Numerical Analysis of Microcrack Propagation Characteristics and Influencing Factors of Serrated Structural Plane

The serrated structural plane is the basic unit of structural plane morphology. However, the understanding of its internal stress distribution, failure mode and crack evolution law was not clear enough in previous studies. In this paper, the shear mechanical properties of the serrated structural planes were studied by numerical simulation, and the crack evolution law of the serrated structural planes and the effects of four microscopic parameters on the shear properties were analyzed. The results show that: (1) the number of microcracks increases with the increase in normal stress; the crack expansion rate is slow before the shear stress reaches the peak. After the shear stress reaches the peak, the crack expansion rate continues to increase, and the microcracks keep sprouting and expanding, and the number of microcracks tends to stabilize when the shear stress reaches the residual shear strength. (2) The particle contact stiffness ratio kn∗/ks∗ and parallel bond stiffness ratio kn/ks were negatively correlated with the shear strength; and the particle contact modulus E and parallel bond modulus E∗ were positively correlated with the shear strength. As the particle contact modulus E and parallel bond modulus E∗ increase, the peak shear displacement gradually decreases. The parallel bond stiffness ratio kn/ks has a negative correlation with the peak shear displacement. This study is expected to provide theoretical guidance for the microscopic parameter calibration and shear mechanical analysis of serrated structural planes. (3) Several XGBoost, WOA-XGBoost, and PSO-XGBoost algorithms are introduced to construct the quantitative prediction model, and the comparative analysis found that WOA-XGBoost has the best fitting effect and can be used for the prediction of shear strength. When using this model to calculate the weight shares of micro-parameters, it was found that kn∗/ks∗ has the greatest influence on shear strength, followed by E∗; E and kn/ks had the least influence.     

Resin infiltration of deproteinised natural occlusal subsurface lesions improves initial quality of fissure sealing

The aim of this ex vivo study was to evaluate the infiltration capability and rate of microleakage of a low-viscous resin infiltrant combined with a flowable composite resin (RI/CR) when used with deproteinised and etched occlusal subsurface lesions (International Caries Detection and Assessment System code 2). This combined treatment procedure was compared with the exclusive use of flowable composite resin (CR) for fissure sealing. Twenty premolars and 20 molars revealing non-cavitated occlusal carious lesions were randomly divided into two groups and were meticulously cleaned and deproteinised using NaOCl (2%). After etching with HCl (15%), 10 premolar and 10 molar lesions were infiltrated (Icon/DMG; rhodamine B isothiocyanate (RITC)-labelled) followed by fissure sealing (G-?nial Flo/GC; experimental group, RI/CR). In the control group (CR), the carious fissures were only sealed. Specimens were cut perpendicular to the occlusal surface and through the area of the highest demineralisation (DIAGNOdent pen, KaVo). Using confocal laser-scanning microscopy, the specimens were assessed with regard to the percentage of caries infiltration, marginal adaption and internal integrity. Within the CR group, the carious lesions were not infiltrated. Both premolar (57.9%± 23.1%) and molar lesions (35.3%± 22.1%) of the RI/CR group were uniformly infiltrated to a substantial extent, albeit with significant differences (P=0.034). Moreover, microleakage (n=1) and the occurrence of voids (n=2) were reduced in the RI/CR group compared with the CR group (5 and 17 specimens, respectively). The RI/CR approach increases the initial quality of fissure sealing and is recommended for the clinical control of occlusal caries.     

Strained Lattice Gold-Copper Alloy Nanoparticles for Efficient Carbon Dioxide Electroreduction

Electrocatalytic conversion of carbon dioxide (CO₂) into specific renewable fuels is an attractive way to mitigate the greenhouse effect and solve the energy crisis. Au_nCu_100-n/C alloy nanoparticles (Au_nCu_100−n/C NPs) with tunable compositions, a highly active crystal plane and a strained lattice were synthesized by the thermal solvent co-reduction method. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) results show that Au_nCu_100−n/C catalysts display a subtle lattice strain and dominant (111) crystal plane, which can be adjusted by the alloy composition. Electrochemical results show that Au_nCu_100−n/C alloy catalysts for CO₂ reduction display high catalytic activity; in particular, the Faradaic efficiency of Au₇₅Cu₂₅/C is up to 92.6% for CO at −0.7 V (vs. the reversible hydrogen electrode), which is related to lattice shrinkage and the active facet. This research provides a new strategy with which to design strong and active nanoalloy catalysts with lattice mismatch and main active surfaces for CO₂ reduction reaction.     

