数字化设计与3D打印在自体牙移植术的应用

目的探讨术前数字化设计结合3D打印供体牙模型及受区牙槽窝模型辅助自体牙移植术的效果。方法收集12例因牙折或牙槽骨广泛吸收而无法保留的第一或第二磨牙,将其锥形束CT数据导入Mimics数字化设计软件中,选取匹配度最高的第三磨牙作为供体牙,3D打印出供体牙及受区牙槽窝模型进行术前模拟移植术。术中在供体牙模型引导下进行受区牙槽窝及供体牙的预备,将供体牙移植于受区。术后3、6、12个月复查锥形束CT评估骨重建及牙周膜状况。结果 12例患者均选择根尖孔已完全闭合的第三磨牙作为供体牙即刻移植于磨牙区。7例受区牙槽窝术前存在感染,其中1例因受区患牙感染致牙槽骨广泛吸收。12例手术短期恢复良好,均完成12个月以上随访,其中11例移植牙成功,能正常行使咀嚼功能,1例在术后14个月时出现牙根吸收。结论数字化设计结合3D打印技术能够辅助匹配最合适的供体牙,术前完成受区牙槽窝精准预备,减少供体牙在体外的暴露时间和移植到牙槽窝内的试放次数,有助于自体牙移植成功。     

Microstructure and Electrochemical Behavior of a 3D-Printed Ti-6Al-4V Alloy

3D printing (or more formally called additive manufacturing) has the potential to revolutionize the way objects are manufactured, ranging from critical applications such as aerospace components to medical devices, making the materials stronger, lighter and more durable than those manufactured via conventional methods. While the mechanical properties of Ti-6Al-4V parts manufactured with two major 3D printing techniques: selective laser melting (SLM) and electron beam melting (EBM), have been reported, it is unknown if the corrosion resistance of the 3D-printed parts is comparable to that of the alloy made with isothermal forging (ISF). The aim of this study was to identify the corrosion resistance and mechanisms of Ti-6Al-4V alloy manufactured by SLM, EBM and ISF via electrochemical corrosion tests in 3.5% NaCl solution, focusing on the effect of microstructures. It was observed that the equiaxed α + β microstructure in the ISF-manufactured Ti-6Al-4V alloy had a superior corrosion resistance to the acicular martensitic α′ + β and lamellar α + β microstructures of the 3D-printed samples via SLM and EBM, respectively. This was mainly due to the fact that (1) a higher amount of β phase was present in the ISF-manufactured sample, and (2) the fraction of phase interfaces was lower in the equiaxed α + β microstructure than in the acicular α′ + β and lamellar α + β microstructures, leading to fewer microgalvanic cells. The lower corrosion resistance of SLM-manufactured sample was also related to the higher strain energy and lower electrochemical potential induced by the presence of martensitic twins, resulting in faster anodic dissolution and higher corrosion rate.     

Flexural Performance of Encased Pultruded GFRP I-Beam with High Strength Concrete under Static Loading

There is an interesting potential for the use of GFRP-pultruded profiles in hybrid GFRP-concrete structural elements, either for new constructions or for the rehabilitation of existing structures. This paper provides experimental and numerical investigations on the flexural performance of reinforced concrete (RC) specimens composite with encased pultruded GFRP I-sections. Five simply supported composite beams were tested in this experimental program to investigate the static flexural behavior of encased GFRP beams with high-strength concrete. Besides, the effect of using shear studs to improve the composite interaction between the GFRP beam and concrete as well as the effect of web stiffeners of GFRP were explored. Encasing the GFRP beam with concrete enhanced the peak load by 58.3%. Using shear connectors, web stiffeners, and both improved the peak loads by 100.6%, 97.3%, and 130.8%, respectively. The GFRP beams improved ductility by 21.6% relative to the reference one without the GFRP beam. Moreover, the shear connectors, web stiffeners, and both improved ductility by 185.5%, 119.8%, and 128.4%, respectively, relative to the encased reference beam. Furthermore, a non-linear Finite Element (FE) model was developed and validated by the experimental results to conduct a parametric study to investigate the effect of the concrete compressive strength and tensile strength of the GFRP beam. The developed FE model provided good agreement with the experimental results regarding deformations and damaged patterns.     

Fatigue Life Prediction of CFRP-Strengthened RC Beams with Flexural Crack under Hygrothermal Environments

The durability of reinforced concrete (RC) beams strengthened with carbon fiber-reinforced polymer (CFRP) is a worldwide concern in structural engineering. As an important part of the strengthened beam, the performance of the CFRP–concrete interface under hygrothermal environments is a delicate problem. In this paper, the fatigue behavior of CFRP-strengthened RC beams is analyzed by a theoretical model. In the model, CFRP–concrete interface degradation under hygrothermal environments is involved. Since interface debonding and rebar fracture induced by intermediate cracking are two typical failure modes, the damage models of rebar and the CFRP–concrete interface are established. Based on the theoretical model, the failure mode of CFRP-strengthened RC beams can be predicted, and fatigue life can be determined. The results showed that IC debonding is more likely to occur under hygrothermal environments. The accurate prediction of failure modes is essential for fatigue life prediction.     

锥形束CT在鼻泪管阻塞性疾病辅助诊断中的应用价值

目的 探讨锥形束CT(CBCT)在鼻泪管阻塞性疾病辅助诊断中的应用价值.方法 选取2018年1月至2020年8月在中国人民解放军总医院眼科门诊就诊的鼻泪管阻塞性疾病患者104例,按随机数字表法分为观察组及对照组,各52例,观察组患者采用CBCT检查鼻泪管,对照组采用CT泪道造影检查鼻泪管.观察并比较两组患者鼻泪管的影像...     

