1.Meta-analysis of influential factors for all-cause mortality in patients with carbapenem-resistant Gram-negative bacteria treated with polymyxin B
Ruijuan TAN ; Lidan WANG ; Mei DU ; Hongfang MA ; Xiaoyan ZHANG
China Pharmacy 2026;37(7):949-953
OBJECTIVE To systematically evaluate the influential factors for all-cause mortality in patients with carbapenem-resistant Gram-negative bacteria (CR-GNB) treated with polymyxin B. METHODS PubMed, Embase, the Cochrane Library, Web of Science, Wanfang Data, VIP, CBM and CNKI were searched to collect clinical studies on all-cause death within 30 days or 28 days after treatment with polymyxin B in patients with CR-GNB infection from database establishment to July 2025. After literature screening, data extraction and evaluation of literature quality, meta-analysis was performed using RevMan 5.4 software. RESULTS A total of 12 studies were included, involving 1 326 patients, among whom 529 patients died, with a mortality rate of 39.89%. Meta-analysis results showed that combined with cardiovascular disease [OR=2.06, 95%CI (1.37, 3.09), P =0.005 ] , increased Sequential Organ Failure Assessment (SOFA) score [OR=1.20, 95%CI (1.07, 1.35), P =0.003 ] , mechanical ventilation [OR=2.35, 95%CI (1.65, 3.34), P <0.001 ] , continuous renal replacement therapy (CRRT) [OR=2.58, 95%CI (1.67, 3.97), P <0.001 ] , bloodstream infection [OR=3.24, 95%CI (2.19, 4.78), P <0.001 ] , multiple-site infection [OR=1.51, 95%CI (1.03, 2.20), P =0.03 ] , septic shock [OR=3.19, 95%CI (1.94, 5.24), P <0.001 ] , use of vasoactive drugs [OR=2.90, 95%CI (1.97, 4.27), P <0.001 ] , and the occurrence of acute kidney injury (AKI) [OR=2.17, 95%CI (1.41, 3.36), P <0.001 ] were risk factors for all-cause mortality in patients with CR-GNB infection treated with polymyxin B. Conversely, an extended duration of polymy xin B treatment [OR=0.92, 95%CI (0.86, 0.99), P =0.03 ] and early administration after CR-GNB infection [OR=0.47, 95%CI (0.25, 0.85), P =0.01 ] were protective factors. CONCLUSIONS Patients with cardiovascular disease, receiving mechanical ventilation or CRRT, having bloodstream infection, multiple-site infection or septic shock, combining with vasoactive drugs, with AKI and increased SOFA scores have a higher risk of all-cause mortality. Conversely, extending the duration of polymyxin B treatment (beyond 7 days) and early administration within 48 hours after confirmed CR-GNB infection can significantly reduce the risk of all-cause mortality.