蝶枕角与颅底诸结构至耳眼平面垂直距离的纵向比较

目的:为人颅底的生长发育研究提供正常的颅底结构测量数据和参照标准;初步分析颅底生长发育趋势和特点。方法:对人不同生长发育阶段颅底标本诸结构进行观察和测量,并对其进行相互比较和纵向分析。结果:颅底在不同发育阶段各有其趋势和特点,蝶枕角随着年龄的增长逐渐变小,但性别之间无差异,颅前窝诸结构变化幅度最大,颅中窝的变化相对最小,11项测量指标在不同生长发育阶段的变化各异。结论:观察测量数据可为人颅底生长发育进一步研究提供依据,蝶枕角、耳眼(FH)平面可作为颅底生长发育的观察测量指标和参照平面。     

下颈椎椎弓根轴线与椎板平面夹角的影像学测量及其临床意义

目的：探讨下颈椎椎弓根轴线与椎板平面夹角的影像学测量及其临床意义。方法：对排除颈椎畸形 的30例患者颈椎行三维重建CT扫描,在重建后的C3~C7特定CT图像上测量椎弓根轴线与椎板平面夹角。结果：1) C3~C7左右两侧横向椎弓根-同侧椎板角分别为98.3°±6.3°,98.0°±5.1°,97.5°±6.9°,95.1°±5.0°,85.8°±5.4°和96.7°±8.2°, 98.7°±7.1°,97.8°±3.6°,93.2°±6.2°,86.8°±5.7°;C3~C6的夹角大于90°,C7的夹角小于90°,呈逐渐减小趋势。除了C6与C3 和C7与其他节段外,其余各节段间的差异均无统计学意义(均P>0.05)。2)C3~C7左右两侧横向椎弓根-对侧椎板角分别 为0.2°±4.5°,1.2°±7.2°,–0.8°±6.8°,–3.3°±5.4°,–14.7°±4.0°和–1.6°±5.4°,1.9°±4.6°,–0.5°±6.0°,–4.6°±5.3°,–13.7°±3.4°, 呈先增大后减小趋势,C4的夹角最大。除了C6与C3,C6与C4,C7与其他节段外,其余各节段间的差异均无统计学意义 (均P>0.05)。3)C3~C7左右两侧纵向椎弓根-同侧椎板角分别为77.7°±7.6°,77.0°±7.1°,85.3°±8.4°,94.1°±2.2°,94.9°±3.8° 和78.5°±7.1°,76.2°±6.2°,86.4°±6.4°,94.0°±2.7°,95.6°±3.8°,呈逐渐增大趋势,C3~C4的夹角均小于90°,C5的夹角变异 较大,C6~C7的夹角均大于90°。除了C3与C4,C6与C7外,其余各节段间的差异均有统计学意义(均P<0.05)。以上指标 每节段左右两侧比较,差异均无统计学意义(均P>0.05)。结论：下颈椎椎弓根轴线与椎板平面存在一定的角度关系, 可为临床确定椎弓根螺钉的进钉角度提供参考。     

咬合重建对改善咀嚼功能和面容美观的影响

目的：探讨牙列缺损、缺失及重度磨耗患者咬合重建治疗对改善其咀嚼功能和面容美观的影响。方法：回顾临床牙列重度磨耗、牙列缺损或缺失40例病例,采用固定修复或固定活动联合修复方法实施咬合重建。咬合重建前确定治疗计划,余留牙进行完善的牙髓、牙周治疗;确定颌位关系后戴用过渡性垫3个月后固定义齿或固定活动联合修复。通过系列治疗恢复正常的垂直距离、曲线、平面,重建良好稳定的咬合关系。结果：咬合重建治疗后患者外形容貌、发音、咀嚼效能主观评价良好,咬合关系和颞下颌关节紊乱症状有显著改善。结论：采用固定修复或固定活动联合修复方法治疗牙列重度磨耗,牙列缺损或缺失,进行咬合重建的效果令人满意。详尽的治疗计划、正确的颌位关系确定、过渡性义齿戴用是固定修复咬合重建成功的关键。     

