利用工业CT扫描图像重建牙列缺损的几何模型

目的:介绍一种获取牙列缺损石膏模型三维数据的方法,为实现可摘局部义齿CAD/CAM奠定基础。方法:利用低能量X射线工业计算机断层扫描机(industrialcomputedtomography,ICT)扫描牙列缺损石膏模型,获得该模型的ICT图像,经过图形图像处理,获取表面轮廓三维数据;矢量化后,将数据输入通用逆向工程软件系统,重建牙列缺损的三维CAD模型。在此基础上,在CAD/CAM软件系统中构建可摘局部义齿支架的三维数字模型。数据传输格式为STL。结果:获得的点云数据密集均匀,未见扫描盲区;三维重建的牙列缺损CAD模型结构清晰,完成了可摘局部义齿支架三维模型的构建。结论:与医用CT相比,ICT扫描方法空间分辨率高,精确度高,可以作为一种获取牙列缺损石膏模型三维数据的可靠方法。     

光栅投影技术在获取牙列缺损三维数据中的应用

目的 介绍一种采集牙列缺损石膏模型三维数据的方法,为重建牙列缺损三维数字模型及研究可摘局部义齿支架的计算机辅助设计奠定基础。方法 利用计算机控制投影系统在0.4 s的时间内连续将间隔∏/2正弦周期4幅光栅,投射在牙列缺损石膏模型表面,数码相机采集由于受到模型表面高度的调制而变形的条纹图像,通过相移法解调得到包含高度信息的相位变化, 去包裹后的位相值通过三角测量法实现相位-高度的转换,计算机自动完成多视数据拼合,从而得到整个石膏模型外形轮廓的三维数据,重建牙列缺损的三维数字模型。结果 获得了密集完整的牙列缺损点云模型,基本上未见扫描盲区。重建的牙列缺损三维模型牙颌解剖结构清晰。结论 采用光栅投影和相移法获取牙列缺损的三维数据,具有精度高速度快的特点,可以满足后续的可摘局部义齿支架三维设计的需要。     

应用激光近形制造方法制作口腔修复体的基础研究--牙颌石膏模型的层析三维测量

目的:实现牙颌模型的精确三维测量信息贮存,为口腔修复体的激光近形制作和CAD/CAM奠定基础。方法:采用层析三维数字化仪,逐层铣出并扫描测量被测牙颌石膏模型的断面,经图象处理精确求出断面二维边缘轮廓数据,由断面边缘轮廓数据叠加重建牙颌模型。结果:获得了全牙列石膏模型断面边缘轮廓图和三维显示模型。结论:层析三维测量可对形状复杂的全牙列石膏模型进行精确、自动测量,避免了光学测量难以克服的测量盲区问题     

应用激光近形制造方法制作修复体的基础研究—牙颌石膏模型的层？…

目的：实现牙颌模型的精确三维测量信息贮存，为口腔修复体的激光近形制作和ＣＡＤ／ＣＡＭ奠定基础。方法：采用层析三维数字化仪，逐层铣出并扫描测被测牙颌石膏模型的断面，经力象处理精确求出断面二维边缘轮廓数据，由断面边缘轮廓数据叠加重建牙颌模型。结果：获得了全牙列石膏模型断面边缘轮廓图和三维显示模型。结论：层析三测量可对形状复杂的全牙列石膏模型进行精确、自动测量，避免了光学测量难以克服的测量盲区问题。     

不同扫描方法重建上颌牙列数字化模型的三维对比分析

目的以常规石膏模型三维扫描重建的牙列数字化模型为参考,对比分析口内直接扫描法、硅橡胶印模扫描法重建的上颌牙列数字化模型与参考模型的一致性。方法随机筛选门诊正畸就诊患者20人,年龄18-32岁,分别采用口内直接扫描法,硅橡胶印模扫描法,石膏模型扫描法重建患者上颌牙列数字化模型。以石膏模型扫描重建的数字化牙列模型为参考模型,通过三维图形最佳拟合配准技术,对比分析口内扫描法、硅橡胶印模扫描法重建的同一患者牙列数字化模型与参考模型的一致性。结果口内扫描、印模扫描与石膏模型扫描重建的数字化牙列模型的平均差异分别为92.80±5.033μm和104.75±5.981μm。结论印模扫描、口内扫描与石膏模型扫描重建的牙列数字化模型存在显著差异,如何获得更准确的数字化模型还有待进一步研究。     

