模型重叠评价上颌切牙牙轴变化的可靠性研究

目的 探讨运用模型重叠的方法 评价上颌切牙牙轴变化的可靠性。方法 选取28例完成正畸治疗的患者,入选标准包括上颌对称拔除第一或者第二前磨牙,无偏斜的上颌中线等。治疗前、后拍头颅侧位片和制取寄存模型。头影测量分析头颅侧位片的中切牙牙轴变化,模型用Roland LPX-1200三维点激光扫描仪数字化,基于腭部区域重叠,使用测量软件(Rapidform 2006)分析治疗前后中切牙牙轴变化。用SPSS10.0统计软件对两种测量方法的结果行统计分析。结果 本研究样本的头影测量显示切牙牙轴平均内收14.47°,模型测量中切牙有14.70°的牙冠舌向移动。两种测量方法没有显著性差异。结论 用模型重叠的方法分析切牙的牙轴变化可以取得与头影测量一致的结果。?     

传统模型与三维数字化模型在平整牙弓间隙分析中的比较研究

目的 比较传统模型与三维数字化模型在间隙分析中的差异，并且应用数字化模型来准确计算平整牙弓所需间隙。验证传统模型分析中对平整牙弓所需间隙的方法是否正确。方法 随机选择30个正畸治疗前的石膏模型，用激光扫描的方法制作这30模型的数字化模型。在数字化模型上比较Spee曲线深度与平整牙弓所需间隙的差异，判断是否可以用Spee曲线深度来代替平整牙弓所需间隙；为了验证在正畸治疗中，Spee曲线深度的变化与由此带来的牙弓长度的变化的关系，选择另外22个正畸病例，比较在实际治疗正畸治疗前后Spee曲线深度的变化值与牙弓长度的变化值是否一致。结果在数字化模型上，Spee曲线深度的．测量值大于平整牙弓所需间隙的测量值，正畸治疗前后Spee曲线深度变化值要大于因此产生的牙弓长度变化值，且差异都具有显著性，因此临床上所认为的每平整牙弓1mm则需要1mm的牙弓间隙过多估计了平整牙弓所需间隙，二者的关系不是1：1。而是2：1。甚至3：1的关系。结论临床上传统的模型测量所认为的每平整牙弓1mm则需要1mm的牙弓间隙是错误的：在正畸临床上，三维的数字化模型测量分析方法比传统的模型测量分析方法有更多的优越性。     

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。     

萌出诱导矫治器治疗儿童上颌中切牙间隙的临床初探及三维数字化技术分析

目的 探讨萌出诱导矫治器治疗儿童上颌中切牙间隙的效果,并借助三维数字化技术进行分析.方法 对13例存在上颌中切牙间隙的病例应用萌出诱导矫治器进行矫治,应用SmartOptics Activity 880牙颌模型扫描仪,获取患儿治疗前后三维牙颌数字模型,应用三维逆向工程软件测量上、下中切牙在三维方向上的移动变化.对矫治前后覆(牙合)覆盖的测量值,应用配对t检验进行比较,以双侧P＜0.05为差异有统计学意义.结果 11例病例上中切牙间隙完全关闭,左右上中切牙平均近中位移量分别为1.17±0.20 mm和1.23±0.22 mm,平均覆(牙合)由治疗前的4.97±1.49 mm减小为治疗后的2.61±0.79 mm(t=8.083,P＜0.05),平均覆盖由治疗前的4.95±1.86 mm减小为治疗后的2.66±0.58 mm(t=5.723,P＜0.05),差异均有显著性.结论 萌出诱导矫治器可以治疗儿童上颌中切牙间隙,在关闭牙间隙的同时有改善覆(牙合)覆盖的作用.     

