Development of an In-Situ Laser Machining System Using a Three-Dimensional Galvanometer Scanner

In this study, a three-dimensional (3D) in-situ laser machining system integrating laser measurement and machining was built using a 3D galvanometer scanner equipped with a side-axis industrial camera. A line structured light measurement model based on a galvanometer scanner was proposed to obtain the 3D information of the workpiece. A height calibration method was proposed to further ensure measurement accuracy, so as to achieve accurate laser focusing. In-situ machining software was developed to realize time-saving and labor-saving 3D laser processing. The feasibility and practicability of this in-situ laser machining system were verified using specific cases. In comparison with the conventional line structured light measurement method, the proposed methods do not require light plane calibration, and do not need additional motion axes for 3D reconstruction;thus they provide technical and cost advantages. The insitu laser machining system realizes a simple operation process by integrating measurement and machining,which greatly reduces labor and time costs.

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.

Three-dimensional atomic force microscopy based on tailored cantilever probe with flared tip

In order to meet the requirements of nondestructive testing of true 3D topography of micro-nano structures,a novel three-dimensional atomic force microscope(3D-AFM)based on flared tip is developed.A high-precision scanning platform is designed to achieve fast servo through moving probe and sample simultaneously,and several combined nanopositioning stages are used to guarantee linearity and orthogonality of displacement.To eliminate the signal deviation caused by AFM-head movement,a traceable optical lever system is designed for cantilever deformation detection.In addition,a method of tailoring the cantilever of commercial probe with flared tip is proposed to reduce the lateral force applied on the tip in measurement.The tailored probe is mounted on the 3D-AFM,and 3D imaging experiments are conducted on different samples by use of adaptive-angle scanning strategy.The results show the roob-mean-square value of the vertical displacement noise(RMS)of the prototype is less than 0.1 nm and the high/width measurement repeatability(peak-to-peak)is less than 2.5 nm.

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.

Wind dynamic environment and wind-sand erosion and deposition processes on different surfaces along the Dunhuang–Golmud railway,China

The Dunhuang–Golmud railway passes through different deserts in arid areas,especially drifting-sand desert and sandy-gravel Gobi.The near-surface wind environment and wind-sand transport process vary due to different external factors,such as topography,vegetation,and regional climate,resulting in evident spatial differences in surface erosion and deposition.Consequently,the measures for preventing wind-sand hazards will differ.However,the mechanism and control theory of sand damage remain poorly understood.In this study,we used meteorological observation,three-dimensional(3D)laser scanning,and grain-size analysis to compare and evaluate the spatial distribution of wind conditions,sand erosion and deposition patterns,and grain composition in the drifting-sand desert and sandy-gravel Gobi along the Dunhuang–Golmud railway in China.Results show that the annual mean wind speed,the frequency of sand-driving wind,and the drift potential of sandy-gravel Gobi are higher than those of drifting-sand desert,indicating a greater wind strength in the sandy-gravel Gobi,which exhibits spatial heterogeneity in wind conditions.The major sediment components in sandy-gravel Gobi are very fine sand,fine sand,and medium sand,and that in drifting-sand desert are very fine sand and fine sand.We found that the sediment in the sandy-gravel Gobi is coarser than that in the drifting-sand desert based on mean grain size and sediment component.The spatial distributions of sand erosion and deposition in the sandy-gravel Gobi and drifting-sand desert are consistent,with sand deposition mainly on the west side of the railway and sand erosion on the east side of the railway.The area of sand deposition in the drifting-sand desert accounts for 75.83%of the total area,with a mean deposition thickness of 0.032 m;while the area of sand deposition in the sandy-gravel Gobi accounts for 65.31%of the total area,with a mean deposition thickness of 0.028 m,indicating greater deposition amounts in the drifting-sand desert due to the presence of more fine sediment components.However,the sand deposition is more concentrated with a greater thickness on the embankment and track in the sandy-gravel Gobi and is dispersed with a uniform thickness in the drifting-sand desert.The sand deposition on the track of the sandy-gravel Gobi mainly comes from the east side of the railway.The results of this study are helpful in developing the preventive measures and determining appropriate selection and layout measures for sand control.