2.Nanopackaged Astaxanthin Improves Demyelination in Multiple Sclerosis Model Mice by Scavenging Excessive Endogenous Formaldehyde
Wan-Jia LÜ ; Xin ZENG ; Zhi-Qian TONG ; Yang XING ; Xu YANG ; Mei-Na WU ; Ping MA
Progress in Biochemistry and Biophysics 2026;53(2):442-457
ObjectiveMultiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS); however, its underlying neurological pathogenic mechanisms remain incompletely understood. Endogenous formaldehyde (FA), a metabolic byproduct of methylation-demethylation cycles, has recently been implicated in neurotoxicity, oxidative damage, and cognitive impairment. This study aimed to investigate whether excessive FA contributes to myelin sheath demyelination in mice and to evaluate the protective effects and mechanisms of two FA-elimination strategies: sodium bisulfite (NaHSO3), a classical FA scavenger, and polyethylene glycol-modified astaxanthin nanoparticles (PEG-ATX@NPs), a brain-targeted nano-antioxidant formulation. MethodsA chronic demyelination model was established by feeding female C57BL/6J mice a diet containing 0.2% cuprizone (CPZ) for four weeks, followed by a two-week intervention period. Eighty mice were randomly assigned to four groups: NS (normal saline), CPZ+NS, CPZ+NaHSO3, and CPZ+PEG-ATX@NPs. Behavioral tests, including open-field, Y-maze, and pole-climbing assays, were conducted to assess locomotor activity, motor coordination, and working memory. FA levels in serum, corpus callosum, and spinal cord were measured using an Na-FA fluorescent probe and quantified via in vivo and ex vivo fluorescence imaging. Neuroinflammatory responses were evaluated by measuring TNF-α, IL-1β, and IL-6 levels using ELISA, while oxidative stress was assessed by reactive oxygen species (ROS) fluorescence intensity. Demyelination was examined via Luxol fast blue staining, and microglial activation was analyzed by Iba1 immunofluorescence. Correlation analyses were performed to explore relationships among FA levels, inflammatory cytokines, ROS intensity, and behavioral parameters. ResultsCompared with the NS group, mice in the CPZ+NS group exhibited significant weight loss, impaired motor coordination and memory, and markedly reduced myelin regeneration (P<0.05). FA levels and pro-inflammatory cytokines were significantly elevated in serum, corpus callosum, and spinal cord (P<0.05). FA-associated fluorescence in brain and spinal tissues, as well as ROS intensity across all tissues examined, also increased substantially (P<0.05). CPZ treatment induced pronounced microglial activation and severe demyelination in the corpus callosum (P<0.01). Both NaHSO3 and PEG-ATX@NPs effectively reduced FA accumulation in the brain and spinal cord, attenuated demyelination, suppressed microglial activation, decreased inflammatory cytokine levels, and improved motor and cognitive performance. These results confirm that CPZ induced severe demyelination accompanied by oxidative stress, neuroinflammation, and abnormal FA accumulation. Following intervention with either NaHSO3 or PEG-ATX@NPs, endogenous FA levels in the CNS were substantially reduced. Both treatments alleviated demyelination and significantly decreased the number of activated microglia. Levels of TNF-α, IL-1β, and IL-6 in serum, corpus callosum, and spinal cord were downregulated. Behavioral performance improved significantly, as evidenced by enhanced locomotor activity, better coordination, and improved memory function. These findings indicate that both FA-scavenging agents mitigate CPZ-induced biochemical and behavioral abnormalities. ConclusionThis study demonstrates that excessive endogenous FA is closely associated with cognitive impairment, inflammatory dysregulation, and demyelination in a CPZ-induced chronic demyelination mouse model. Clearing abnormally elevated FA effectively reduces neuroinflammation, suppresses microglial overactivation, decreases oxidative stress, and alleviates demyelination, ultimately improving motor and cognitive outcomes in mice. These results suggest that targeting endogenous FA represents a promising therapeutic strategy for MS and other demyelinating disorders. Further investigations are warranted to explore the long-term safety, dosage optimization, and molecular pathways involved in FA-mediated neurotoxicity.
