1.Comparative study of different treatment methods for peroneus longus tendon stump in anterior cruciate ligament reconstruction.
Peng WANG ; Zhiwei LIU ; Zhonghua SHI ; Fan ZHAO ; Jiawen WANG ; Huan LI
Chinese Journal of Reparative and Reconstructive Surgery 2025;39(12):1526-1531
OBJECTIVE:
To compare the impact of different peroneus longus tendon (PLT) stump management techniques on ankle function following arthroscopic anterior cruciate ligament (ACL) reconstruction with autologous PLT grafts.
METHODS:
A retrospective analysis was conducted on 60 patients with ACL rupture who met the inclusion criteria between August 2020 and July 2024. All patients underwent arthroscopic ACL reconstruction using the autologous PLT grafts. Patients were assigned to group A [PLT stump sutured to peroneus brevis tendon (PBT), n=30] or group B (no stump intervention, n=30). The two groups showed no significant difference ( P>0.05) in baseline data, including gender, age, body mass index, injury mechanism, affected side, preoperative American Orthopaedic Foot and Ankle Society (AOFAS) score, ankle muscle strength, ankle range of motion, and arch-related angles. Postoperative outcomes were assessed using the AOFAS score, ankle muscle strength (eversion and first-ray plantar flexion), arch-related angles (medial/lateral longitudinal and anterior/posterior arch), ankle range of motion (eversion, inversion, dorsiflexion, plantarflexion), and limb symmetry index (LSI). Change values in muscle strength, arch-related angles, and range of motion from preoperative to 12 months postoperatively were calculated for intergroup comparison.
RESULTS:
Groups A and B had comparable PLT graft lengths and diameters ( P>0.05). All patients were followed up 13-16 months (mean, 14.5 months). Postoperative complications included 1 case of incision infection, 1 case of deep vein thrombosis, and 1 case of knee stiffness in group A, 1 case of knee stiffness in group B. There was no significant difference in the overall complication incidences between groups ( P>0.05). No significant difference was found in the AOFAS scores between different time points and between groups ( P>0.05). At 12 months after operation, neither group showed significant changes from preoperative baseline in ankle strength, range of motion, or arch-related angles, and there was no significant difference in these change values between groups ( P>0.05). There was no significant difference in LSI between the two groups at 6 or 12 months postoperatively ( P>0.05).
CONCLUSION
Both suturing and leaving the PLT stump untreated during arthroscopic ACL reconstruction provided comparable ankle outcomes and well-preserved foot and ankle function.
Humans
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Anterior Cruciate Ligament Reconstruction/methods*
;
Male
;
Retrospective Studies
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Female
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Adult
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Anterior Cruciate Ligament Injuries/surgery*
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Tendons/transplantation*
;
Range of Motion, Articular
;
Arthroscopy/methods*
;
Young Adult
;
Treatment Outcome
;
Muscle Strength
;
Transplantation, Autologous
;
Ankle Joint/surgery*
;
Middle Aged
;
Adolescent
2.Research progress in radiation-induced rectal injury
Jiawen GUO ; Ye ZHANG ; Jinbo YUE ; Wencheng ZHANG ; Qifeng WANG ; Pei YANG ; Hongyun SHI
Chinese Journal of Radiation Oncology 2025;34(9):882-889
Radiation-induced rectal injury (RRI) refers to inflammatory intestinal complications of patients with pelvic cavity, abdominal cavity and retroperitoneal tumor during or after radiotherapy, presenting symptoms such as diarrhea, abdominal pain, anal distension, bloody stool, etc. In severe cases, rectovaginal fistula, intestinal obstruction, canceration can occur, adversely affecting the quality of life of patients. The clinical factors of RRI involve total radiotherapy dose, tumor volume, radiotherapy mode and patient-related risk factors. The diagnosis mainly depends on imaging examinations (such as CT, MRI and ultrasound), endoscopy and laboratory examination. The mechanism of RRI is related to intestinal epithelial cell destruction, stem cell injury, microvascular changes and microbial flora imbalance. At present, there is no gold standard for RRI treatment, and the main measures include surgical treatment, internal medicine treatment, hyperbaric oxygen therapy and fecal microbiota transplantation, etc. In this article, the latest progress in the pathogenesis, diagnosis and treatment of RRI was reviewed.