玻璃离子垫矫治安氏Ⅱ类2分类错的临床研究

目的：探讨后牙玻璃离子垫配合固定矫治器矫治安氏Ⅱ类2分类错打开咬合的机制及临床使用要点。方法：选择安氏Ⅱ类2分类错患者30例,实验组15例采用后牙玻璃离子垫加固定矫治器,对照组15名采用上颌前牙平面导板加固定矫治器。X线头影测量分析比较患者矫治前后的变化。结果：X线头影测量结果分析显示实验组和对照组ANS-Me（mm）、N-Me（mm）、S-Go（mm）、U6-PP（mm）、L6-MP（mm）、U1/SN（°）、L1/MP（°）增大,而U1-PP（mm）、U1/L1（°）、Overbite（mm）减小,差异均有统计学意义,说明前后面高增加,上下后牙伸长,上前牙压低,上下前牙唇倾。两组相比,除U1/SN、L1/MP、U1/L1外其余指标均无明显差异。结论：后牙玻璃离子垫配合固定矫治器是治疗氏Ⅱ类2分类错简单有效的方法。     

Breakthrough in three-dimensional scoliosis diagnosis: significance of horizontal plane view and vertebra vectors

Scoliosis is a multifactorial three-dimensional (3D) spinal deformity with integral and directly related vertebral deviations in the coronal, sagittal and horizontal planes. Current classification and diagnostic methods rely on two-dimensional (2D) frontal and lateral X-ray images; no routine methods are available for the visualization and quantitative evaluation of deviations in the horizontal plane. The EOS 2D/3D system presented here is a new, low-dose, orthopedic radiodiagnostic device based on Nobel prize-winning X-ray detection technology with special software for 3D surface reconstruction capabilities that finally led to a breakthrough in scoliosis diagnosis with high-quality, realistic 3D visualization and accurate quantitative parametric analysis. A new concept introducing vertebra vectors and vertebra vector parametric calculations is introduced that furnishes simplified visual and intelligible mathematical information facilitating interpretation of EOS 2D/3D data, especially with regard to the horizontal plane top view images. The concept is demonstrated by a reported scoliotic case that was readily characterized through information derived from vertebra vectors alone, supplemented with the current angulation measurement methods in the coronal and sagittal planes and axial vertebral rotation measurements in the horizontal plane, with a calibrated 3D coordinate system suitable for inter-individual comparisons. The new concept of vertebra vectors may serve as a basis for a truly 3D classification of scoliosis.     

Sagittal balance of thoracic lordoscoliosis: anterior dual rod instrumentation versus posterior pedicle screw fixation

Posterior pedicle screw fixation is now the standard treatment for surgical correction of idiopathic scoliosis and has largely replaced anterior techniques, but there have been reports describing a lordogenic effect of segmental pedicle screw instrumentation in the thoracic spine. This clinical study compared anterior dual rod instrumentation with posterior pedicle screw fixation for idiopathic thoracic lordoscoliosis, including 42 patients (7 male, 35 female; average age 16 years, range 12–34) who underwent posterior pedicle screw fixation (n = 20) or anterior dual rod instrumentation (n = 22) at two centers. The average follow-up period was 33 months (24–108 months). Inclusion criteria were a diagnosis of adolescent idiopathic scoliosis with a structural thoracic curve (Lenke 1–3) and thoracic hypokyphosis (T4–T12 < 20°). The main thoracic curve magnitude and sagittal profile on standing radiographs were evaluated. Thoracic kyphosis was significantly restored from preoperatively 10.2° to 23.4° postoperatively in the anterior group and from 7.6° to 12.9° in the posterior group (P < 0.005). Kyphosis improved significantly better in the anterior group than in the posterior group (P < 0.005). The preoperative and postoperative main thoracic curve values were 63° (48–80°) and 25.2° in the anterior group and 60.6° (50–88°) and 23.6° in the posterior group, with no significant differences between the groups. No neurological or other severe complications were observed. Anterior dual rod instrumentation in patients with thoracic lordoscoliosis allows significantly better restoration of thoracic kyphosis than posterior pedicle screw instrumentation.     

平面导板在深覆(牙合)矫治中的临床应用研究

目的：探讨平面导板矫治重度深覆[牙合]患者的作用机制及临床作用要点。方法：对18名生长发育期的重度深覆[牙合]患者,用平面导板来打开咬合,并对咬合打开前后的硬软组织变化进行分析。结果：①上下后牙及牙槽高度均增加,下后牙及牙槽高度的增加值大于上后牙及牙槽高度的增加值,而对前牙及牙槽高度的影响无统计学差异;②上下颌骨在水平方向上无改变,但下颌平面角与下面高/全面高治疗后较治疗前增大,后面高/前面高治疗后较治疗前减小;③覆[牙合]减小,Spee氏曲线得到整平;④松弛的下唇肌肉得到紧张,从而改善了侧貌外形。结论：平面导板使覆[牙合]减小主要是后牙及后牙齿槽突高度增加的结果,对生长发育期的低角重度深覆[牙合]患者治疗效果较好。