (CAFs) are key stroma cells that play dominant roles in tumor progression. However, the CAFs-derived molecular determinants that regulate colorectal cancer (CRC) metastasis and chemoresistance have not been fully characterized. METHODS: CAFs and NFs were obtained from fresh CRC and adjacent normal tissues. Exosomes were isolated from conditioned medium and serum of CRC patients using ultracentrifugation method and ExoQuick Exosome Precipitation Solution kit, and characterized by transmission electronic microscopy, nanosight and western blot. MicroRNA microarray was employed to identify differentially expressed miRNAs in exosomes secreted by CAFs or NFs. The internalization of exosomes, transfer of miR-92a-3p was observed by immunofluorescence. Boyden chamber migration and invasion, cell counting kit-8, flow cytometry, plate colony formation, sphere formation assays, tail vein injection and primary colon cancer liver metastasis assays were employed to explore the effect of NFs, CAFs and exosomes secreted by them on epithelial-mesenchymal transition, stemness, metastasis and chemotherapy resistance of CRC. Luciferase report assay, real-time qPCR, western blot, immunofluorescence, and immunohistochemistry staining were employed to explore the regulation of CRC metastasis and chemotherapy resistance by miR-92a-3p, FBXW7 and MOAP1. RESULTS: CAFs promote the stemness, epithelial-mesenchymal transition (EMT), metastasis and chemotherapy resistance of CRC cells. Importantly, CAFs exert their roles by directly transferring exosomes to CRC cells, leading to a significant increase of miR-92a-3p level in CRC cells. Mechanically, increased expression of miR-92a-3p activates Wnt/ß-catenin pathway and inhibits mitochondrial apoptosis by directly inhibiting FBXW7 and MOAP1, contributing to cell stemness, EMT, metastasis and 5-FU/L-OHP resistance in CRC. Clinically, miR-92a-3p expression is significantly increased in CRC tissues and negatively correlated with the levels of FBXW7 and MOAP1 in CRC specimens, and high expression of exosomal miR-92a-3p in serum was highly linked with metastasis and chemotherapy resistance in CRC patients. CONCLUSIONS: CAFs secreted exosomes promote metastasis and chemotherapy resistance of CRC. Inhibiting exosomal miR-92a-3p provides an alternative modality for the prediction and treatment of metastasis and chemotherapy resistance in CRC.

Preparation of icariin/TiO2 nanotube composite coating on pure titanium surface and analysis of early drug release.

OBJECTIVE: The surface modification of pure titanium and the improvement of the early osseointegration of titanium implants are research hotspots currently. This study aimed to load icariin onto the surface of TiO2 nanotube to form the composite coating, and to study the amount of loaded drug and the importance of early release. MATERIALS AND METHODS: The TiO2 nanotube was formed on the surface of smooth pure titanium via anodic oxidation, and both smooth pure titanium and TiO2 nanotube were characterized using the scanning electron microscope, atomic force microscope and contact angle apparatus. Moreover, icariin was loaded onto the surface of pure titanium and TiO2 nanotube using the soaking method. RESULTS: The amount of early drug release in both types of materials was determined via high-performance liquid chromatography. The amount of loaded drug was calculated, and the curves of cumulative release amount and cumulative release percentage were plotted. The TiO2 nanotube had a diameter of 80 nm with greater roughness than that of pure titanium (p<0.05) and smaller contact angle than that of pure titanium (p<0.05). The cumulative drug release amount in the first 14 d and the curve of cumulative drug release in the first 4 h in icariin/TiO2 nanotube group were significantly larger and higher than those in the icariin/pure titanium group. The curve of cumulative drug release percentage was flatter and the release time was longer in icariin/TiO2 nanotube group than those in the icariin/pure titanium group. CONCLUSIONS: Our results indicate that the icariin/TiO2 nanotube composite coating can provide a higher drug loading amount with a sustained-release effect.

[Relationship between impaired myocardial untwisting and left ventricular diastolic dysfunction in patients with autoimmune diseases].