3.Clinicopathological and molecular genetic heterogeneity of diffuse gliomas with the features of polymorphous low-grade neuroepithelial tumor of the young
Xiaoli SU ; Jiawen WU ; Pingling WANG ; Liwen HU ; Yupeng CHEN ; Caihong REN ; Fangling SONG ; Hangrui LIN ; Sheng ZHANG ; Xingfu WANG
Chinese Journal of Pathology 2025;54(11):1163-1171
Objective:To investigate the clinicopathological and molecular genetic characteristics of diffuse gliomas with the features of polymorphous low-grade neuroepithelial tumor of the young (PLNTY) and their prognostic values.Methods:A retrospective analysis was performed on 14 cases of diffuse gliomas with PLNTY features diagnosed at the First Affiliated Hospital of Fujian Medical University, Fuzhou, China from June 2020 to August 2024. Their clinicopathological characteristics were examined, and their molecular genetic and epigenetic features were assessed using next-generation sequencing (NGS) and methylation analysis. Factors influencing prognosis were also analyzed.Results:Among the 14 patients, there were 8 males and 6 females, aged 3-62 years, median 29 (9, 50) years. All cases were initially diagnosed as low-grade diffuse gliomas histologically but exhibited the histological and immunohistochemical features of PLNTY. At the molecular level, all cases showed molecular abnormalities involving the mitogen-activated protein kinase pathway, including 5 cases with FGFR3-TACC3 (F3T3) fusion, 3 cases with FGFR2 fusion, 5 cases with BRAF V600E mutation, and 1 case with FGFR1 mutation. Among them, TERT promoter mutations were frequently observed in tumors with F3T3 fusion (5/5), while NCOR2 in-frame insertion mutations were prominent in tumors with non-F3T3 fusions. Clinical follow-up showed recurrence in 3 cases, all of which had F3T3 fusion and concurrent TERT promoter mutations. Prognostic analysis confirmed that F3T3 fusion with concurrent TERT promoter mutation was associated with poor prognosis.Conclusions:Diffuse gliomas with PLNTY features exhibit heterogeneity in clinicopathology and molecular genetics, with FGFR3/FGFR2 fusions and BRAF/FGFR1 mutations as the most common molecular alteration. They often have concurrent F3T3 fusion and TERT promoter mutations, which are related to poor prognosis. The possibility of molecular glioblastoma should be considered for these tumors. It is thus recommended to perform genetic testing on diffuse gliomas with PLNTY features in order to facilitate integrated diagnosis and provide molecular evidence for accurate evaluation of prognoses.
4.Application of photodynamic therapy with different wavelength light excitation in cancer treatment
Yuejie ZHOU ; Jiawen ZHAO ; Jiafu LIANG ; Yun GONG ; Jingwen WANG ; Zhiping LIU ; Xiaofei LIU
Journal of Xi'an Jiaotong University(Medical Sciences) 2025;46(2):353-362
Photodynamic therapy(PDT)is a precise targeted therapy that selectively treats certain benign diseases and malignant tumors by combining therapeutic light sources,photosensitizers,and oxygen molecules.The wavelength range of the light source,as a key factor in inducing PDT,has a decisive impact on the triggering and therapeutic effect of the treatment.However,there is a lack of relevant reviews on the selection of light sources for photodynamic therapy.This article reviews the PDT-related applications of commonly used light sources with different wavelength ranges of excitation,such as visible light,near-infrared,and X-ray,including the excitation characteristics of this band of light,as well as the multi-therapy combination and multi-range breakthroughs of PDT cancer treatment under the excitation of this band of light.The aim is to provide feasible directions for the development of photodynamic therapy bands and subsequent applications.