应用反求工程方法重建残冠和(或)残根的三维数字模型

目的 探讨用反求工程(RE)方法实现残冠和(或)残根数字模型三维重建的方法,为个体化桩核的CAD设计与制作奠定基础.方法 (1)选取牙体硬组织完整的离体牙10颗,按桩核预备标准预备后分别用螺旋CT机和Mi-CT机进行扫描,所获得数据以DICOM格式文件进行存储;(2)应用Mimics软件将螺旋CT机和Mi-CT机扫描获得的数据分别进行处理,获得牙齿标本的数字模型,Geomagic 9.0软件进行三维测量,同时生成STL格式文件:(3)用游标卡尺对牙齿标本进行测量,并与软件测量所获得的数据进行比较,采用配对比较t检验进行统计学分析.结果 (1)用反求工程方法对离体牙标本实现了三维重建,获得其数字模型.Mi-CT数据源三维数字模型较螺旋CT数据源三维数字模型而言,模型边缘轮廓更为锐利、清晰;(2)应用螺旋CT机和Mi-CT机扫描获得的数字模型,经软件测量,与牙齿标本测量结果相比均无统计学意义(P>0.05).结论 用反求工程方法能准确、快速地实现残冠和(或)残根模型的三维重建.     

基于工业用CT断层影像的牙列缺损模型三维构建

目的 介绍一种获取牙颌模型计算机辅助设计（computer assisted design，CAD）可利用数据的方法。方法 利用低能量工业计算机断层扫描（industrial compued tomography，ICT）机扫描标准牙列缺损石膏模型。通过三维重建获得该模型的CT图像，经过图形图像处理后得到边缘轮廓数据，将数据输入逆向工程软件系统，建立牙列缺损石膏模型的CAD模型。结果 实现了牙列缺损石膏模型的几何模型重建。结论 该扫描方法速度快，空间分辨率高，精确度高，可以得到密集、完整的点云数据，几何模型可编辑性强，有利于后期可摘局部义齿的计算机辅助设计、有限元分析和快速成型加工。     

Micro CT重建牙测量模型替代传统石膏测量模型的可行性研究

目的：探讨用Micro CT重建全牙列三维数字化模型替代传统石膏模型进行牙冠外形测量的可行性。方法：用游标卡尺测量上下颌7-7离体牙牙冠的冠宽、冠厚和冠高,作为基准数据;然后用离体牙翻制出上、下颌全牙列石膏模型,分别用游标卡尺和Micro CT自带软件测量牙冠的宽、厚、高;应用统计分析方法,评价各测量方法的可靠性和准确性。结果：利用Micro CT扫描石膏模型获得了精确的三维数字化模型;每项实验中各组数据间呈高度相关性且无明显差异（P〈0.001）;以离体牙测量结果为标准,Micro CT测量的误差范围为-0.338～0.338mm,石膏模型手工测量的误差范围为-0.408～0.408mm。结论：Micro CT可生成高精度的全牙列数字化模型,便于测量和储存,其牙冠外形的测量精度高于石膏模型。     

数字化三维牙颌模型测量系统的可靠性对比研究

目的 检验由我院和清华大学共同研制开发的建立于层析扫描技术基础上的牙颌模型数字化三维重建系统之测量软件的可靠性。方法 选择不同牙列期的患者20例，常规取印模并灌制成两副牙颌模型，组成为两个配对的样本；其中样本1保留为石膏模型，样本2由三维模型重建系统生成数字化的模型影像；由同一操作者间隔3周分别对石膏模型和数字模型的牙齿宽度、牙弓宽度和牙弓长度等测量项目进行两次测量。结果 数字化模型两次测量结果的差值经秩和检验表明无统计学差异；经两组样本各测量项目两次测量结果之差数的￡检验表明，牙弓宽度两次测量结果的差异在石膏模型和数字模型间无显著性；而牙弓长度和牙齿宽度两次测量结果的差异具有显著性。结论 三维重建系统可生成真实的数字化牙颌模型影象，系统测量软件能提供可靠的测量数据且其精确性明显优于石膏模型。     

