1.Preliminary application of histological evaluation of donor pancreas biopsy tissue in simultaneous pancreas-kidney transplantation
Jiao WAN ; Hui GUO ; Jiali FANG ; Guanghui LI ; Luhao LIU ; Yunyi XIONG ; Wei YIN ; Tong YANG ; Junjie MA ; Zheng CHEN
Organ Transplantation 2026;17(2):250-256
Objective To preliminarily investigate the safety and efficacy of donor pancreas needle biopsy in simultaneous pancreas-kidney transplantation. Methods Clinical data of 7 cases undergoing donor pancreas biopsy were collected retrospectively. All cases underwent donor pancreas biopsy before or during simultaneous pancreas-kidney transplantation. Frozen section or paraffin sectioning techniques were used for tissue preparation, and hematoxylin-eosin and Masson staining were performed to histologically evaluate the donor pancreas. The quality of donor pancreas was comprehensively assessed by combining histological findings with the donor's clinical data. Postoperative follow-up data of 5 simultaneous pancreas-kidney transplant recipients were collected to summarize the safety of donor pancreas biopsy and the prognosis of transplant recipients. Results The 7 pancreas donors were aged 28 to 62 years, with a body mass index ranging from 20.76 to 27.68 kg/m2. Liver ultrasound indicated fatty liver in 3 cases, while pancreatic ultrasound did not reveal any significant abnormalities. Among them, biopsy was performed on 2 donors after completion of pancreatic procurement and processing, and the frozen section histology showed moderate acute pancreatitis changes (edema of acinar cells, necrosis and inflammatory cell infiltration). Combined with a serum amylase level elevated more than 3 times the upper limit of normal value, these two donor pancreases were finally discarded. The remaining 5 cases underwent biopsy immediately after pancreatic vascular anastomosis during simultaneous pancreas-kidney transplantation, and histological evaluation was performed on paraffin-embedded sections. No biopsy-related complications (such as bleeding, pancreatic fistula, etc.) occurred after transplantation. One recipient died of severe infection 2 months after transplantation, while the other 4 recipients were followed up for more than 5 years, with well-functioning transplant kidneys and pancreases. Conclusions Donor pancreas biopsy is relatively safe, and the risk of biopsy-related complications after transplantation is controllable. Comprehensive assessment of donor pancreas quality by combining histological evaluation with the donor's clinical indicators is conducive to improving the accuracy of donor pancreas selection and organ utilization.
2.Analysis of Chronic Gouty Arthritis Animal Models Based on Clinical Characteristics of Traditional Chinese and Western Medicine
Yan XIAO ; Siyuan LIN ; Fan YANG ; Qianglong CHEN ; Xiaohua CHEN ; Meiling WANG ; Zhen ZHANG ; Jiali LUO ; Youxin SU ; Jiemei GUO
Chinese Journal of Experimental Traditional Medical Formulae 2026;32(7):84-92
ObjectiveBased on the clinical characteristics of chronic gouty arthritis (CGA) in both traditional Chinese and western medicine, this study aims to systematically evaluate the clinical concordance of existing CGA animal models, providing recommendations for establishing animal models that align with the pathological characteristics of CGA and the manifestations of traditional Chinese medicine syndromes. MethodsBy comprehensively retrieving Chinese and international databases such as China National Knowledge Infrastructure, Wanfang, VIP Chinese Science and Technology Periodical Database (VIP), and PubMed, all relevant literature on CGA animal models was collected. Based on the guidelines, the diagnostic criteria of both traditional Chinese and western medicine were summarized and organized. The evaluation indicators for the CGA model were constructed with reference to existing evaluation modes, and the CGA animal models were analyzed to systematically evaluate the clinical concordance of existing models. ResultsThe current methods used to construct CGA animal models mainly include monosodium urate crystal induction, high-protein diet induction (poultry lack urate oxidase), and high-fat diet combined with urate oxidase inhibitors and joint injection. Based on 11 pieces of included literature, the traditional Chinese and western medicine scoring data of each model were extracted, and the average scoring values of all models were ultimately calculated. The results show that the average clinical concordances of existing CGA animal models in both traditional Chinese and western medicine are 43.33% and 64.44%, respectively. Among them, the model with the highest clinical concordance rate is the one with a high-fat diet combined with potassium oxonate to induce hyperuricemia plus joint injection, achieving 83.33% clinical concordance in western medicine and 60% in traditional Chinese medicine. This model aligns well with the pathogenic characteristics and pathological changes of clinical CGA. ConclusionAlthough current CGA animal models can simulate some pathological characteristics of CGA, they struggle to comprehensively reflect the complex pathological processes of CGA and the characteristics of traditional Chinese medicine syndromes. Therefore, in the future, it is necessary to establish the CGA animal models that incorporate the clinical disease and syndrome characteristics of traditional Chinese and western medicine and formulate the uniform model evaluation criteria, providing more precise tools for CGA mechanism research and the development of traditional Chinese medicine.