Objective: To observe the relationship between impaired myocardial untwisting and left ventricular diastolic dysfunction in patients with autoimmune diseases (AD). Methods: In this retrospective study, 95 AD patients (27 males, (38.6±14.2) years old) were enrolled as AD group and 71 gender and age matched healthy subjects (24 males, (37.6±12.2) years old) were enrolled as control group, all underwent transthoracic echocardiography and two-dimensional speckle-tracking echocardiography (STE) in our hospital between January 2014 and June 2018. Left ventricular untwisting and diastolic function parameters were measured. Multiple logistic regression analysis was used to identify related factors of left ventricular diastolic dysfunction in AD patients. Receiver operating characteristic (ROC) curve was used to identify the diagnosis value of untwisting parameters for left ventricular diastolic dysfunction in AD patients. Results: Compared with control group, left ventricular ejection fraction was lower (58(47, 66)% vs. 67 (62, 71) %, P<0.001), E/e' was higher (10.78 (7.28, 13.65) vs. 6.30 (5.55, 7.25) , P<0.001), isovolumic relaxation time was longer (73.5 (56.5, 88.0) ms vs. 62.0 (58.0, 68.5) ms, P<0.001),and untwist slope during isovolumic relaxation period (USIR) was lower (31.92 (14.09, 54.92) °/s vs. 59.90 (40.09, 87.18) °/s, P<0.001) in AD group than in control group. Multiple logistic regression analysis showed heart rate (OR=0.885, 95%CI 0.840-0.931, P<0.001), E/e' (OR=0.655, 95%CI 0.537-0.798, P<0.001) and USIR (OR=0.986, 95%CI 0.974-0.998, P=0.020) were independently related with left ventricular diastolic dysfunction in AD patients. ROC curve showed that area under the curve (AUC) was 0.919 (P<0.001), sensitivity was 87.6%, and specificity was 88.7%, when combining the heart rate, E/e', and USIR as assessment parameters for the diagnosis of left ventricular diastolic dysfunction in AD patients at a cutoff of 0.51. Conclusions: Impairment of myocardial untwisting indicates the presence of early stage left ventricular diastolic dysfunction in AD patients. USIR may be a sensitive parameter to evaluate early stage left ventricular diastolic dysfunction in AD patients.

A study on PLGA sustained release icariin/titanium dioxide nanotube composite coating.

OBJECTIVE: The Chinese medicine icariin with osteoinduction and osteogenesis abilities is loaded onto the surface of TiO2 nanotubes to form icariin/TiO2 nanotube composite coating, which can synergistically enhance the osseointegration around the implant. MATERIALS AND METHODS: However, the half-life of icariin is short, and the sustained release effect of TiO2 nanotubes cannot meet the long-term stable drug release requirement. Therefore, in order to enhance the sustained release effect of icariin/TiO2 nanotube composite coating, in this study, polymer PLGA was applied to the composite coating by overlay method and mixing method. Scanning electron microscopy and release detection were performed to study the effects of two PLGA loading methods on the loading and early release of composite coatings. RESULTS: Results showed that the PLGA loading and sustained release effect was stronger than that of TiO2 nanotubes. The sustained release effect was mainly manifested in the rapid release phase. The release time of the TiO2nanotube drug-loaded composite coating was 9 days. Overlay method and mixing method extended the drug release time to 12 d and 10 d, respectively. CONCLUSIONS: Therefore, PLGA can enhance the loading and sustained release properties of icariin/TiO2 nanotube composite coating. Overlay method has better sustained release effect, and the mixing method has better loading performance.

[Construction and mechanical analysis of finite element model for bending property of controlled memory wire nickel-titanium rotary file].

OBJECTIVE: To construct a model for a controlled memory (CM) nickel-titanium (NiTi) file and another M-wire NiTi file with the same geometry by using finite element analysis. To evaluate the flexibility of a CM NiTi file by using three dimensional finite element method and to compare its mechanical responses with that M-wire NiTi. METHODS: Based on the reverse engineering, the 21 mm long, 25#/08 taper Hyflex NT NiTi file and Hyflex CM NiTi file were fixed by the cantilever bending model at a distance of 9.5 mm from the tip of the file. The mechanical tester's indenter was loaded/unloaded at a distance of 3 mm from the tip of the file. The maximum displacement was 3 mm, the load displacement curve was obtained. Subsequently, by using a micro-CT to scan (layer spacing of 8 µm) NiTi files, and ABAQUS (6.10) was introduced to construct a geometric model. Hyflex NT was considered as a shapememory alloy constitutive model, Hyflex CM was considered as a power-hardening plastic constitutive model, respectively. Comparing the load-displacement curve of cantilever bending in the three-dimensional finite element model with the load-displacement curve in the experiment. RESULTS: Two tetrahedral element models were constructed, the total number of nodes was 99 353 and the total number of cells was 63 744. When the loading displacement was 1 mm, the stress distribution of the cross section at 6.1 mm from the tip of the file was observed. The upper and lower surfaces were subjected to the maximum bending stress and entered the phase transformation yield stage. The finite element simulation could clearly show the deformation of the file. Various information such as deformation characteristics and stress distribution in the process were well fitted to the actual experimental curve. CONCLUSION: The constitutive behavior of the material has a significant effect on the mechanical behavior of NiTi file. The finite element model established for the NiTi file of the CM wire can accurately capture the characteristics of various deformation processes of the NiTi root canal file, and it has a good fit with the actual experimental curve. The finite element model can be used for study on bending properties of CM wire.