3.Nanopackaged Astaxanthin Improves Demyelination in Multiple Sclerosis Model Mice by Scavenging Excessive Endogenous Formaldehyde
Wan-Jia LÜ ; Xin ZENG ; Zhi-Qian TONG ; Yang XING ; Xu YANG ; Mei-Na WU ; Ping MA
Progress in Biochemistry and Biophysics 2026;53(2):442-457
ObjectiveMultiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS); however, its underlying neurological pathogenic mechanisms remain incompletely understood. Endogenous formaldehyde (FA), a metabolic byproduct of methylation-demethylation cycles, has recently been implicated in neurotoxicity, oxidative damage, and cognitive impairment. This study aimed to investigate whether excessive FA contributes to myelin sheath demyelination in mice and to evaluate the protective effects and mechanisms of two FA-elimination strategies: sodium bisulfite (NaHSO3), a classical FA scavenger, and polyethylene glycol-modified astaxanthin nanoparticles (PEG-ATX@NPs), a brain-targeted nano-antioxidant formulation. MethodsA chronic demyelination model was established by feeding female C57BL/6J mice a diet containing 0.2% cuprizone (CPZ) for four weeks, followed by a two-week intervention period. Eighty mice were randomly assigned to four groups: NS (normal saline), CPZ+NS, CPZ+NaHSO3, and CPZ+PEG-ATX@NPs. Behavioral tests, including open-field, Y-maze, and pole-climbing assays, were conducted to assess locomotor activity, motor coordination, and working memory. FA levels in serum, corpus callosum, and spinal cord were measured using an Na-FA fluorescent probe and quantified via in vivo and ex vivo fluorescence imaging. Neuroinflammatory responses were evaluated by measuring TNF-α, IL-1β, and IL-6 levels using ELISA, while oxidative stress was assessed by reactive oxygen species (ROS) fluorescence intensity. Demyelination was examined via Luxol fast blue staining, and microglial activation was analyzed by Iba1 immunofluorescence. Correlation analyses were performed to explore relationships among FA levels, inflammatory cytokines, ROS intensity, and behavioral parameters. ResultsCompared with the NS group, mice in the CPZ+NS group exhibited significant weight loss, impaired motor coordination and memory, and markedly reduced myelin regeneration (P<0.05). FA levels and pro-inflammatory cytokines were significantly elevated in serum, corpus callosum, and spinal cord (P<0.05). FA-associated fluorescence in brain and spinal tissues, as well as ROS intensity across all tissues examined, also increased substantially (P<0.05). CPZ treatment induced pronounced microglial activation and severe demyelination in the corpus callosum (P<0.01). Both NaHSO3 and PEG-ATX@NPs effectively reduced FA accumulation in the brain and spinal cord, attenuated demyelination, suppressed microglial activation, decreased inflammatory cytokine levels, and improved motor and cognitive performance. These results confirm that CPZ induced severe demyelination accompanied by oxidative stress, neuroinflammation, and abnormal FA accumulation. Following intervention with either NaHSO3 or PEG-ATX@NPs, endogenous FA levels in the CNS were substantially reduced. Both treatments alleviated demyelination and significantly decreased the number of activated microglia. Levels of TNF-α, IL-1β, and IL-6 in serum, corpus callosum, and spinal cord were downregulated. Behavioral performance improved significantly, as evidenced by enhanced locomotor activity, better coordination, and improved memory function. These findings indicate that both FA-scavenging agents mitigate CPZ-induced biochemical and behavioral abnormalities. ConclusionThis study demonstrates that excessive endogenous FA is closely associated with cognitive impairment, inflammatory dysregulation, and demyelination in a CPZ-induced chronic demyelination mouse model. Clearing abnormally elevated FA effectively reduces neuroinflammation, suppresses microglial overactivation, decreases oxidative stress, and alleviates demyelination, ultimately improving motor and cognitive outcomes in mice. These results suggest that targeting endogenous FA represents a promising therapeutic strategy for MS and other demyelinating disorders. Further investigations are warranted to explore the long-term safety, dosage optimization, and molecular pathways involved in FA-mediated neurotoxicity.
