Study on Multi-density Contrast Agent Fillers of Duct Casting Based on CT Three-Dimensional Reconstruction

The three-dimensional visualization model of human body duct is based on virtual anatomical structure reconstruction with duct angiography,which realizes virtual model transferred from two-dimensional,planar and static images into three-dimensional,stereoscopic and dynamic ones repectively.In recent years,the multi-duct segmentation and division of the same specimen（or organ） is the focus of attention shared by surgeons and clinical anatomists.On the basis of 4.22 g/cm3 body bone density,this study has screened out metal oxide contract agent with different density for infusion and modeling,as well as compared and analyzed the effects of three-dimensional image of CT virtual bronchoscopy（CTVB）,three-dimensional image of CT maximum intensity projection and three-dimensional model.This experiment result showed synchronously infusing multi-duct of same specimen（or organ） with contrast agent in different densities could reconstruct three-dimensional models of all ducts once only and adjust threshold to develop single or multiple ducts.It was easier to segment and observe the duct structure,anastomosis,directions and crossing in different parts,which was beyond comparison with three-dimensional image of CTVB.Although the existing three-dimensional duct reconstruction techniques still cannot be applied in living bodies temporarily,this study focused on a creative design of ducts segmentation in different density,which proposed a new experimental idea for developing multi-duct three-dimensional model in living body in the future.It will play a significant role in disease diagnosis and individual design in surgical treatment program.Therefore,this study observes the three-dimensional status of human duct with the application of contrast agent fillers in different density,combined with three-dimensional reconstruction technology.It provides an innovative idea and method for constructing three-dimensional model of digital multi-duct specimen,and the ultimate goal is to develop the digitized virtual human and precise medical treatment better and faster.

Application of dental stem cells in three-dimensional tissue regeneration

Dental stem cells can differentiate into different types of cells.Dental pulp stem cells,stem cells from human exfoliated deciduous teeth,periodontal ligament stem cells,stem cells from apical papilla,and dental follicle progenitor cells are five different types of dental stem cells that have been identified during different stages of tooth development.The availability of dental stem cells from discarded or removed teeth makes them promising candidates for tissue engineering.In recent years,three-dimensional(3D)tissue scaffolds have been used to reconstruct and restore different anatomical defects.With rapid advances in 3D tissue engineering,dental stem cells have been used in the regeneration of 3D engineered tissue.This review presents an overview of different types of dental stem cells used in 3D tissue regeneration,which are currently the most common type of stem cells used to treat human tissue conditions.

Evaluation of three-dimensional biofilms on antibacterial bonding agents containing novel quaternary ammonium methacrylates

Antibacterial adhesives are promising to inhibit biofilms and secondary caries. The objectives of this study were to synthesize and incorporate quaternary ammonium methacrylates into adhesives, and investigate the alkyl chain length effects on three-dimensional biofilms adherent on adhesives for the first time. Six quaternary ammonium methacrylates with chain lengths of 3, 6, 9, 12, 16 and 18 were synthesized and incorporated into Scotchbond Multi-Purpose. Streptococcus mutans bacteria were cultured on resin to form biofilms. Confocal laser scanning microscopy was used to measure biofilm thickness, live/dead volumes and live-bacteria percentage vs. distance from resin surface. Biofilm thickness was the greatest for Scotchbond control; it decreased with increasing chain length, reaching a minimum at chain length 16. Live-biofilm volume had a similar trend. Dead-biofilm volume increased with increasing chain length. The adhesive with chain length 9 had 37% live bacteria near resin surface, but close to 100% live bacteria in the biofilm top section. For chain length 16, there were nearly 0% live bacteria throughout the three-dimensional biofilm. In conclusion, strong antibacterial activity was achieved by adding quaternary ammonium into adhesive, with biofilm thickness and live-biofilm volume decreasing as chain length was increased from 3 to 16. Antibacterial adhesives typically only inhibited bacteria close to its surface; however, adhesive with chain length 16 had mostly dead bacteria in the entire three-dimensional biofilm. Antibacterial adhesive with chain length 16 is promising to inhibit biofilms at the margins and combat secondary caries.

