BACKGROUND:One of the advantages of clear aligner treatment is molar distalization.However,tooth tilting movement and loss of anterior anchorage may occur during treatment.There are few studies on whether these problems can be improved by selecting clear aligners with different thicknesses and edges to improve the clinical treatment effect.OBJECTIVE:To analyze the control ability of clear aligners with different thickness and edges on the central incisor,lateral incisor,and second molar when pushing the maxillary second molar distally by three-dimensional finite element analysis.METHODS:Three-dimensional finite element analysis models of bilateral maxillary second molar distalization with clear aligner,maxillary dentition,periodontal ligament,and alveolar bone with different thicknesses and margins were established by Mimics,Geomagic Wrap,3-matic and SolidWorks software,respectively.There were 16 combinations of four thicknesses(0.4,0.5,0.625,and 0.75 mm)and four margins(scallop,straight,straight extension 2 mm and straight extension 4 mm).The data were imported into Ansys Workbench software for design and solution.The mean value,peak value and distribution of the periodontal ligament equivalent stress of the second molar,the equivalent stress and the maximum initial displacement of the second molar,and the control ability of each appliance on the second molar,central incisor,and lateral incisor were analyzed.RESULTS AND CONCLUSION:(1)The mean equivalent stress of periodontal ligament of the second molar,the equivalent stress of the second molar and the maximum initial displacement of the second molar increased with the extension of the appliance edge and the increase of the thickness of the appliance in the 16 groups of models.(2)When the thickness of appliances was the same,the maximum equivalent stress of the second molar in the linear appliance group was the highest,and the maximum equivalent stress of the second molar in the linear extended appliance group was greater than that in the scallop appliance group.When the edge of the appliance was the same,the periodontal ligament equivalent stress peak of the second molar increased with the increase of the thickness of the appliance.The equivalent stress distribution in the periodontal ligament of the second molar in the linear extendable appliance group was more uniform than that in the scallop appliance group and the linear appliance group.(3)When the thickness of the appliance was the same,the scallop-shaped appliance had the worst control on the second molar.When the edge of the appliance was the same,with the increase of the thickness of the appliance,the control of the second molar by the linear extender appliance was gradually stronger than that by the linear appliance.The control of the central incisor was stronger and more stable with the linear extended 2 mm appliance,while the control of the lateral incisor was stronger and more stable with the linear appliance.(4)The results showed that when using clear aligners to push molars distally,extending the edge of the appliance could improve the control of the molars and reduce the tilting movement of the teeth.The design of a straight extension margin of 2 mm for the central incisor and a straight edge for the lateral incisor can enhance the control of the anchorage incisor and reduce the labial inclination of the anterior teeth.

BACKGROUND:One of the advantages of clear aligner treatment is molar distalization.However,tooth tilting movement and loss of anterior anchorage may occur during treatment.There are few studies on whether these problems can be improved by selecting clear aligners with different thicknesses and edges to improve the clinical treatment effect.OBJECTIVE:To analyze the control ability of clear aligners with different thickness and edges on the central incisor,lateral incisor,and second molar when pushing the maxillary second molar distally by three-dimensional finite element analysis.METHODS:Three-dimensional finite element analysis models of bilateral maxillary second molar distalization with clear aligner,maxillary dentition,periodontal ligament,and alveolar bone with different thicknesses and margins were established by Mimics,Geomagic Wrap,3-matic and SolidWorks software,respectively.There were 16 combinations of four thicknesses(0.4,0.5,0.625,and 0.75 mm)and four margins(scallop,straight,straight extension 2 mm and straight extension 4 mm).The data were imported into Ansys Workbench software for design and solution.The mean value,peak value and distribution of the periodontal ligament equivalent stress of the second molar,the equivalent stress and the maximum initial displacement of the second molar,and the control ability of each appliance on the second molar,central incisor,and lateral incisor were analyzed.RESULTS AND CONCLUSION:(1)The mean equivalent stress of periodontal ligament of the second molar,the equivalent stress of the second molar and the maximum initial displacement of the second molar increased with the extension of the appliance edge and the increase of the thickness of the appliance in the 16 groups of models.(2)When the thickness of appliances was the same,the maximum equivalent stress of the second molar in the linear appliance group was the highest,and the maximum equivalent stress of the second molar in the linear extended appliance group was greater than that in the scallop appliance group.When the edge of the appliance was the same,the periodontal ligament equivalent stress peak of the second molar increased with the increase of the thickness of the appliance.The equivalent stress distribution in the periodontal ligament of the second molar in the linear extendable appliance group was more uniform than that in the scallop appliance group and the linear appliance group.(3)When the thickness of the appliance was the same,the scallop-shaped appliance had the worst control on the second molar.When the edge of the appliance was the same,with the increase of the thickness of the appliance,the control of the second molar by the linear extender appliance was gradually stronger than that by the linear appliance.The control of the central incisor was stronger and more stable with the linear extended 2 mm appliance,while the control of the lateral incisor was stronger and more stable with the linear appliance.(4)The results showed that when using clear aligners to push molars distally,extending the edge of the appliance could improve the control of the molars and reduce the tilting movement of the teeth.The design of a straight extension margin of 2 mm for the central incisor and a straight edge for the lateral incisor can enhance the control of the anchorage incisor and reduce the labial inclination of the anterior teeth.

