ABSTRACT
Objective To explore the effect of attachment wear on tooth movement in clear Aligner treatment, and to provide references for improving the efficiency of orthodontic treatment. Methods The tooth cone bean computed tomography (CBCT) scanning data were obtained, and the tooth model was established and assembled with the worn and complete attachment, respectively. When the appliance applied 2° distal torsion, 0.25 mm distal displacement, 0.1 mm depression displacement and 0.1 mm elongation displacement to the teeth, the changes of tooth displacement, periodontal ligament stress and root equivalent stress in the worn and complete attachment groups were compared. Results When the clear Aligner was used to apply distal torsion and elongation displacement to the teeth, the maximum tooth displacement decreased significantly, and the worn attachment caused the teeth to move obliquely when the distal translation and elongation displacement occurred. When the tooth was subjected to distal torsion, distal translation, depression and elongation, the maximum principal stress of periodontal ligament and the equivalent stress of tooth root decreased when the worn attachment caused the tooth to be subjected to distal torsion, distal translation, depression and elongation. Conclusions Attachment wear will affect the efficiency of tooth rotation and elongation.When the attachments are obviously worn, they should be replaced in time to ensure normal function of the attachments.
ABSTRACT
Objective:To collect the imaging data and related materials of the patients with in-stent restenosis (ISR)after coronary artery stent operation with intravascular ultrasound (IVUS),and to analyze the risk factors of ISR,and to propose the reasonable intervention strategies.Methods:Fifty patients with ISR were divided into ISR ≤ 50% drug group (n = 14 )and ISR > 50% drug group (n = 36),including drug-coated balloon therapy group (n=16)and stent treatment group (n=20);IVUS virtual organization technology was used to compare the plaque area,location,tissue composition,thrombus and other factors of the patients in various groups after treatment;the data changes after 6 months of follow-up were analyzed.Results:The IVUS results showed the plaque areas and plaque loads of the ISR patients treated with intervention were significantly reduced compared with before operation (P 0.05).Conclusion:The ISR rate is higher in the patients with high degree of fiber components,plaque composition heterogeneity and distribution of diffuse tortuous and calcified lesions.ISR has no significant correlation with the plaque wall thickness and lipid content and plaque instability and necrotic tissue proportion.