4.Pathogenic analysis of Campylobacter jejuni in Fengtai District
Zhaoe WANG ; Mei QU ; Huiru FENG ; Zhuo MA ; Zhimin ZHANG
Journal of Public Health and Preventive Medicine 2026;37(4):71-75
Objective To investigate the drug resistance phenotype/genotype and virulence gene carrying status, serotype, and sequence typing (ST) of Campylobacter jejuni in Fengtai District in 2024. Methods The drug resistance phenotype was detected by agar dilution method, and serotyping was performed by real-time fluorescence quantitative polymerase chain reaction (PCR). The whole genome sequencing was used to analyze drug resistance genes, virulence genes, and other characteristics. Results Among the 35 Campylobacter jejuni strains analyzed, the antibiotics with the highest resistance rates were nalidixic acid and ciprofloxacin (both 82.86%), followed by tetracycline (74.89%). All strains exhibited a 100.00% sensitivity rate to erythromycin. The multiple drug resistance rate was 77.14%. The predominant drug resistance genes were gyrA-T86I (94.29%) and tetO (74.29%). The most common serotype was HS:2, accounting for 25 strains. A total of 132 virulence genes were detected. There were 12 clonal complexes (CC) and 24 ST types. Conclusion The drug resistance situation of Campylobacter jejuni in Fengtai District is relatively severe, and the drug resistance phenotype is related to specific genetic mutations to some extent. The serotypes are diverse, the virulence genes are complex, and the pathogenic potential is significant, posing a notable risk for inducing Guillain-Barré syndrome (GBS). The high number of ST types indicates substantial genetic diversity.
5.Chinese expert consensus on the application of jejunal interposition for esophageal reconstruction in complex esophageal cancer surgery (2026 edition)
Wenshu CHEN ; Lilan ZHAO ; Zhaoxian LIN ; Debin OU ; Zhigang LI ; Chengchu ZHU ; Longqi CHEN ; Shuoyan LIU ; Xiangnan LI ; Chao CHENG ; Ni ZHANG ; Songping XIE ; Xufeng GUO ; Xu LI ; Xinyu MEI ; Xuefeng LENG ; Jianqun MA ; Zhijun HUANG ; Guojun GENG ; Lin ZHANG ; Hongyan WANG ; Yi ZHANG ; Weijie WANG ; Jiangbo LIN ; Jinbiao XIE ; Jun GUAN ; Rongqi HE ; Xing LIN ; Xiuhua TU ; Yong LI ; Lijie TAN ; Xiaojie PAN
Chinese Journal of Clinical Thoracic and Cardiovascular Surgery 2026;33(10):1527-1543
Objective Jejunal interposition is an important option for restoring gastrointestinal continuity in patients with complex esophageal cancer in whom the stomach is unavailable for reconstruction due to previous gastrectomy, tumor involvement, failed gastric conduit, or other constraints. Although the jejunum offers a caliber similar to the esophagus, a rich blood supply, and preserved peristaltic function, anatomical variations in mesenteric length and vascular arcades render long-segment and high-level reconstruction susceptible to excessive tension, mesenteric torsion, venous congestion, and inadequate distal perfusion. This consensus aims to provide standardized recommendations for the application of jejunal interposition in this specific patient population. Methods This consensus was developed in accordance with the WHO Handbook for Guideline Development and Chinese national guideline development standards, with reference to the Appraisal of Guidelines for Research & Evaluation Ⅱ(AGREE Ⅱ), Reporting Items for Practice Guidelines in Healthcare (RIGHT), and Scientific, Transparent and Applicable Rankings (STAR) checklists. The project was registered on the international practice guidelines registry platform (PREPARE-2026CN1384). The working group systematically searched Chinese and English evidence addressing 12 clinical questions. Evidence was graded using the Oxford Centre for Evidence-Based Medicine (OCEBM) 2009 system, with structured appraisal of risk of bias, inconsistency, indirectness, and imprecision. Recommendations were formulated through two rounds of Delphi surveys and a face-to-face consensus meeting, with an agreement threshold of ≥75%. Results The consensus generated 12 recommendations covering indications, selection between jejunum and colon, preoperative assessment, surgical approach and reconstruction route, pedicled jejunal interposition (PJI), supercharged pedicled jejunal interposition (SPJ), indocyanine green (ICG) perfusion assessment, perioperative nutrition, management of anastomotic leakage, long-term follow-up, and special treatment scenarios. Given that the available direct evidence is predominantly derived from single-center retrospective cohorts and case series, recommendations extrapolated from general esophagectomy or other gastrointestinal surgical evidence are deliberately phrased with caution. Conclusion Jejunal interposition is a safe and effective approach for digestive tract reconstruction in patients with complex esophageal cancer in whom the stomach is unavailable. This consensus emphasizes that clinical decision-making should be individualized based on the patient's prior treatment history, reconstruction height, vascular anatomy, technical availability, and institutional experience in the Chinese context.