Electrochemical behavior of Co-Cr and Ni-Cr dental cast alloys

The cast structures influencing the electrochemical corrosion behavior of Co-Cr and Ni-Cr dental alloys were studied using potentiodynamic polarization and AC impedance in 0.9% (mass fraction) NaCl solution at (37±1) ℃. The phase and microstructure of the alloys that were fabricated using two different casting methods viz. centrifugal casting and high frequency induction casting, were examined using X-ray diffraction analysis, scanning electron microscopy and energy dispersive spectroscopy. The roles of alloying elements and the passive film homogeneity on the corrosion resistance of Co-Cr-Mo and Ni-Cr-Mo dental cast alloys were reviewed. The results of electrochemical study show that the dependence of corrosion resistance on the microstructure associated with the casting methods is marginal. The Co-Cr alloy exhibits more desirable corrosion resistance properties than the Ni-Cr alloy. There is severe preferential dissolution of Ni-rich, Cr and Mo depleted zones in the Ni-Cr alloy.

Characteristics and distribution of microstructures in high pressure die cast alloys with X-ray microtomography:A review

Al and Mg alloy high pressure die castings(HPDC)are increasingly used in automotive industries.The microstructures in the castings have decisive effect on the casting mechanical properties,in which the microstructure characteristics are fundamental for the investigation of the microstructure-property relation.During the past decade,the microstructure characteristics of HPDC Al and Mg alloys,especially micro-pores andα-Fe,have been investigated from two-dimensional(2D)to threedimensional with X-ray micro-computed tomography(μ-CT).This paper provides an overview of the current understanding regarding the 3D characteristics and formation mechanisms of microstructures in HPDC alloys,their spatial distributions,and the impact on mechanical properties.Additionally,it outlines future research directions for the formation and control of heterogeneous microstructures in HPDC alloys.

Solidification of Be-free Ni-based dental alloy

A novel, Nb- and Si-rich and Be-free Ni-based alloy was cast by two methods of investment casting and continuouscasting to study the microstructure evolution during solidification and its mechanical properties. The solidification of the alloy startedwith the primary crystallization of FCC-γ, followed by a binary eutectic reaction, with the formation of a heterogeneous constituent：FCC-γ＋G-phase, which replaced the low-melting eutectic （FCC-γ＋NiBe） in the Be-bearing alloys. AlNi6Si3 and γ′ formed during theterminal stages of solidification by investment casting, while the formation of AlNi6Si3 was suppressed by continuous casting. TheScheil solidification model agreed very well with the experimental results.

Morphological Features of Complex Congenital Cardiovascular Anomalies in Fetuses:as Evaluated by Cast Models

Accurate prenatal diagnosis of complex congenital cardiovascular anomalies, vascular ones in particular, is still challenging. A fetal cardiovascular cast model can provide a copy of the cardiac chambers and great vessels with normal or pathological structures. This study was aimed to demonstrate three-dimensional anatomy of complex congenital cardiovascular anomalies in fetuses by means of corrosion casting. Twenty fetuses with prenatal-ultrasound-diagnosed complex cardiovascular anomalies were enrolled in this study（19 to 35 gestational weeks）. Fetal cardiovascular cast models were made by a corrosion casting technique. The specimens were injected with casting material via the umbilical vein, and then immersed in strong acid after casting fluid was solidified, to disclose the geometries of cardiovascular cavities. Nineteen cast models were successfully made from 20 specimens. The casts distinctly showed the morphological malformations and spatial relationship between cardiac chambers and great vessels. One hundred and eleven abnormalities were revealed by casting in the 19 specimens, including 34 abnormalities located in the cardiac chambers（3, 4 and 27 anomalies in the atria, atrioventricular valves and ventricles, respectively）, and 77 in the great vessels（28, 20, 24 and 5 anomalies in the aorta and its branches, the pulmonary artery, the ductus arteriosus and the major veins, respectively）. Corrosion casting can display three-dimensional anatomy of fetal complex cardiovascular anomalies. This improves our understanding of related pathomorphology and prenatal diagnosis.

Diagnosis of Dental Caries Using Terahertz Technology

Recently,the diagnoses of dental caries and other dental issues are in a queue as only X-ray-based techniques are available in most hospitals around the world.Terahertz(THz)parametric imaging(TPI)is the latest technology that can be applied for medical applications,especially dental caries.This technology is harmless and thus suitable for biological samples owing to the low energy of THz emission.In this paper,a developed TPI system is used to investigate the two-dimensional(2 D)and three-dimensional(3D)images of different samples from human teeth.After analyzing the measured images of human teeth,the results suggest that the THz parametric technology is capable of investigating the inner side structure of the teeth.This technique can be useful in detecting the defects in all types of human and animal teeth.The measurement and analytical calculations have been performed by using the TPI system and MATLAB,respectively,and both are in good agreement.The characteristics of THz waves and their interactions with the tooth samples are summarized.And the available THz-based technologies,such as TPI,and their potential applications of diagnoses are also presented.