应用锥形束CT对种植区牙槽骨质量分类方法的改良研究

目的 应用锥形束CT(cone beam CT,CBCT)测量种植区牙槽骨质量并结合Lekholm和Zarb分类法对骨质量分类方法进行改良,以期为提高牙槽骨质量分类的准确性提供指导。方法 选择2015年10月至2017年10月在呼和浩特市口腔医院种植科进行种植修复的196例患者术前CBCT影像资料,应用Invivo5诊断设计软件测量306个种植位点的牙槽骨皮质骨厚度和松质骨密度（皮质骨与松质骨的CT值差值）,以Lekholm和Zarb分类法为基础结合测量数据对骨质量进行改良后的量化分类。结果 牙槽骨皮质骨厚度为0.18～2.89 mm,中位数为0.92 mm。皮质骨与松质骨的CT值差值为88.5～667.8 HU,应用百分位数法找到33.3%和66.6%对应的数值分别为297.8 HU和356.1 HU。依据此数据结合Lekholm和Zarb分类法将196例患者的306个种植位点骨质量分为4类,其中Ⅰ类骨种植位点46个（占15.0%）,Ⅱ类骨104个（占34.0%）,Ⅲ类骨114个（占37.3%）,Ⅳ类骨42个（占13.7%）。结论 结合Lekholm和Zarb分类法,应用CBCT测量...     

两台直线加速器束流匹配后互换执行调强放疗计划的可行性研究

目的:探讨6MV X线调强放疗(IMRT)与容积调强弧形治疗(VMAT)计划在经束流匹配后,在两台医科达公司直线加速器(Versa HD和Synergy)上互换执行的可行性。方法:随机选取鼻咽癌、中心型肺癌、前列腺癌各12例患者影像,分别设计IMRT与VMAT计划,并采用电离室与ArcCheck对两台加速器6MV光子束...     

CBCT/CT与普通X线片在上颌前牙区埋伏多生牙定位的比较

目的探讨锥形束CT(CBCT)/CT与普通X线片在上颌前牙区埋伏多生牙定位检查的应用价值。方法结合临床病例,对上颌前牙区完全埋伏多生牙采用CBCT/CT与多种普通X线片定位方法进行比较和分析。结果普通X线片对埋伏多生牙的定位有一定帮助,视差定位法是比较经济和实用的定位方法。CBCT/CT检查能准确展示多生牙的三维结构,并进行相应的测量与辅助手术设计,与普通X线片比具有显著优势。结论上颌前牙区埋伏多生牙可根据医疗条件选择适合的定位检查方法,而CBCT检查将是发展的趋势。     

NSF-Based Analysis of the Structural Stressing State of Trussed Steel and a Concrete Box Girder

This paper analyses the characteristics of the mechanical behavior of a trussed steel and concrete box beam under bending conditions based on the structural stressing state theory and the numerical shape function method. Firstly, the parametric generalized strain energy density was introduced to characterize the structural stressing state of trussed steel stud concrete box girders, and the strain energy density sum was plotted. Then the Mann-Kendall criterion was used to discriminate the leap point of the curve change and to redefine the structural failure load. By analyzing the strain and displacement, the existence of a sudden change in the structural response during the load-bearing process was again demonstrated. Afterwards, the numerical shape function method was used to extend the strain data, and further in-depth analyses of strain/stress fields and internal forces were carried out to show in detail the working characteristics of each under load. Through an in-depth analysis from different angles, the rationality of updating the failure load was verified. Finally, the effects of different structure parameters on the evolution of the structural stresses of the members were analyzed in a transversal comparison. The analysis results of the stress state of a steel-concrete truss structure reveal the working behavior characteristics of a steel-concrete truss structure from a new angle, which provides a reference for the design of a steel-concrete truss structure in the future.     

Picosecond Bessel Beam Fabricated Pure,Gold-Coated Silver Nanostructures for Trace-Level Sensing of Multiple Explosives and Hazardous Molecules

A zeroth-order, non-diffracting Bessel beam, generated by picosecond laser pulses (1064 nm, 10 Hz, 30 ps) through an axicon, was utilized to perform pulse energy-dependent (12 mJ, 16 mJ, 20 mJ, 24 mJ) laser ablation of silver (Ag) substrates in air. The fabrication resulted in finger-like Ag nanostructures (NSs) in the sub-200 nm domain and obtained structures were characterized using the FESEM and AFM techniques. Subsequently, we employed those Ag NSs in surface-enhanced Raman spectroscopy (SERS) studies achieving promising sensing results towards trace-level detection of six different hazardous materials (explosive molecules of picric acid (PA) and ammonium nitrate (AN), a pesticide thiram (TH) and the dye molecules of Methylene Blue (MB), Malachite Green (MG), and Nile Blue (NB)) along with a biomolecule (hen egg white lysozyme (HEWL)). The remarkably superior plasmonic behaviour exhibited by the AgNS corresponding to 16 mJ pulse ablation energy was further explored. To accomplish a real-time application-oriented understanding, time-dependent studies were performed utilizing the AgNS prepared with 16 mJ and TH molecule by collecting the SERS data periodically for up to 120 days. The coated AgNSs were prepared with optimized gold (Au) deposition, accomplishing a much lower trace detection in the case of thiram (~50 pM compared to ~50 nM achieved prior to the coating) as well as superior EF up to ~10⁸ (~10⁶ before Au coating). Additionally, these substrates have demonstrated superior stability compared to those obtained before Au coating.