锥形束CT在三维数字化牙模建立中的初步应用

目的:研究应用锥形束CT(CBCT)采集数字化牙模的可靠性.方法:选择口腔正畸科门诊下颌前牙拥挤需要进行正畸治疗的成人患者共10例,常规取下颌印模并灌制成牙(牙合)模型.应用NewTom CBCT,选择6inch视野扫描石膏模型,重建三维数字牙模.由同一操作者间隔1周分别对石膏模型和数字模型的右下颌第一前磨牙宽度、牙弓宽度、牙弓长度和下前牙宽度等测量项目进行2次测量.应用配对t检验分析各测量项目在石膏模型和数字化模型测量间的差异,计算同一测量项目间隔1周并比较2种模型前后2次测量的绝对差别程度.采用SPSS13.0软件包对数据进行统计学处理.结果:2种模型上测量右下颌第一前磨牙宽度、牙弓宽度、牙弓长度、右下颌第一切牙宽度均无统计学差异.但在石膏模型上,测量所有下前牙宽度之和大于数字化模型上的测量值,有统计学差异(P<0.05).同一测量者在石膏模型上前后2次测量差值绝对值和数字化模型差值绝对值无显著差异(P>0.05).结论:CBCT生成的数字化牙(牙合)模型,与石膏模型线距测量结果的差别无显著性,应用CBCT重建的三维数字化牙(牙合)模型可作为研究模型来存储、测量.     

Three-dimensional assessment of dental casts' occlusal surfaces using two impression materials

The aim of this study was to assess by means of a three-dimensional computed tomography scanning system the occlusal surface characteristics of dental casts made using two different impression materials. Alginate and polyvinyl siloxane impressions were taken of 20 dental students resulting in 40 dental casts. The casts were paired for each student separately so that each pair consisted of an alginate poured cast and a polyvinyl siloxane poured out cast. The casts were scanned using FlashCT scanner and for each cast, a three-dimensional digital image was obtained. The digitized casts were processed using the three-dimensional imaging software Geomagic Studio 9. A total of 464 paired teeth were digitally separated and superimposed. For each tooth, two measurements were obtained corresponding to the two different impression materials used. The two sets of volumes for all digitally separated teeth were compared and analysed using the Wilcoxon signed test. Larger volume measurements were obtained for teeth separated from alginate poured out casts than from their corresponding ones from polyvinyl siloxane casts (P = 0.005). When the teeth were divided into the groups of incisors, canines and premolars/molars, only the last one exhibited significant difference (P = 0.00). The mean difference between the volumes measured for all 464 teeth separated was 0.041 mm(3) (+/-0.33). The occlusal surfaces of teeth appear differently in dental casts depending on the impression materials used. Impressions of dental casts should be utilized with caution in relation to their research application and in reference with dental wear studies.     

Evaluation of dental arch reproduction using three-dimensional optical digitization

STATEMENT OF PROBLEM: Numerous investigations have been done to determine the most accurate method to reproduce a dental arch. Investigations have used different definitive cast configurations, materials, and measuring techniques to evaluate dimensional change, leaving clinicians undecided as to the most accurate method to reproduce a dental arch. PURPOSE OF STUDY: The purpose of this investigation was to evaluate the effect of impression tray selection on accuracy of reproductions of a dental arch using a 3-dimensional optical digitizer. MATERIALS AND METHODS: Impressions were made of a stone cast of a dental arch using vinyl polysiloxane impression material in custom and stock impression trays (n=12). Custom trays, designed with full palatal coverage, were fabricated on a separate standard stone cast using 2 layers of pink baseplate wax as the spacer and tissue stops on 1 anterior tooth and both first molar teeth. Impressions were poured with type IV gypsum and allowed to set with the tray inverted (n=5) or not inverted (n=5). The standard cast and resulting casts were digitized using an optical digitizer. Custom software was used to align and process the 3-dimensional images created by the digitizer. Each image was superimposed onto the standard cast image, curves were created of the percent of points less than a defined distance between the 2 superimposed images, and the area under the curve was calculated. A weighted average area was calculated for each cast, and these values were analyzed using a 2-way ANOVA (alpha=.05). RESULTS: The main effect of tray type, laboratory setting technique, and the interaction between these 2 characteristics was analyzed. None of these effects was significant. CONCLUSION: The differences in accuracy of reproductions of a dental arch, regardless of the impression and laboratory techniques, were not significant when evaluated using a 3-dimensional optical digitizer.     