Objective:To investigate the predictive value of C-reactive protein to lymphocyte ratio (CLR) for stroke-associated pneumonia (SAP).Methods:Consecutive patients with acute ischemic stroke admitted to the Department of Neurology, Guangming Ophthalmic Hospital from September 2018 to December 2020 were enrolled retrospectively. Fasting venous blood was taken the next morning after admission to detect the levels of C-reactive protein and lymphocytes. The baseline clinical data of the patients in the SAP group and the non-SAP group were compared. Multivariate logistic regression analysis was used to identify the independent predictors of SAP. The predictive value of CLR for SAP was evaluated by receiver operator characteristic (ROC) curve analysis. Results:A total of 479 patients with acute ischemic stroke were included. The median CLR was 3.69×10 -9, 81 patients (16.9%) had SAP. The incidence of SAP in the high CLR group was significantly higher than that in the low CLR group (26.7% vs. 7.1%; P=0.001). Univariate analysis showed that there were significant differences in age, atrial fibrillation, dysphagia, baseline National Institutes of Health Stroke Scale score, stroke etiology type, leukocyte count, fasting blood glucose, total cholesterol and CLR between the SAP group and the non-SAP group (all P<0.05). Multivariate logistic regression analysis showed that after adjusting for confounding factors, CLR was an independent predictor of SAP (odds ratio 3.472, 95% confidence interval 1.431-14.706; P=0.013). ROC curve analysis showed that the area under the curve of CLR predicting SAP was 0.735 (95% confidence interval 0.693-0.774; P<0.001). The optimal cut-off value was 6.14 ×10 -9. The sensitivity and specificity were 69.1% and 72.6% respectively. Conclusion:Higher baseline CLR can predict SAP risk in patients with acute ischemic stroke.

Objective To study the pathological and immunohistochemical features of alimentary tract mesenchymal tumors and compare with computed tomographic virtue endoscopy (CTVE) imaging technology to evaluate the diagnostic value of CTVE in alimentary tract mesenchymal tumors. Methods Seventy-four pathological specimens of alimentary tract mesenchymal tumors were collected. The pathological features and the expression of CD117, CD34, SMA and S-100 were observed by immunohistochemical method with light microscope. The pathological types and characteristics were determined by pathologists and compared with CTVE imaging technology. Results In the 74 cases of alimentary tract mesenchymal tumors,40 cases were diagnosed as stromal tumor with pathological and immunohistochemical methods (54. 1%).Sixteen of them were malignant, accounting for 40% of the stromal tumor while 33 cases were diagnosed as leiomyoma(44. 6%)and 1 case as schwannoma(1.4%) . In the 74 GIMTs cases ,33 were jejunum GIMTs,21 were ileum GIMTs and 20 were large intestine GIMTs. Immunohistochemistry assay in the 74 GIMTs cases showed that 51.4% GIMTs were positive for CD117, approximately 36. 5% were positive for CD34 , 62.2% were positive for smooth-muscle actin (SMA) and 1. 4% were positive for S-100 protein. In the 74 GIMTs cases,69 cases were diagnosed right in the accuracy for location with CTVE(93. 2%) with 51 cases in small intestinal (94. 4%) and 18 cases in large intestinal (90. 0%). The sensitivity and the specificity of CTVE to distinguish benign from malignant stromal tumors by CTVE characteristics were 84. 2% and 85. 7%respectively. Conclusions GIST is common in GIMTs and is often originated from the small intestinal. The immunohistochemistry has great value in diagnosing alimentary tract mesenchymal tumors. The CTVE imaging technology also has great value in diagnosing alimentary tract mesenchymal tumors which can show the localization, shape size and artery of the tumor clearly. The diagnostic sensitivity and specificity of CTVE are high to distinguish benign from malignant alimentary tract GISTs. CTVE plays an important role in guiding the clinical management of GISTs.