3.Practice in Validity Period Management of Disinfectants, Feed, and Bedding in Laboratory Animal Facilities under Good Laboratory Practice Management System
Wenjing MA ; Yanping LIU ; Yifan LI ; Huan GUO ; Lihui XIE ; Longji DU ; Jiali MA ; Hongping WANG ; Jiamin LI
Laboratory Animal and Comparative Medicine 2026;46(4):593-603
ObjectiveTo meet the requirements of Good Laboratory Practice (GLP), Sichuan Institute for Drug Control (Sichuan Testing Center of Medical Devices, Sichuan Institute of Musk Deer Breeding) Safety Evaluation Center (hereinafter referred to as the center) conducts a targeted validation study to address the lack of supporting data for the specified validity periods of disinfectants, feed, and bedding during their use in laboratory animal facilities. The study summarizes practical experience in material management and provides a scientific basis for the standardized management of materials in the facility. MethodsUnder the routine operating conditions of the laboratory animal facility at the center, the disinfection efficacy of four commonly used disinfectants was confirmed using the quantitative suspension kill test, with the disinfectants tested on day 0, day 7, and at 1, 2, and 3 months after preparation and after opening; for laboratory animal feed, nutritional components, chemical contaminants, and microbial indicators were tested 7 days after opening; microbial indicators of laboratory animal corncob bedding were tested after storage for 7 days following opening and sterilization. ResultsUnder the GLP management system of our center, the disinfection efficacy log reduction values of prepared 0.04% sodium hypochlorite solution, 0.1% didecyldimethylammonium bromide solution, and 0.2% benzalkonium bromide solution were all ≥5 on days 0 and 7. The log reduction values of opened 75% ethanol were ≥5 on days 0 and 7 and at 1, 2, and 3 months after opening. All disinfectants were therefore qualified and effective. Compared with the factory inspection data, the nutritional components, chemical contaminants, and microbial indicators of SPF-grade rat and mouse maintenance feed, SPF-grade guinea pig growth and reproduction feed, conventional-grade guinea pig growth and reproduction feed, rabbit maintenance feed, and dog maintenance feed showed a slight overall downward trend but no significant differences 7 days after opening. The microbial indicators of specialized corncob bedding for SPF-grade laboratory animals stored for 7 days after opening and conventional-grade corncob bedding stored for 7 days after sterilization showed no significant fluctuations. All indicators still met the relevant requirements of GB/T 14924.2—2001 Laboratory Animals—Hygienic Standard for Formula Feeds and GB 14924.3—2010 Laboratory Animals—Nutrients for Formula Feeds. ConclusionBased on practical experience in managing the center's GLP laboratory animal facility and validation of core quality indicators, the specified validity periods of disinfectants, feed, and bedding meet the quality requirements, providing a practical reference for the standardized management of laboratory animal facilities.