摄影测量与传统印模技术制取牙列缺失种植修复印模精度的比较研究

目的:通过体外实验对比摄影测量与传统印模技术制取牙列缺失种植修复印模的精度。方法:选择1例2019年9月就诊于首都医科大学口腔医学院种植中心的74岁男性上颌牙列缺失患者的上颌石膏模型,其上含螺丝固位基台替代体8个。通过开窗夹板式印模复制该石膏模型,将复制模型作为参考模型。由同1名主治医师用两种方法制取参考模型种植体基台...     

Laser digitization of casts to determine the effect of tray selection and cast formation technique on accuracy

STATEMENT OF PROBLEM; Several studies have attempted to determine the ideal combination of dental materials and laboratory techniques to produce the most accurate dental cast. Most have made use of 2-dimensional manual measuring devices, which neglect to account for the dimensional changes that exist along a 3-dimensional surface. PURPOSE: The purpose of this study was to determine the effect of impression tray selection and cast formation techniques on the dimensional change of a dental cast with the use of new, 3-dimensional optical digitizing technology. MATERIAL AND METHODS: Multiple impressions of a machined steel die that resembled a dental arch were made with custom and stock impression trays and vinyl polysiloxane impression material. The impressions were poured in type V artificial dental stone and allowed to set with the tray inverted or noninverted. The steel master die and stone casts were digitized with the Steinbichler Comet 100 Optical Digitizer, which was developed at the Minnesota Dental Research Center for Biomaterials and Biomechanics. Three-dimensional images of the stone casts were aligned to the 3-dimensional image of the master die and analyzed with AnSur-NT software. Multiple measurements of the master die and stone casts were analyzed to determine the accuracy of the 3-dimensional technology and of the impression and cast fabrication techniques. Planar distances between the center of each crown preparation were measured, as were crown heights. Data were analyzed with analysis of variance (P<.05), and root mean square error values were determined. RESULTS: Casts were compared with a total of 45 significance tests, of which only 4 yielded P<.05. There was no pattern to these results, which suggests that they were false-positive findings. CONCLUSION: Results obtained with the use of new optical digitizing technology indicated that neither impression tray type nor cast formation technique affected the accuracy of final casts.     

A Digital Technique to Replicate Edentulous Arches with Functional Borders and Accurate Maxillomandibular Relationship for Digital Complete Denture

Correct functional border impression and jaw registration is a challenge when edentulous arches are directly digitized with an intraoral scanner. This article describes a digital workflow to replicate complete edentulous arches with full functional contour, and position them in the centric relation using an intraoral scanner, existing denture, and three‐dimensional image reversal technique. Based on the reconstructed images, the base and dental parts of the new denture can be designed efficiently and predictably.     

2种不同印模方法致上颌游离缺失端黏膜组织形变量差异分析

目的: 比较光学印模与功能性印模技术制取的牙列缺损上颌模型致游离端黏膜组织形变量的差异。方法: 选取Kennedy第一类和第二类上颌牙列缺损患者各10例,分别使用光学印模和功能性印模技术为同一患者制取2个上颌模型。将功能性印模所翻制的石膏模型使用口外台式扫描仪获得的三维图像作为参照模型,在Geomagic Qualify 12 软件中,将同一患者的光学印模与功能性印模进行比对,得到偏差色谱图。采用 SPSS 20.0 软件包对数据进行统计学分析。结果: Kennedy第一类和Kennedy第二类缺牙组间的平均偏倚均方根差（Root Mean Square,RMS）无统计学差异（P>0.05）;所有病例均呈现随着与末端基牙距离的增加,平均RMS随之上升的趋势。结论: 光学印模与功能性印模对上颌游离端缺牙区黏膜组织形变量的差异与缺牙类型无明显相关性,与游离缺牙区的长度呈现正相关趋势,需扩大样本量进一步验证。     

Factors influencing optical 3D scanning of vinyl polysiloxane impression materials