5.Mediating effect of psychological flexibility between pain self-efficacy and kinesiophobia on patients with lumbar disc herniation
Yanxin XU ; Lishan HUANG ; Jing CHEN ; Lin WANG ; Xuan REN ; Jiawen HUO ; Rui LI ; Aoxiang LUO
Modern Clinical Nursing 2025;24(2):48-54
Objective To investigate the mediating effect of psychological flexibility on the relationship between pain self-efficacy and kinesiophobia in patients with lumbar disc herniation(LDH),so as to provide references for relief from kinesiophobia of the patients.Methods Convenience sampling was used to select 256 patients with LDH as the research subjects from the Outpatient Department of Spinal Orthopaedics of a Grade IIIA hospital in Guangdong Province between May and December 2023.The subjects were surveyed with a general information questionnaire,the kinesiophobia assessment scale,psychological flexibility inventory for pain patients,and chronic pain self-efficacy scale.The mediation effect of psychological flexibility on pain self-efficacy and kinesiophobia was analysed using SPSS 26.0 and the PROCESS 3.5 macro.Results The scores for kinesiophobia,psychological flexibility and pain self-efficacy among the LDH patients were 31.66±4.73,55.26±11.06 and 68.14±17.48,respectively.Kinesiophobia was positively correlated with the psychological flexibility(r=0.545,P<0.001)and negatively correlated with the pain self-efficacy(r=-0.599,P<0.001).The psychological flexibility was negatively correlated with the pain self-efficacy(r=-0.510,P<0.001).Psychological flexibility partially mediated the relationship between pain self-efficacy and kinesiophobia,with a mediating effect of-0.045,accounting for 27.78%of the total effect.Conclusion The patients who have LDH and under conservative treatment exhibit a high level of kinesiophobia and with a moderate levels of pain self-efficacy and psychological flexibility.The medical staff can improve the self-efficacy and psychological flexibility of patients,so as to reduce kinesiophobia level and its incidence.
6.The impact of Qingfeihuayutongfu prescription on respiratory mechanics,inflammatory markers,and immune function in mechanically ventilated patients with sepsis-associated acute respiratory distress syndrome
Lu CHENG ; Jiawen YUAN ; Qinyun LU ; Yuhao HANG ; Jun LU ; Dexiang WANG
Chinese Journal of Integrated Traditional and Western Medicine in Intensive and Critical Care 2025;32(2):149-154
Objective To observe the effects of the traditional Chinese medicine Qingfeihuayutongfu prescription on oxygenation index,respiratory mechanics,inflammatory markers,and immune function in mechanically ventilated patients with sepsis-associated acute respiratory distress syndrome(ARDS).Methods A prospective randomized controlled trial was conducted.Sixty-eight patients with sepsis-associated ARDS,who met the TCM syndrome pattern of lung-heat transferring to intestines syndrome,admitted to the department of intensive care unit(ICU)of the Affiliated Hospital of Nanjing University of Chinese Medicine between January 2023 and January 2024,were enrolled as study subjects.Patients were randomly divided into an experimental group and a control group using a random number table,with 34 patients in each group.Four patients dropped out from each group,resulting in 30 patients being analyzed in each group.Both groups received conventional Western medical treatment after admission.The experimental group additionally received Qingfeihuayutongfu prescription[composition:Scutellaria baicalensis 10 g,Mori Cortex 10 g,Descurainiae Semen 15 g,Trichosanthis Fructus 10 g,Lumbricus 10 g,Persicae Semen 10 g,Salviae Miltiorrhizae Radix 10 g,Curcumae Rhizoma 6 g,Rheum palmatum 3 g(decocted later),Aurantii Fructus Immaturus 10 g,Magnoliae Officinalis Cortex 10 g,Glycyrrhizae Radix praeparata 3 g].The decoction was concentrated to 100 mL per bag.One dose was administered daily,divided into 2 nasogastric feedings.The control group received an equivalent volume of warm water