4.Exploring Pathogenesis and Treatment of Primary Osteoporosis from Theory of Qi Deficiency and Stagnation and Mitochondrial Autophagy
Jiali ZHANG ; Yubin ZHANG ; Ruoying SONG ; Jianqiang LI ; Feng LI ; Jiayi GUO
Chinese Journal of Experimental Traditional Medical Formulae 2026;32(20):230-241
Primary osteoporosis (POP) is a metabolic bone disease characterized by reduced bone mass, degenerated bone microstructure, and increased bone fragility. Its pathogenesis involves the interaction of multiple factors such as genetics, aging, endocrine, and environment, which remain incompletely elucidated. Mitochondrial dysfunction can lead to insufficient adenosine triphosphate (ATP) production and abnormal accumulation of reactive oxygen species (ROS), activating oxidative stress and inflammation pathways, thereby inhibiting osteoblast differentiation and promoting osteoclast activation, exacerbating the negative bone metabolism balance in POP. Mitochondrial autophagy, as the core mechanism of mitochondrial quality control, selectively identifies and clears damaged mitochondria to effectively reduce ROS accumulation and energy metabolism disorders, thus maintaining the balance between osteoblast and osteoclast differentiation. It plays a critical role in maintaining bone homeostasis and the prevention and treatment of POP. The traditional Chinese medicine (TCM) theory of Qi transformation shares similarities with the functions of mitochondria in energy generation and substance conversion. The pathological state of Qi deficiency and stagnation may be associated with mitochondrial autophagy dysfunction, and the pathogenic characteristics of combined phlegm and stasis align with the metabolic waste accumulation induced by obstructed autophagy flow. This article explores the correlation of the theory of Qi deficiency and stagnation with mitochondrial autophagy and elucidates its potential role in the pathogenesis of POP. Additionally, considering the pathogenesis features of POP, which involve deficiency causing stagnation and a mixture of deficiency and excess, this article proposes a novel therapeutic approach: tonifying Qi to support the body and unblocking collaterals to resolve stagnation from the perspective of mitochondrial autophagy. This article aims to provide theoretical support and research insights for further exploration of TCM in the prevention and treatment of POP.
5.Exploring Pathogenesis and Treatment of Primary Osteoporosis from Theory of Qi Deficiency and Stagnation and Mitochondrial Autophagy
Jiali ZHANG ; Yubin ZHANG ; Ruoying SONG ; Jianqiang LI ; Feng LI ; Jiayi GUO
Chinese Journal of Experimental Traditional Medical Formulae 2026;32(20):230-241
Primary osteoporosis (POP) is a metabolic bone disease characterized by reduced bone mass, degenerated bone microstructure, and increased bone fragility. Its pathogenesis involves the interaction of multiple factors such as genetics, aging, endocrine, and environment, which remain incompletely elucidated. Mitochondrial dysfunction can lead to insufficient adenosine triphosphate (ATP) production and abnormal accumulation of reactive oxygen species (ROS), activating oxidative stress and inflammation pathways, thereby inhibiting osteoblast differentiation and promoting osteoclast activation, exacerbating the negative bone metabolism balance in POP. Mitochondrial autophagy, as the core mechanism of mitochondrial quality control, selectively identifies and clears damaged mitochondria to effectively reduce ROS accumulation and energy metabolism disorders, thus maintaining the balance between osteoblast and osteoclast differentiation. It plays a critical role in maintaining bone homeostasis and the prevention and treatment of POP. The traditional Chinese medicine (TCM) theory of Qi transformation shares similarities with the functions of mitochondria in energy generation and substance conversion. The pathological state of Qi deficiency and stagnation may be associated with mitochondrial autophagy dysfunction, and the pathogenic characteristics of combined phlegm and stasis align with the metabolic waste accumulation induced by obstructed autophagy flow. This article explores the correlation of the theory of Qi deficiency and stagnation with mitochondrial autophagy and elucidates its potential role in the pathogenesis of POP. Additionally, considering the pathogenesis features of POP, which involve deficiency causing stagnation and a mixture of deficiency and excess, this article proposes a novel therapeutic approach: tonifying Qi to support the body and unblocking collaterals to resolve stagnation from the perspective of mitochondrial autophagy. This article aims to provide theoretical support and research insights for further exploration of TCM in the prevention and treatment of POP.
6.Development of a questionnaire for residents to evaluate the quality of general practice teaching clinics
Jiali WANG ; Congling ZHANG ; Jie LIU ; Guifen ZHANG ; Ruoxia ZHANG ; Xinmei ZHOU ; Weifang MO ; Lingyan WU ; Yuling TONG ; Yi GUO ; Zhijie XU
Chinese Journal of Medical Education Research 2025;24(11):1505-1511
Objective:To develop a scientific and practical questionnaire for general practice residents, and to conduct multidimensional and comprehensive evaluation of the quality of general practice teaching clinics.Methods:A preliminary draft of the questionnaire items was formulated based on a literature review and in-depth interviews. The Delphi method was employed to conduct two rounds of consultation with 14 experts. Following revisions, a convenience sampling method was used to invite general practice residents from three standardized residency training bases to test the reliability and validity of the questionnaire.Results:The questionnaire consisted of 23 items, covering the three dimensions of preparation, implementation process, and comprehensive evaluation of the teaching clinics. The response rates for the two rounds of the expert consultation were both 100.00%, with expert authority coefficients of 0.89 and 0.90, respectively. The overall Cronbach's α coefficient of the questionnaire was 0.93, and the correlation coefficients between each item score and the total score were all >0.30. Structural validity analysis revealed that three common factors were extracted from the questionnaire, with a cumulative variance contribution rate of 77.89%. Conclusions:The General Practice Teaching Clinic Quality Evaluation Questionnaire for Residents developed in this study demonstrates high reliability and validity. The questionnaire provides a scientific basis for the standardized assessment of teaching quality in general practice clinics. By incorporating resident feedback on the teaching process, the questionnaire promotes the development of a teaching clinic quality improvement mechanism focused on residents and plays a significant role in enhancing the teaching capabilities of supervising physicians in clinics.