6.Mechanism of Zuoguiwan in Inhibiting Osteoclast Activation Induced by Breast Cancer via Regulating p38 MAPK/ERK Signaling Pathway
Jianjiang FU ; Yinlong MEI ; Junchao MA ; Xiaocui ZHU ; Wei WANG ; Hong LYU
Chinese Journal of Experimental Traditional Medical Formulae 2025;31(1):1-9
ObjectiveTo investigate the effects of Zuoguiwan on osteoclast activation induced by breast cancer and its mechanism. MethodsTo simulate breast cancer-induced osteoclastic bone metastasis, RAW264.7 cells were cultured in conditioned medium containing 50% supernatant of MDA-MB-231 breast cancer cells. The dosages of Zuoguiwan used in the experiment were sera containing 5% and 10% Zuoguiwan. Tartrate-resistant acid phosphatase (TRAP) staining was used to detect osteoclast activation. Enzyme-linked immunosorbent assay (ELISA) was used to measure Cathepsin K secretion from RAW264.7 cells. Real-time quantitative polymerase chain reaction (PCR) was used to detect the mRNA expression levels of osteocalcin (OCN) and bone sialoprotein (BSP). Immunoprecipitation was employed to detect the interaction between Runt-related transcription factor 2 (Runx2) and core binding factor β subunit (CBF-β). Western blot was used to assess the protein expression of Runx2, phosphorylated Runx2 (p-Runx2), extracellular signal-regulated kinases 1/2 (ERK1/2), p-ERK1/2, p38 mitogen-activated protein kinase (MAPK), p-p38 MAPK, and CBF-β. ResultsCompared with the blank group, the MDA-MB-231 cell supernatant group showed a significant increase in TRAP-positive cell counts and Cathepsin K secretion. Meanwhile, the expression levels of p-Runx2, Runx2-CBF-β interaction, BSP and OCN mRNA, p-p38 MAPK, and p-ERK1/2 proteins were significantly decreased (P<0.01). Compared with the MDA-MB-231 cell supernatant group, Zuoguiwan-containing sera significantly reduced TRAP-positive cell counts and Cathepsin K secretion (P<0.01), significantly increased p-Runx2, BSP and OCN mRNA expression, as well as p-p38 MAPK and p-ERK1/2 protein levels, and promoted the interaction between Runx2 and CBF-β (P<0.01). No significant change in Runx2 expression was observed. Compared to the blank group, the BVD-523 group showed significantly lower expression of p-p38 MAPK and p-ERK1/2 proteins (P<0.01). Compared with the BVD-523 group, both low and high concentration Zuoguiwan-containing sera groups showed significantly higher p-p38 MAPK expression (P<0.01), and the high concentration Zuoguiwan group also exhibited a significant increase in p-ERK1/2 expression (P<0.01), while no statistical difference was found in the low-dose group. ConclusionZuoguiwan inhibits osteoclast activation by inducing phosphorylation of the key transcriptional regulator Runx2 in intra-osteoclast bone formation, and this process is closely associated with the activation of the p38 MAPK/ERK signaling pathway.