twice daily via nasogastric tube in addition to conventional Western treatment.Treatment continued for 7 days in both groups.Differences in oxygenation index,respiratory mechanics parameters,inflammatory cytokines,and immune cell levels before and after treatment were compared between the two groups.Results Prior to treatment,no statistically significant differences were observed between the two groups in oxygenation index,respiratory mechanics parameters,levels of inflammatory cytokines or immune cell counts.Following treatment,both groups exhibited a significant increase in oxygenation index and natural killer cell(NK cell),alongside significant decreases in plateau pressure(Pplat),driving pressure(ΔP),hypersensitive C-reactive protein(hs-CRP),procalcitonin(PCT),interleukins(IL-6,IL-8,IL-1β),tumour necrosis factor-α(TNF-α),and CD4+/CD8+ratio compared to baseline.Post-treatment comparison between groups revealed that the experimental group had a significantly higher oxygenation index and NK cell than the control group[oxygenation index(mmHg,1 mmHg≈0.133 kPa):331.32±90.89 vs.238.64±83.26,NK cell:0.20(0.12,0.25)vs.0.10(0.08,0.19),both P<0.05].Conversely,the experimental group demonstrated significantly lower values than the control group for Pplat,ΔP,hs-CRP,PCT,IL-6,IL-8,TNF-α,CD4+/CD8+[Pplat(cmH2O,1 cmH2O≈0.098 kPa):16(15,19)vs.22(19,24),ΔP(cmH2O):11±2 vs.14±3,hs-CRP(mg/L):21.32(11.63,31.84)vs.41.36(17.41,89.02),PCT(μg/L):0.13(0.08,0.21)vs.0.45(0.14,1.35),IL-6(ng/L):16.25(10.72,49.96)vs.66.70(25.82,195.64),IL-8(ng/L):5.48(0.84,12.60)vs.26.23(23.10,50.16),TNF-α(ng/L):0.77(0.72,1.20)vs.1.10(0.92,1.48),CD4+/CD8+:1.76(1.43,2.00)vs.2.12(1.77,4.03),all P<0.05].Conclusion The Qingfeihuayutongfu prescription can effectively improves the oxygenation index,reduces Pplat and ΔP,mitigates inflammation,and modulates immune function in mechanically ventilated patients with sepsis-associated ARDS.
7.A two-sample Mendelian randomization study of the association between type 2 diabetes mellitus and papillary thyroid cancer
Jiawen WANG ; Qiuyu LIN ; Nan JIANG ; Shuangyan ZHAO ; Yuxin WANG ; Ying GUO ; Chenghe LIN
Chinese Journal of Nuclear Medicine and Molecular Imaging 2025;45(3):164-168
Objective:To investigate the causal relationship between type 2 diabetes mellitus (T2DM), type 1 diabetes mellitus (T1DM), body mass index (BMI) and papillary thyroid cancer using Mendelian randomization(MR) study.Methods:Publicly available genome-wide association studies (GWAS) were used as the data source to screen single nucleotide polymorphisms significantly associated with exposure factors (instrumental variables), and the inverse variance weighting (IVW), weighted median, MR-Egger analysis, simple mode, and weighted mode of two-sample MR were used to assess the causal association between T2DM, T1DM, BMI and papillary thyroid cancer. The reliability and stability of the results were assessed by heterogeneity analysis, multiple validity analysis and sensitivity analysis.Results:A total of 118 strong instrumental variables for T2DM, 76 for T1DM, and 486 for BMI were screened respectively to conduct two-sample MR analysis. Among the 5 MR analysis methods, the results of the IVW method showed that T2DM was significantly associated with papillary thyroid cancer (odds ratio ( OR)=1.147, 95% CI: 1.026-1.282; P=0.016), and the genetic effect values ( β values) of the other 4 analysis methods and IVW method were in the same direction; the results of heterogeneity analysis, multiplicity analysis and sensitivity analysis showed all P>0.05. T1DM (IVW method: OR=1.000, 95% CI: 0.952-1.051; P=0.994) and papillary thyroid cancer, BMI (IVW method: OR=1.214, 95% CI: 0.923-1.598; P=0.166) and papillary thyroid cancer were not clearly causally related. Conclusions:There is a causal association between T2DM and papillary thyroid cancer, and T2DM increases the risk of papillary thyroid cancer. There is no clear causal association between T1DM, BMI and papillary thyroid cancer.