7.Self-assembled drug-loaded nanoprobes for pyroptosis sensitization and chemical exchange saturation transfer imaging in breast cancer
Jiali DENG ; Jiajing GUO ; Jingyi WANG ; Xinyi DING ; Yi ZHU ; Zhongling WANG
Journal of Shanghai Jiaotong University(Medical Science) 2025;45(3):271-281
Objective·To prepare self-assembled drug-loaded nanoprobes with activatable chemical exchange saturation transfer(CEST)imaging capability,and evaluate their imaging performance and therapeutic potential for photodynamic-sensitized pyroptosis in breast cancer in vivo and in vitro.Methods·GC nanoprobes co-loaded with gemcitabine(Gem)and chlorin e6(Ce6)were constructed by using a self-assembly strategy.The physicochemical properties of the GC nanoprobes were characterized by scanning electron microscopy(SEM)and dynamic light scattering(DLS).The pH-/time-dependent CEST activation and drug release profiles were investigated.The 2',7'-dichlorodihydrofluorescein diacetate(DCFH-DA)probe was used to detect the generation of reactive oxygen species(ROS),and enzyme-linked immunosorbent assay(ELISA)was used to detect the release of inflammatory factors such as interleukin-1β(IL-1β)and IL-18 in mouse breast cancer 4T1 cells after treatment with GC nanoprobes with synergistic laser irradiation.Immunofluorescence was performed to detect immunogenic cell death(ICD)markers,including calreticulin(CRT)and high mobility group box 1 protein(HMGB1).The 4T1 breast cancer mouse models were established to validate tumor-specific CEST activation and evaluate anti-tumor efficacy by measuring tumor volume and detecting inflammatory factors and ICD markers.Results·SEM and DLS confirmed the uniform spherical morphology of the GC nanoprobes.The CEST imaging results showed that the nanoprobes had excellent pH-concentration and time-dependent activation imaging effects both in the simulated acidic microenvironment and at the cellular level in vitro.The drug release from this drug-loaded nanoprobe was 80%at pH 5.0,which was significantly higher than at pH 7.4(P=0.003).DCFH-DA fluorescence staining demonstrated that GC-mediated photodynamic therapy induced a significant generation of ROS.Analysis of pyroptosis-related factors revealed a marked increase in the release levels of IL-1β and IL-18(both P<0.05),along with elevated fluorescence expression of CRT and HMGB1.The in vivo CEST imaging results showed that the CEST signal at the tumor site was significantly enhanced,peaking at 4 h with tail vein injection of GC.The GC nanoprobes with synergistic laser irradiation group showed markedly elevated inflammatory factors(IL-1β,IL-18),changed ICD biomarkers(HMGB1 and CRT),and significant tumor suppression,compared to the PBS control group(all P<0.05).Conclusion·The GC nanoprobes enables specific CEST imaging-guided photodynamic therapy,effectively inducing pyroptosis and precise ablation of breast cancer.