一种新型三维牙颌模型激光扫描仪可靠性对比研究

目的 :检验新型三维牙颌模型激光扫描仪的可靠性。方法 :分次利用不同方法 ,扫描和测量 8副牙列石膏模型上的解剖标志点 ,对测量结果进行统计分析。结果 :同一激光扫描两次定点的线距和角度的测量结果之间差异没有显著性 ;两次激光扫描分别定点测量的线距和角度结果之间差异也没有显著性 ;激光扫描定点测量和三维测量仪分别测得的线距和角度结果之间差异也没有统计学意义。结论 :D .0 2 L 3DSCANNER激光扫描仪具有较高的精度 ,较好的可靠性 ,扫描速度快 ,扫描盲区少 ,该系统可以用于以后修复体CAD

高频离心铸造过程中金属液体最佳铸入角度的研究

目的 :探讨高频离心铸造过程中金属液体最佳铸入角度。方法 :采用螺纹型试件 ,测量不同铸入角度试件的铸入率。结果 :铸入角度 45°～ 60°时试件的铸流率高。结论 :高频离心铸造过程中金属液体最佳铸入角度为 45°～

Ti-75铸造后机械性能测试的研究

目的：研究及比较Ｔｉ－７５金属在牙科铸造后的机械性能。方法：利用Ｉｎｓｔｒｏｎ拉伸试验机，对Ｔｉ－７５金属牙科铸造后部分力学性能进行了测试研究，并与Ｔｉ－６Ａｌ－４Ｖ及临床常用钴铬合金进行了比较。结果：Ｔｉ－７５铸造后抗拉强度为８５６．７ＭＰａ，屈服强度为５４０ＭＰａ延伸率为７．３％。Ｔｉ－６Ａｌ－４Ｖ铸造后抗拉强度为９５６．７ＭＰａ，屈服强度为５９０ＭＰａ，延伸率为５．２％。Ｃｏ－Ｃｒ合金铸造后抗拉强度为６５１．２ＭＰａ，屈服强度为４７８．８ＭＰａ，延伸率为６．１％。结论：Ｔｉ－７５金属铸造后抗拉强度，屈服强度及延伸率等性能指标均优于钴铬合金，延伸率也高于Ｔｉ－６Ａｌ－４Ｖ合金。

三轴牙颌模型三维激光扫描测量分析系统的研制

目的 研制开发具有三轴运动结构的牙颌模型三维激光扫描测量分析系统。方法运用三个步进电机构成牙颌模型双轴旋转与单向平移的运动,应用点状光束与线阵列摄像机(CCD)构成非接触式高精度纵向位移检测器获取牙颌模型的三维数据,在windows环境下完成牙颌模型的三维重建、测量。结果 系统的扫描精度为0.01 mm,平均测量误差<0.1 mm。采用定制标定块进行了标定实验。用本系统与机械法对20副正常模型进行了测量比较,两者之间差异无显著性(P>0.05)。结论 该系统具有测量精确,高效和没有盲区的优点。

牙用Ti-75合金铸造性能研究

采用国产牙科专用铸钛机对Ｔｉ７５合金做为牙科修复材料的可行性进行了研究。结果表明：Ｔｉ７５合金铸流率（ＣＶ）可达９８％；铸造后抗拉强度为８５０ＭＰａ，屈服强度为７７５ＭＰａ，延伸率为７％；铸件金相组织呈板条状α加少量β，表层结构与内部结构不同。对表层结构进行显微硬度测试，由表层向中心部显微硬度逐渐降低，反应层厚约４０μｍ。经ＳＥＭ观察Ｔｉ７５合金表面反应层可分为４层，主要元素为Ｚｒ，Ａｌ，Ｏ，Ｓｉ。去除表面反应层仍能满足义齿精度的要求。

牙模型视频立体测量系统的建立与应用

目的 建立计算机辅助的牙颌模型立体分析测量系统并应用于临床。方法 将视频测量技术应用于口腔医学领域 ,系统由坐标控制场、两台CCD彩色摄像机、真彩色图象卡、高清晰度彩色监视器及计算机等设备组成 ,通过特定的测量软件完成模型测量分析。结果 系统经检测精度合乎临床要求 ,并应用本系统分别对正常牙合、安氏Ⅱ类 1分类错牙合及安氏Ⅲ类错牙合的模型进行了研究。