8.Systematic review of machine learning models for predicting functional recovery and prognosis in stroke
Jiaru WANG ; Ying ZHANG ; Yong YANG ; Wen QI ; Huaye XIAO ; Qiuping MA ; Lianzhao YANG ; Ziwei LUO ; Yaqing HE ; Jiangyin ZHANG ; Jiawen WEI ; Yuan MENG ; Silian TAN
Chinese Journal of Tissue Engineering Research 2025;29(29):6317-6325
OBJECTIVE:Nowadays,machine learning algorithms are gradually being applied to predict stroke and cardiovascular disease.Compared with traditional regression models,machine learning can learn from data to achieve high prediction accuracy by exploring the flexible relationship between a large number of predictive features and outcome variables,providing a new method for the formulation of individualized treatment and rehabilitation programs.This study aims to systematically evaluate stroke functional recovery and prognosis prediction models based on machine learning,comprehensively assessing their predictive performance and clinical application potential to provide references for the development,application,and promotion of related predictive models.METHODS:This review was conducted following the PRISMA(Preferred Reporting Items for Systematic Reviews and Meta-Analyses)guidelines.Relevant literature on stroke prognosis prediction using machine learning methods was selected by searching PubMed,EMbase,Web of Science Core Collection,CNKI,WanFang,and the China Biomedical Literature Database,with the search period from January 1,2014,to July 1,2024.Two researchers independently screened the literature and extracted data based on inclusion and exclusion criteria,using the Prediction model Risk Of Bias ASsessment Tool(PROBAST)to assess model quality.RESULTS:(1)A total of 3 126 articles were obtained in the preliminary search.After screening and exclusion,18 articles were finally included.150 prediction models were constructed using 13 machine learning methods.The three most frequently used methods are Logistic Regression,Random Forest,and Extreme Gradient Boosting(XGBoost).Only one study was externally validated.Eight studies reported how the missing data were handled.(2)In terms of outcome indicators,8 studies used the combination of clinical data and imaging data to build models,9 studies only used clinical data to build models,and 1 study only used imaging data to build models.(3)Each of the 18 studies gave the most important characteristics of the study,with the most mentioned being the National Institute of Health Stroke Scale and age.All studies reported area under curve values ranging from 0.74 to 0.96,with the highest area under curve being 0.96.The overall risk of bias in all models was high.The high risk of bias in the field of model analysis was the main reason for the high risk of overall bias in all models.(4)The results of meta-analysis showed that age and National Institute of Health Stroke Scale score had significant influence on stroke prognosis,with age[MD=8.49,95%CI(6.24,10.75),P<0.01]and National Institute of Health Stroke Scale score[MD=4.78,95%CI(2.56,7.00),P<0.01].CONCLUSION:This study systematically evaluated the predictive model of functional recovery and prognosis of stroke based on machine learning,and all the models have good predictive potential.However,future studies should increase the sample size of the included model,adopt prospective studies,and add external validation of the model to improve the stability and prediction accuracy of the model,control the risk of bias,and contribute to the validation and promotion of the model in practical clinical applications.At the same time,the interpolation of missing values is more transparent and accurate.Although existing machine learning models show good predictive performance,it is also important to focus on the functionality and usability of the model,and the inclusion of features will reduce ease of use.We should develop easy to use model interfaces and user-friendly clinical tools to enable medical staff to better apply the model for clinical decision.