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

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。

标准牙冠三维模型的建立及其可操作平台的研究

目的 建立标准牙冠的计算机三维模型以及开发其可操作的软件平台。方法 利用三维激光扫描仪扫描全牙列 2 8颗标准牙冠的石膏模型 ,编写程序对获得的数据进行处理 ,重建各牙冠的三维图形 ,并结合国人牙冠的平均测量数据对其进行调整 ,同时在牙冠表面定义特征区和特征点 ,利用程序对牙冠进行各种变换和调整。结果 扫描仪获取了牙冠数据 ,系统重建了各牙冠的标准三维图形 ,可对牙冠进行各种变换使其产生位移、旋转和整体形变 ,按照各牙冠的解剖特点及正中牙合时的咬合接触定义了特征区 ,特征区可以在空间三个方向上产生指定形变。结论 标准牙冠的三维计算机模型精确可靠 ,其操作平台实现了多种功能 ,为进一步开发打下了基础。

国产三轴牙颌模型扫描仪的一种标定方法

目的建立国产牙颌模型三维扫描仪的标定方法,并对标定结果进行检验。方法设计专用定制的带有量化指标的标准块,对其采集三维数据后用最小二乘法对数据进行拟合,从而获得系统参数。标定完成后分别与手工测量和机械式三坐标测量仪(YM - 2 115 )进行了牙颌模型测量的相关对比实验。结果实验结果显示经标定完成后对牙颌模型测量结果与手工测量和机械式三坐标测量仪的测量结果没有显著性差异,初步验证了该标定方法的可行性。结论研究表明该标定方法简便、准确,可以作为一种常规方法对国产D .0 2 -L - 3DSCANNER牙颌模型扫描仪进行日常维护性标定。

口内数字印模技术

口内数字印模技术是近年来口腔医学关注的焦点之一。与模型数字印模技术相比,口内数字印模技术具有方便、快捷、实时、灵活等特点,可大大提高患者就诊的舒适度,具有明显的技术优势。与此同时,口内光学印模技术也面临着口腔复杂扫描环境的严峻挑战,亟待解决若干光学扫描瓶颈问题的局限,寻求扫描精度上的新突破。本文详细列举口内数字印模技术的优势与局限性,阐述分析其临床适应证,用以指导临床应用;对主流技术的原理介绍和临床应用的现状介绍,可让读者对口内数字印模技术有较全面的认识和了解。

数字化技术在口腔种植修复中的应用

随着计算机技术的飞速发展及其在口腔医学领域的广泛应用,当代口腔种植诊疗模式发生了前所未有的改变。数字化技术已真正渗透到种植修复治疗中的每一个环节,实现了精准、高效、舒适的个性化口腔种植诊疗新模式。该文旨在详细介绍口腔种植学中数字化技术的临床应用现状,阐述分析其优势与局限,并对其未来的发展方向进行探讨与展望。

浅谈口腔三维扫描仪招标采购中技术参数的制定

目的:探讨招标采购口腔三维扫描仪的关键技术要求,使技术要求制定得更加科学合理。方法:通过对目前主流的口腔三维扫描仪技术参数的对比分析,探讨招标采购口腔三维扫描仪时制定的关键技术要求。结果:口腔三维扫描仪的关键技术要求有扫描对象、适应证、扫描精度、扫描效率、数据接口、软件功能等。结论:在口腔三维扫描仪采购中,要根据口腔医学专业领域、扫描对象、用途等综合因素来制定技术要求,才能顺利采购到合适的设备。

基于口内扫描仪和种植模板的数字化全口覆盖义齿的临床应用

目的:探讨基于口内扫描仪和种植模板的数字化全口覆盖义齿的临床应用。方法:将2017年1月~2019年12月在我院口腔修复科进行治疗的牙列缺失患者64例随机分为对照组和实验组。对照组采用传统全口义齿修复法,实验组采用基于口内扫描仪和种植模板的数字化全口覆盖义齿修复。比较两组患者种植体成功率、种植体周围边缘骨吸收、种植体位置偏移以及义齿满意度的差异。结果:实验组患者种植成功率显著高于对照组,种植体周围边缘骨吸收低于对照组,实验组患者种植体肩部偏移、根部偏移、角度偏移、深度偏移均低于对照组,患者咀嚼功能、固定功能、舒适程度满意度均高于对照组,差异均具有统计学意义(P<0.05)。结论:基于口内扫描仪和种植模板的数字化全口覆盖义齿应用于牙列缺失患者,能够提高患者种植成功率,降低种植体周围边缘骨吸收、种植体位置偏移,改善患者义齿满意度,具有较高的临床应用价值。

基于相机阵列的新型牙科三维扫描仪

为解决传统牙科三维扫描仪扫描中的抖动问题,提出了一种基于相机阵列的新型牙科三维扫描仪。利用多个不同视场的相机可以直接单次照相获取目标的三维信息,避免了扫描过程中抖动带来的影响,提高系统实时性。由于牙齿尺寸较小,所以选择微透镜阵列代替大型相机阵列,在减小系统体积的同时可以更好地保证相机间光轴的平行度。实验结果显示,系统最终实现了单颗牙齿的视差和深度计算。系统结构简单,便于小型化和低成本口内牙齿三维测量设备的研制,进一步推进医学数据的数字化进程。