2种牙科贵金属铸造合金的细胞毒性研究

采用四甲基偶氮唑盐微量酶反应比色法(MTT法)对自行研制的2种Au-Ag-Pd-Cu牙科铸造合金的细胞毒性进行了研究。并用相差显微镜对细胞形态进行了观察分析。试验使用的细胞株为小鼠结缔组织成纤维细胞(L-929),培养液为含5％小牛血清(FBS)的RPMI1640。结果表明:细胞在2种Au-Ag-Pd-Cu牙科铸造合金的浸渍液中培养3d和5d后,细胞形态良好,生长旺盛;2种合金的细胞毒性级别为0～1级,具有良好的细胞相容性。

大年龄未手术腭裂患者上颌牙弓形态发育的研究

目的 :探讨影响上颌牙弓生长发育的因素。方法 :对 2 0例未手术腭裂患者的牙颌模型进行测量 ,并与 2 0名正常成人作对照分析。结果 :大年龄未手术腭裂患者与正常成人在尖牙区宽度存在显著性差异 (P <0 0 5 )。而上颌深度及后牙区的宽度无显著性差异 (P >0 0 5 )。结论 :在腭裂组 ,畸形的存在主要是在切牙区及尖牙区 ,对后牙区横向和垂直向的影响较小。

牙颌模型三维激光扫描系统可靠性研究及与手工测量的比较

目的 对牙颌模型三维激光扫描系统的可靠性进行研究 ,并为其临床应用提供科学依据。方法 利用D .0 1-L - 3DSCANNER系统扫描和测量了 30例基本正常石膏模型。采用三种方法检验了牙颌模型三维激光扫描系统的可靠性 ,并与手工测量进行了比较。结果 可靠性研究三个方法的结果显示无显著性差异 ;与手工测量的比较无显著性差异 ,但牙颌模型三维激光扫描系统具有一些手工测量所无法达到的功能。结论 牙颌模型三维激光扫描系统可靠性强 ,稳定性好 ,可应用于临床、科研。

牙科铸钛技术的研究现状

对目前牙科铸钛系统 ,包埋材料 ,铸件表面反应层结构以及铸造工艺如铸模温度、铸造压力等的研究及发展现状进行了综合介绍。

三种方法制作的Plat-Ⅱ型铸造陶瓷全冠适合性的比较

【目的】探讨改善Plat Ⅱ型铸造陶瓷全冠适合性的方法。【方法】分别用常规脱模铸造法、代型隙料法、带模铸造法制作Plat Ⅱ型铸造陶瓷全冠 2 4个 ,用磷酸锌粘固粉粘固于各自的代型上 ,测试各组冠 ,各个部位的粘固剂厚度 ,比较其适合性。【结果】 3种方法制作的全冠其粘固剂平均厚度分别为 :5 2 μm、42 μm、30 μm ,边缘浮升量分别为 :6 3μm、5 9μm、42μm。 3种方法制作的全冠边缘浮升量、轴壁、牙合面粘固剂厚度均有显著性差异 (P <0 0 1)。【结论】用代型隙料法和带模铸造法制作的Plat

高嵌体修复大面积缺损活髓牙的临床观察

目的:比较贵金属合金烤瓷高嵌体与铸造高嵌体,对牙体组织大面积缺损活髓牙的修复效果。方法:使用随机数表将65例患者的76颗患牙编号分组,分别给予贵金属合金的烤瓷高嵌体与铸造高嵌体治疗。使用玻璃离子水门汀粘结。所有操作均由1名医生独立完成。根据修改的USPHS标准,在治疗后1周及1年时,由两位医师独立对两组治疗的术后敏感性、继发龋、边缘变色、肩台适合性、高嵌体折裂等指标作评判。卡方检验和/或秩和检验统计数据。结果:治疗后1周时,两组在美观上存在显著性差异(P<0.05),其他各指标不存在显著性差异。戴牙1年后,高嵌体折裂、美观两指标两组存在显著性差异(P<0.05),其他各指标均不存在显著性差异。结论:高嵌体是针对大面积缺损活髓牙的一种有效、安全的治疗,总体而言两种类型都可以接受,烤瓷高嵌体更具有美学优势。