PURPOSE: Future growth in dental practice lies in digital imaging enhancing many chairside procedures and functions. This revolution requires the fast, accurate, and 3D digitizing of clinical records. One such clinical record is the chairside impression. This study investigated how surface angle and surface roughness affect the digitizing of vinyl polysiloxane impression materials. MATERIALS AND METHODS: Seventeen vinyl polysiloxane impression materials were digitized with a white light optical digitizing system. Each sample was digitized at 3 different angles: 0 degrees, 22.5 degrees, and 45 degrees, and 2 digitizer camera f-stops. The digitized images were rendered on a computer monitor using custom software developed under NIH/NIDCR grant DE12225. All the 3D images were rotated to the 0 degrees position, cropped using Corel Photo-Paint 8 (Corel Corp, Ottawa, Ontario, Canada), then saved in the TIFF file format. The impression material area that was successfully digitized was calculated as a percentage of the total sample area, using Optimas 5.22 image processing software (Media Cybernetics, LP, Silver Spring, MD). The dependent variable was a Performance Value calculated for each material by averaging the percentage of area that digitized over the 3 angles. New samples with smooth and rough surfaces were made using the 7 impression materials with the largest Performance Values. These samples were tested as before, but with the additional angle of 60 degrees. Silky-Rock die stone (Whip Mix Corp, Louisville, KY) was used as a control. RESULTS: The Performance Values for the 17 impression materials ranged from 0% to 100%. The Performance Values for the 7 best materials were equivalent to the control at f/11 out to a surface angle of 45 degrees; however, only Examix impression material (GC America Inc, Alsip, IL) was equivalent to the control at f/11/\16. At the 60 degrees surface angle with f/11/\16, the Performance Values were 0% for all the impression materials, whereas that for the control was 90%. The difference in the Performance Values for the smooth and rough surface textures was 7%, which was not significant. CONCLUSIONS: The digitizing performance of vinyl polysiloxane impression materials is highly material and surface angle-dependent and is significantly lower than the die stone control when angles to 60 degrees are included. It is affected to a lesser extent by surface texture.     

EVALUATING NOISE IN DIGITIZED RADIOGRAPHIC IMAGES BY MEANS OF HISTOGRAM

To evaluate the performance of three digital devices regarding the noise added to digital radiographic images containing different optical densities.

Methods:

A radiographic image was digitized repeatedly ten times using two scanners (HP 4c/T and HP 5370C) and a digital camera (Nikon 990). A histogram tool measured a mean pixel value and the standard deviation of the region of interest in each image. Both values were used to calculate the image noise at the different optical densities.

Results:

The noise values found were different for all devices and optical densities. There was a statistically significant difference (p<0.05) between the scanner HP 4c/T and the digital camera regarding the noise values. There was a significant correlation (p<0.05) between the noise values found for the HP 4c/T scanner and the digital camera and between both scanners (p<0.01).

Conclusions:

The noise added to the image was higher for scanner HP 4c/T and less for the digital camera. The noise was higher at the lower optical densities for the scanners. It seems that depending on the equipment and the optical density, a variable amount of noise can be incorporated to the images.     

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。     

上颌埋伏尖牙CT影像分型系统的建立和分析

目的 利用螺旋CT三维重建技术建立适合上颌埋伏尖牙的影像学分型系统。方法 选择102例上颌埋伏尖牙患者为研究对象,共121颗上颌埋伏尖牙。所有患者均接受标准的螺旋CT扫描,数据均导入MIMICS 10.01软件采用表面遮盖成像法进行三维重建。通过对121颗上颌埋伏尖牙的三维空间位置进行分析建立上颌埋伏尖牙的影像学分型系统。结果 本研究建立了一个上颌埋伏尖牙的三维CT影像学数据库。研究结果显示在X轴方向上,最常见的分型是牙尖近中伴根尖正常。在Y轴方向上,样本中所有埋伏尖牙只存在3种分型即根尖均处于高位,牙尖分别处于高、中、低位。在Z轴方向上,最常见的分型是牙尖和根尖均处于唇侧,约占总数的三分之一。结论 本研究利用螺旋CT建立了一个适合上颌埋伏尖牙的三维影像学分型系统,具有一定的临床诊断价值。