9.Analysis of clinical features and risk factors for severe acute pancreatitis complicated with biliary system diseases
Qiyuan LI ; Yan LUO ; Hua CHEN ; Rui KONG ; Yongwei WANG ; Guanqun LI ; Yiqin SONG ; Xin ZHENG ; Jiajun LI ; Jiawen WU ; Dongxue JU ; Bei SUN
Chinese Journal of Surgery 2025;63(8):712-719
Objective:To explore the clinical characteristics of biliary system diseases complicated by severe acute pancreatitis(SAP) and the risk factors.Methods:This is a retrospective cohort study. A retrospective analysis was conducted on the clinical data of 159 SAP patients admitted to the Department of Pancreatic and Biliary Surgery,the First Affiliated Hospital of Harbin Medical University from January 2019 to October 2024. There were 105 male cases, 54 female cases;aged (42.3±10.8)years (range:20 to 71 years). Grouping was performed according to the presence or absence of concurrent acute acalculous cholecystitis (AAC) and biliary stricture. There were 58 cases in the AAC group,including 40 males and 18 females;aged (43.8±10.6) years (range:28 to 71 years);101 cases in the non-AAC group,including 64 males and 37 females;aged (41.5±10.8) years (range:20 to 64 years);there were statistically significant differences between the two groups in terms of admission total bilirubin,Balthazar-CTSI score,fasting time,and the proportions of concurrent shock and sepsis (all P<0.05);the time from onset of SAP to diagnosis of AAC( M (IQR)) was 10.5 (13.3) days (range: 3 to 34 days). There were 15 cases in the biliary stricture group,including 13 males and 2 females;age (46.5±10.0) years (range:33 to 63 years);141 cases in the non-biliary stricture group,including 89 males and 52 females;age (41.9±10.8) years (range: 20 to 71 years); there were statistically significant differences between the two groups in the proportions of infected pancreatic necrosis,pancreatic head necrosis,and lower extremity venous thrombosis (all P<0.05);the time from the onset of SAP to the diagnosis of biliary stenosis in patients with biliary stenosis was 2.0 (3.0) months (range: 1 to 19 months). Univariate analysis was performed using independent sample t-test, Mann-Whitney U test, χ 2 test,or Fisher′s exact probability method,and variables with P<0.05 in univariate analysis were included in multivariate logistic regression analysis. The receiver operating characteristic (ROC) curve was used to analyze the diagnostic and predictive value of the multivariate logistic regression model for AAC and biliary stricture. Results:There were statistically significant differences in fasting time,Balthazar-CTSI score,admission total bilirubin,and the proportions of concurrent shock and sepsis between the AAC group and non-AAC group ( P<0.05). Multivariate logistic analysis showed that admission total bilirubin ( OR=1.033,95% CI: 1.010 to 1.058, P=0.004),Balthazar-CTSI score ( OR=1.276,95% CI: 1.036 to 1.572, P=0.022),fasting time ( OR=1.127,95% CI: 1.044 to 1.216, P=0.002), and sepsis ( OR=4.033, 95% CI: 1.419 to 11.462, P=0.009) were independent risk factors for AAC complicated by SAP. The area under the curve (AUC) of the ROC curve was 0.820 (95% CI: 0.752 to 0.888). There were statistically significant differences in the proportions of infected pancreatic necrosis,pancreatic head necrosis,and lower extremity venous thrombosis between the biliary stricture group and non-biliary stricture group ( P<0.05). Multivariate logistic analysis showed that infected pancreatic necrosis ( OR=7.376,95% CI:1.566 to 37.750, P=0.012) and pancreatic head necrosis ( OR=3.898,95% CI:1.180 to 12.877, P=0.026) were independent risk factors for biliary stricture complicated by SAP. The AUC of the ROC curve was 0.806 (95% CI:0.715 to 0.898). Conclusions:AAC typically occurs in the early stage of SAP,and biliary stricture usually occurs in the late stage of SAP. Admission total bilirubin,Balthazar-CTSI score,fasting duration,and concurrent sepsis are independent risk factors for AAC complicating SAP. Infected pancreatic necrosis and pancreatic head necrosis are independent risk factors for biliary stricture complicating SAP.