8.Experimental study on novel pH-responsive manganese-based nanoprobes for ferroptosis and magnetic resonance imaging in breast cancer
Jingyi WANG ; Jiali DENG ; Yi ZHU ; Xinyi DING ; Jiajing GUO ; Zhongling WANG
Journal of Shanghai Jiaotong University(Medical Science) 2025;45(9):1183-1193
Objective·To construct a pH-responsive manganese-based nanoprobe and explore the therapeutic efficacy of chemotherapy/ferroptosis synergistic treatment in breast cancer and the effect of pH-responsive magnetic resonance-activated imaging.Methods·BSA-MnO2@CPT(BMC)nanoprobes were prepared by biomineralization,and their physicochemical properties were characterized by transmission electron microscope(TEM)and dynamic light scattering.The magnetic resonance imaging(MRI)was used to evaluate the pH-responsive MRI T1 activation and time-dependent activation efficacy at the cellular level,with quantitative analysis of MRI T1 signal intensity.The reactive oxygen species(ROS)generation and glutathione(GSH)depletion by BMC nanoprobes were respectively detected by methylene blue(MB)and DTNB in vitro.The synergistic efficacy of chemotherapy and ferroptosis mediated by the nanoprobes in 4T1 breast cancer cells was evaluated using the Thiazolyl Blue Tetrazolium Bromide(MTT)assay.After co-incubation 4T1 cells with BMC,intracellular ROS levels were determined through the staining of ROS fluorescence indicator 2',7'-dichlorodihydrofluorescein diacetate(DCFH-DA)and the level of lipid peroxide(LPO)expression was detected by using BODIPY581/591 C11 probe.A subcutaneous xenograft tumor model of 4T1 breast cancer was established in mice,with four experimental groups:Control group(PBS group),CPT group,BSA-MnO2(BM)group,and BMC group.The pH-responsive T1 activation effect of the BMC nanoprobes was dynamically monitored in vivo,while the ferroptosis-based antitumor efficacy was evaluated by measuring tumor volume and ferroptosis biomarkers(LPO and ROS).Results·TEM revealed that the prepared BMC nanoprobes exhibited a spherical morphology with an average diameter of approximately 150 nm.The MRI results demonstrated that the nanoprobes were pH-activable,exhibiting progressively enhanced T1 signal intensity under acidic conditions,and displaying pH-dependent r1 relaxivity enhancement.These findings validated their dual pH/time-responsive activation efficacy at the cellular level.In vitro solution-level MB and DTNB assays demonstrated that the BMC nanoprobes effectively enhanced the generation of ROS and the consumption of GSH.Fluorescence staining with DCFH-DA and BODIPY581/591 C11 demonstrated that the combination of ferroptosis effect and chemotherapy significantly enhanced intracellular generation of ROS and LPO accumulation.The MTT assay demonstrated that the survival rate of tumor cells significantly decreased to 17%(P=0.003).In vivo MRI demonstrated that the T1 signal was significantly enhanced and reached its peak at 4 h after tail vein injection of the BMC nanoprobes.Furthermore,in vivo antitumor therapy showed that the BMC group exhibited upregulated levels of LPO and ROS in tumor tissues,accompanied by marked tumor suppression(P=0.009).Conclusion·The pH-responsive theranostic BMC nanoprobes enhances antitumor efficacy via the synergistic interaction of chemotherapy and ferroptosis,while enabling tumor microenvironment-activated MRI.
9.Clinical efficacy analysis of modified splenic arteriovenous shunt surgery at the distal end of the pancreatic tail in combined pancreas-kidney transplantation
Wei YIN ; Meng LI ; Jiali FANG ; Guanghui LI ; Junjie MA ; Yuhe GUO ; Weiting ZHANG ; Lu XU ; Luhao LIU ; Zheng CHEN
Chinese Journal of Organ Transplantation 2025;46(3):219-225
Objective:To evaluate the efficacy of modified splenic arteriovenous shunt surgery at the distal pancreatic tail in combined pancreas-kidney transplantation.Methods:A retrospective analysis was conducted on 24 recipients who underwent combined pancreas-kidney transplantation with the modified splenic arteriovenous shunt at the pancreatic tail from November 2023 to October 2024 (shunt group) and 231 recipients who received conventional splenic artery and vein ligation since 2016 (ligation group). The incidence of perioperative thrombosis and severe adverse events was compared between the two groups using the chi-square test or Fisher's exact test. Independent sample t-tests were performed to assess postoperative pancreatic and renal function recovery as well as blood perfusion in 15 recipients from the shunt group and 20 from the ligation group who underwent CT perfusion imaging (CTP).Results:The