Downregulation of hsa_circ_0000285 serves as a prognostic biomarker for bladder cancer and is involved in cisplatin resistance.

Bladder cancer remains a very challenging disease to treat with the high rates of recurrence and progression associated with current therapies. Although the association between bladder cancer pathology and circRNAs remains undetermined, circRNAs signatures may be useful as prognostic and predictive factors and clinical tools for assessing disease state, treatment response and outcome. This study investigates if these circRNAs can be used as biomarkers for bladder cancer diagnosis and predicting treatment response. Herein, qPCR measured the expression of hsa_circRNA_100783, hsa_circ_0000285 and hsa_circRNA_100782 in bladder cancer tissues. It was established that sa_circ_0000285, but not hsa_circRNA_100782 and hsa_circRNA_10078, are significantly reduced in bladder cancer tissues and serum compared to adjacent tissues and healthy controls. Moreover, hsa_circ_0000285 expression was lower in cisplatin-resistant bladder cancer patients than in those who were cisplatin-sensitive. Here, hsa_circ_0000285 was associated with tumor size (p<0.001), differentiation (p<0.001), lymph node metastasis (p=0.038), distant metastasis (p=0.004) and TNM stage (p=0.013). Further analysis showed that hsa_circ_0000285 would be an independent prognostic factor for bladder cancer patient outcome. In conclusion, our study indicates hsa_circ_0000285 may be a novel biomarker for bladder cancer because of its involvement in bladder cancer chemo-sensitivity.

[Surface microstructure and cyclic fatigue resistance of electro discharged machining nickel-titanium endodontic instrument].

OBJECTIVE: To compare the surface microstructures and cyclic fatigue resistance of HyFlex EDM with HyFlex CM and HyFlex NT. METHODS: Twelve 25 mm-long 25#/- HyFlex EDM and twelve 25 mm-long 25#/0.06 taper HyFlex CM or HyFlex NT were selected. The surface microstructure of the 2 instruments which were randomly selected from each group was observed by using scanning electron microscope (SEM). The remaining 10 instruments from each group were submitted to the cyclic fatigue test by using a simulated stainless steel root canal with 60° angle of curvature and curvature radius of 3.5 mm. The time till fracture was recorded, the number of cyclic fatigue (NCF) was calculated, the length of fracture fragment was evaluated, and the topographic features were analyzed by using SEM. The data were analyzed by using one-way analysis via SPSS 23.0 software. The statistical significance level was set at 0.05. RESULTS: SEM observation of the surface and microstructural characterization revealed peculiar melting appearance and evenly distributed micropores on the surface of HyFlex EDM while observations of the surface of both HyFlex CM and HyFlex NT demonstrated machining grooves and irregularities. The NCF of HyFlex EDM was 838±223, which was significantly higher than not only that of HyFlex CM (582±99), but also that of HyFlex NT (81±20) (P<0.05), and the difference between the latter two groups was significant, as well (P<0.05). The length of fractured fragments of HyFlex EDM was (7.27±0.28) mm, which was significantly longer than the HyFlex CM and HyFlex NT, with values of (6.72±0.26) mm and (6.62±0.37) mm, respectively (P<0.05). Topographic features demonstrated typical cyclic fatigue for all the three groups while the region of crack origins was more for HyFlex EDM and HyFlex CM than that of HyFlex NT. As far as the dimple area was concerned, that of HyFlex EDM was deeper and larger than that of HyFlex CM and HyFlex NT. CONCLUSION: Within the limitations of this study, electro-discharge machining leads to peculiar melting appearance with micropores instead of machining grooves and irregularities on the surface of HyFlex EDM, which may be the reason why HyFlex EDM exhibits significantly better cyclicfatigue resistance than HyFlex CM and HyFlex NT.