10.Finite element analysis of various root shield thicknesses in maxillary central incisor socket-shield technique
Guangneng CHEN ; Siyang LUO ; Mei WANG ; Bin YE ; Jiawen CHEN ; Yin LIU ; Yuwen ZUO ; Xianyu HE ; Jiajin SHEN ; Minxian MA
Chinese Journal of Tissue Engineering Research 2025;29(10):2052-2060
BACKGROUND:Socket-shield technique can effectively maintain labial soft and hard tissues,but the incidence of postoperative complications such as exposure and displacement of root shield is relatively high.It is speculated that the root shield may be exposed and displaced due to excessive load after long-term function of dental implants. OBJECTIVE:Through three-dimensional finite element analysis,we aim to study the influence of varying root shield thicknesses on the stress distribution,equivalent stress peaks,and displacement in the root shield,periodontal ligaments,implant,and surrounding alveolar bone under normal occlusal loading.We also attempt to analyze the correlation between the thickness of the root shield and occurrence of mechanical events such as root shield exposure,displacement,and fracture. METHODS:Cone-beam CT data of a patient who met the indication standard of socket-shield technique for maxillary central incisor were retrieved from database.Reverse engineering techniques were used to build models of the maxillary bone and root shield,while forward engineering was used to create models for the implant components based on their parameters.Models depicting various root shield thicknesses(0.5,1.0,1.5,and 2.0 mm)were created using Solidworks 2022 software.ANSYS Workbench 2021 software was then used to simulate and analyze the effects of varying root shield thicknesses on stress distribution,equivalent stress peaks,and displacement of the root shields,periodontal ligaments,implants,and surrounding alveolar bone under normal occlusion. RESULTS AND CONCLUSION:(1)In all root shield models,the stress was concentrated on the palatal cervical side,both sides of the edges and the lower edge of the labial side.As the thickness of the root shield increased,the equivalent stress peak and displacement showed a decreasing trend.The 0.5 mm thickness model produced a stress concentration of 176.20 MPa,which exceeded the yield strength(150 MPa)of tooth tissue.(2)The periodontal ligament stress in each group was concentrated in the neck margin and upper region.With the increase of root shield thickness,the equivalent stress peak and displacement of periodontal ligament showed a decreasing trend.(3)Implant stress in all models was concentrated in the neck of the implant and the joint of the implant-repair abutment,and the labial side was more concentrated than the palatal side.With the increase of root shield thickness,the equivalent stress peak of the implant in the model showed an increasing trend.(4)In each group of models,stress of cortical bone concentrated around the neck of the implant and the periphery of the root shield,and the labial side was more concentrated than the palatal side.With the increase of the thickness of the root shield,the equivalent stress peak around the root shield decreased;the peak value of the equivalent stress of the bone around the neck of the implant showed an increasing trend.In the model,the stress of cancellous bone was mainly concentrated around the neck of the lip of the implant,the top of the thread,the root tip and the lower margin of the root shield,and the labial side was more concentrated than the palatal side.With the increase of the thickness of the root shield,the peak value of the equivalent stress of the bone around the root shield in the model showed a decreasing trend.The minimum principal stress of cortical bone in each group of models was concentrated around the neck of the implant,exhibiting a fan-shaped distribution.As the thickness of the root shield increased,the minimum principal stress of cortical bone showed an increasing trend.(5)These results indicate that different thicknesses of the root shield have different biomechanical effects.The root shield with a thickness of 0.5 mm is easy to fracture.For patients with sufficient bone width,the root shield with a thickness of 2.0 mm is an option to reduce the risk of complications such as root shield exposure,fracture,and displacement.Meanwhile,it should be taken into account to protect the periodontal ligament in the preparation process,and rounding treatments ought to be carried out on both sides and the lower edge of the root shield.

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