7.Usefulness of intraoperative choledochoscopy in laparoscopic subtotal cholecystectomy for severe cholecystitis
Rui-Hui ZHANG ; Xiang-Nan WANG ; Yue-Feng MA ; Xue-Qian TANG ; Mei-Ju LIN ; Li-Jun SHI ; Jing-Yi LI ; Hong-Wei ZHANG
Annals of Hepato-Biliary-Pancreatic Surgery 2025;29(2):192-198
Laparoscopic subtotal cholecystectomy (LSC) has been a safe and viable alternative to conversion to laparotomy in cases of severe cholecystitis. The objective of this study is to determine the utility of intraoperative choledochoscopy in LSC for the exploration of the gallbladder, cyst duct, and subsequent stone clearance of the cystic duct in cases of severe cholecystitis. A total of 72 patients diagnosed with severe cholecystitis received choledochoscopy-assisted laparoscopic subtotal cholecystectomy (CALSC). A choledochoscopy was performed to explore the gallbladder cavity and/or cystic duct, and to extract stones using a range of techniques. The clinical records, including the operative records and outcomes, were subjected to analysis. No LSC was converted to open surgery, and no bile duct or vascular injuries were sustained. All stones within the cystic duct were removed by a combination of techniques, including high-frequency needle knife electrotomy, basket, and electrohydraulic lithotripsy. A follow-up examination revealed the absence of residual bile duct stones, with the exception of one common bile duct stone, which was extracted via endoscopic retrograde cholangiopancreatography. In certain special cases, CALSC may prove to be an efficacious treatment for the management of severe cholecystitis. This technique allows for optimal comprehension of the situation within the gallbladder cavity and cystic duct, facilitating the removal of stones from the cystic duct and reducing the residue of the non-functional gallbladder remnant.
9.GOLM1 promotes cholesterol gallstone formation via ABCG5-mediated cholesterol efflux in metabolic dysfunction-associated steatohepatitis livers
Yi-Tong LI ; Wei-Qing SHAO ; Zhen-Mei CHEN ; Xiao-Chen MA ; Chen-He YI ; Bao-Rui TAO ; Bo ZHANG ; Yue MA ; Guo ZHANG ; Rui ZHANG ; Yan GENG ; Jing LIN ; Jin-Hong CHEN
Clinical and Molecular Hepatology 2025;31(2):409-425
Background/Aims:
Metabolic dysfunction-associated steatohepatitis (MASH) is a significant risk factor for gallstone formation, but mechanisms underlying MASH-related gallstone formation remain unclear. Golgi membrane protein 1 (GOLM1) participates in hepatic cholesterol metabolism and is upregulated in MASH. Here, we aimed to explore the role of GOLM1 in MASH-related gallstone formation.
Methods:
The UK Biobank cohort was used for etiological analysis. GOLM1 knockout (GOLM1-/-) and wild-type (WT) mice were fed with a high-fat diet (HFD). Livers were excised for histology and immunohistochemistry analysis. Gallbladders were collected to calculate incidence of cholesterol gallstones (CGSs). Biles were collected for biliary lipid analysis. HepG2 cells were used to explore underlying mechanisms. Human liver samples were used for clinical validation.
Results:
MASH patients had a greater risk of cholelithiasis. All HFD-fed mice developed MASH, and the incidence of gallstones was 16.7% and 75.0% in GOLM1-/- and WT mice, respectively. GOLM1-/- decreased biliary cholesterol concentration and output. In vivo and in vitro assays confirmed that GOLM1 facilitated cholesterol efflux through upregulating ATP binding cassette transporter subfamily G member 5 (ABCG5). Mechanistically, GOLM1 translocated into nucleus to promote osteopontin (OPN) transcription, thus stimulating ABCG5-mediated cholesterol efflux. Moreover, GOLM1 was upregulated by interleukin-1β (IL-1β) in a dose-dependent manner. Finally, we confirmed that IL-1β, GOLM1, OPN, and ABCG5 were enhanced in livers of MASH patients with CGSs.
Conclusions
In MASH livers, upregulation of GOLM1 by IL-1β increases ABCG5-mediated cholesterol efflux in an OPN-dependent manner, promoting CGS formation. GOLM1 has the potential to be a molecular hub interconnecting MASH and CGSs.
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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