数字化印模在口腔种植修复中的研究进展

数字化印模是指使用口内扫描仪在患者口内无需直接接触即获取组织图像,并合成三维牙列影像的印模技术。数字化印模于口腔种植修复中的应用近年来开始受到关注,但其印模精度尚不明确,尤其是多颗种植体的数字化印模精度。本文详细介绍数字化印模的原理、在种植修复不同类型牙列缺损或缺失情况下的精度以及影响精度的相关因素,以期为数字化印模在种植修复中的临床应用提供参考依据。

两种数字化咬合导板颌骨定位精度比较研究

目的对比研究数字化咬合导板的设计和制作方法,提高数字化咬合导板的颌骨定位精度。方法通过扫描口内天然牙列与体外石膏模型两种方法获取两组数字化牙模型,将数字化牙[牙合]模型导入Mimics Medical 20.0软件,进行咬合导板设计及3D打印制作,术中导航记录两组咬合导板定位颌骨的标记点坐标,计算7个颌骨测量点与设计方案数据间的距离偏差(DE)。应用咬合导板的适应性、偏差分析中的指标均方根值(RMS)、术中导航数据综合评价两组咬合导板的精度。结果两组咬合导板口内适应性比较差异具有统计学意义(χ^2=22.308,P<0.01)。两组咬合导板RMS比较差异有统计学意义(t=2.086,P<0.05)。两组咬合导板在上下颌导航X轴上A点和Y轴上A、FPR、FPL、RPR、RPL点与设计方案数据间的DE比较差异具有统计学意义(Z=-2.871^-2.020,P<0.05)。结论口扫咬合导板的定位精度优于模扫咬合导板。

新型小型化牙科扫描仪探头的光学系统设计

为解决牙科扫描探头小型化问题,基于结构光三维重建算法,创新性地设计出一种投影与成像共孔径设置的小型化牙科三维扫描仪探头光学系统。系统采用分视场共孔径技术,部分视场用于实现投影功能,另一部分视场用于实现成像功能,投影区域和成像区域存在公共区域。仿真实验给出了在扫描范围为46×35mm2内的系统性能,借助LightTools软件做了照明分析仿真,证明了系统光路的可行性。

口腔种植体植入精度评估方法的应用进展

静态导板、动态导航与口腔种植机器人等数字化技术在口腔种植领域的应用实现了精准种植的目的,然而口腔种植位点精准记录与评估尚无统一标准,因此选择高精度术后评估方法来准确反映种植体精度变得尤为重要。目前口腔种植体植入术后评估常用的仪器有CBCT、口内扫描仪、台式光学扫描仪、三坐标测量仪等。在其他领域的钻孔实验中,也有使用卡尺、塞规、数字化测量仪器如三坐标测量仪与激光跟踪仪等方法进行测量,这些方法可以为口腔种植体植入精度的评估提供参考。本文将对口腔种植钻孔实验中所涉及的精度评估方法的原理、精度以及特点进行综述,为实验与临床中种植体植入精度评估提供理论参考。

替牙期62例上颌尖牙阻生儿童牙弓及腭部形态特征分析

目的:比较上颌尖牙阻生与无阻生儿童牙弓及腭部形态的差异,为上颌尖牙阻生早期识别和干预提供参考。方法:选择8~11岁[平均(9.82±1.04)岁]儿童62例,分为实验组(上颌尖牙阻生)和对照组(无上颌尖牙阻生),每组31例。将2组患者石膏模型通过3D激光扫描后转化为数字模型,测量牙弓宽度、牙弓长度、基骨宽度、腭部宽度、腭部高度、腭部体积、表面积。采用SPSS 24.0软件包对实验数据进行配对t检验。结果:实验组儿童牙弓与腭部宽度相比对照组更窄(P<0.05),但2组儿童在牙弓长度、基骨宽度、腭部高度方面无显著差异(P>0.05)。对照组儿童腭部体积、表面积显著大于实验组(P<0.05)。结论:替牙期上颌尖牙阻生儿童牙弓宽度、腭部宽度、腭部体积、表面积均小于对照组。早期诊断上颌尖牙阻生时,牙弓宽度、腭部宽度、体积、表面积均应纳入考虑。仅有上颌尖牙间牙弓宽度减小,不能作为上颌尖牙阻生的特异性判断指标。