incidence of perioperative splenic arteriovenous thrombosis was lower in the shunt group (0) compared to the ligation group (4.76%, 11/231), though the difference was not statistically significant ( P=0.606). One month postoperatively, the shunt group demonstrated significantly lower serum amylase levels than the ligation group (99.61±19.62 vs. 148.20±70.67 U/L, P=0.018). However, at the time of CTP examination, serum lipase (67.87±32.35 vs. 45.11±17.94 U/L, P=0.014) and creatinine levels (131.79±26.41 vs. 112.1±24.98 μmol/L, P=0.034) were significantly higher in the shunt group. Urea nitrogen levels were also significantly higher in the shunt group both one month postoperatively (11.24±4.64 vs. 8.51±3.01 mmol/L, P=0.043) and at the CTP examination (10.41±1.78 vs. 6.87±1.91 mmol/L, P=0.001). Regarding pancreatic perfusion, blood volume in both the pancreatic head (15.99 ± 3.51 vs. 20.67 ± 5.47 ml/100 g, P = 0.024) and tail (17.19±4.24 vs. 27.40±19.80 ml/100 g, P=0.039) was significantly lower in the shunt group. After one minute of splenic artery perfusion, the shunt group exhibited significantly higher splenic artery blood flow (755.85±101.50 vs. 574.00 ± 142.06 ml·min -1· (100 g) -1, P<0.001) and blood volume (58.90 ±19.93 vs. 23.21±17.02 ml/100 g, P=0.007) compared to the ligation group. These differences persisted after two minutes of perfusion (blood flow: 793.83±68.57 vs. 503.78 ± 130.80 ml·min -1· (100 g) -1, P<0.001; blood volume: 64.22±15.74 vs. 34.32±20.39 ml/100 g, P=0.002). For the transplanted kidney, the shunt group had significantly lower blood flow (113.10±28.55 vs. 232.76±113.37 ml·min -1· (100 g) -1, P<0.001), blood volume (28.95±10.79 vs. 38.36±12.38 ml/100 g, P=0.047), and capillary surface permeability (PS) (26.49±16.57 vs. 43.02±20.37, P = 0.042) in the upper pole. Similar reductions in blood flow, blood volume, and PS were observed in the middle dorsal region ( P=0.018, 0.021, and 0.048, respectively) and lower pole ( P<0.001, P=0.048, and P=0.012, respectively). Conclusion:The modified splenic arteriovenous shunt at the pancreatic tail appears to be a safe and effective approach to reducing the risk of pancreatic graft thrombosis. This technique facilitates effective diversion of pancreatic parenchymal blood flow into the splenic vein, alleviating hyperperfusion of the transplanted pancreas. While renal blood perfusion was reduced postoperatively, it did not adversely affect renal function.
10.Biomechanical Mechanism of Rocking-Chair Arch wire in En-Masse Retraction of Maxillary Anterior Teeth
Jiaying HU ; Jiali LIU ; Zhen LIN ; Jinquan GUO ; Xie SHI ; Jiehua SU
Journal of Medical Biomechanics 2025;40(4):858-865
Objective To establish a simplified simulation method of rocking-chair archwire(RCA),explore the biomechanical effect of RCA during anterior teeth retraction with sliding mechanics,and provide guidance for clinical treatment.Methods A standard 0.019 in×0.025 in(0.483 mm×0.635 mm)labial archwire was imported into ANSYS software and preloaded spring was used to simulate RCA at different angles to achieve parameterized modeling.A three-dimensional(3D)finite element model with labial straight wire appliance,teeth,periodontium and maxillary bone was established to analyze the displacement and force of anterior/posterior teeth under 1.5 N intra-arch traction combined with RCA at different angles.Results Preloading forces of 1.5,3,4.5,and 6 N in spring induced angles of approximately 5°,10°,15°,and 20° for RCA,demonstrating the flexibility and convenience of the parameterized modeling method.During intra-arch traction with increased angle of RCA,lingual crown displacement of the middle incisor gradually decreased,while the lateral incisor and canine showed decreased crown tipping and increased lingual root displacement;when the RCA angle was 20°,the lateral incisor and canine achieved almost bodily retraction.Meanwhile,premolars showed an extrusion tendency,while molars demonstrated distal crown tipping and intrusion tendency.As the RCA angle increased from 0° to 20°,intrusive force on the anterior teeth increased,and the moment-force ratio(M/F)at bracket level increased from 0 to near 9 mm.Conclusions RCA can effectively control the moving pattern of the maxillary anterior teeth and prevent their over-erection and extrusion during retraction with sliding mechanics.During intra-arch traction with rigid stainless steel archwire,theoretically RCA of 20° has sufficient torque control on the anterior teeth to achieve their en-masse retraction.

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