非接触式牙颌模型三维激光测量分析系统的研制

目的　研制开发非接触式牙颌模型激光扫描三维数字化系统。方法　用两个步进电机构成牙颌模型旋转与平移的合成运动 ,由一个半导体激光器和两个线阵列 (chargecoupleddevice ,CCD)摄像机获得模型表面各点的三维座标。采用VisualC 编程 ,在Windows环境下运行 ,完成扫描控制、三维图形重建及测量。结果　该系统测量范围为 70mm× 70mm× 70mm ,测量精度为 0 .0 1mm ,平均测量误差 <0 .1mm ,单颌模型扫描时间 <2 5分钟。用本系统与手工方法对 15副正常颌模型进行测量比较 ,二者间差异无显著性 (P >0 .0 5 )。结论　该系统具有精确、简单、高效、测量内容丰富、完整、直观等优点。还开发出一些以往靠手工方法无法实现的新功能。     

颅面部数字化三维影像重叠的稳定结构研究进展

随着锥形束CT技术的发展，正畸学领域的头影测量由二维层面走向三维。三维头影测量能弥补二维X线片影像资料存在的空间失真缺陷，特别是左右结构不对称的情况下，可更直观地展现患者颅面部特征。三维影像重叠是借助软件将正畸治疗前后三维数字化影像进行叠加，以比较术前术后特征部位的变化，其重叠标记物一般采取稳定的软硬组织结构。目前，对于颅面部稳定结构的研究不在少数，但并未得出统一的测量方法标准。文章就近年来对于颅面部三维影像重叠稳定结构的研究进展和应用做一综述，提出目前亟待解决的问题，对三维头影测量的发展进行分析。     

三维数字化牙颌模型的数据采集方法和测量可靠性

石膏（或人造石）模型可以很好的反映牙列的三维形态，为正畸医师的诊断设计提供重要信息，同时可以记录患者的治疗进程，是正畸医师之间相互交流的重要资料。然而，传统的石膏模型也存在以下缺点：占用大量储存空间、易损坏、不利于远距离交流。三维数字化牙颌模型可以克服以上缺点，随着三维测量技术的发展得到了广泛的应用。三维数字化模型的建立包括以下几个步骤：数据采集、数据预处理、曲面重构。其中数据采集是关键部分，数据的质量、精度都直接影响着后续的数据处理以及曲面重构。     

三维激光扫描技术建立附着体义齿的三维数字化模型

目的 :建立附着体义齿的三维数字化模型。方法 :附着体义齿利用三维激光扫描技术获得三维点云数据 ,经过处理软件形成三维数字化模型。结果 :成功建立了牙颌模型的三维数字化立体模型 ,结构准确 ,清晰。结论 :利用三维激光扫描技术建立的三维数字化立体模型是可靠的 ,经过数据压缩后 ,可以用来进行三维有限元模型的建立     

牙颌模型三维CT扫描测量分析系统的建立和研究

目的　建立计算机辅助牙颌模型三维CT扫描测量分析系统,并研究其可行性。方法　采用高分辨率螺 旋CT扫描石膏牙颌模型获得其断层图像,利用Visual C 6.0编制在Windows环境下运行的分析软件,完成三维图形 重建及测量,并采用该系统与手工方法对20副恒牙期模型进行测量,比较其结果。结果　牙颌模型三维CT系统 经检测精度合乎临床要求;且系统与手工方法测量20副恒牙期模型结果比较显示,两者间差异无显著性 (P>0·05)。结论　牙颌模型三维CT扫描测量分析系统是一套具有临床实用价值及推广意义的计算机辅助诊疗 系统。     

上颌腭骨三维有限元模型的建立

目的建立腭骨三维有限元模型,为进一步研究腭部种植支抗进行上颌扩大的可行性及其与牙支抗的对比研究建立数学模型基础。方法采用螺旋CT断层扫描成年人上颌骨,计算机图像处理和转录技术,自编程序和ANSYS软件相结合,将CT扫描图像转换为可用于有限元建模的数值图像。结果建立了上颌腭骨、部分颧弓根部的三维有限元模型。结论借助螺旋CT扫描技术和ANSYS有限元分析软件,建立上颌腭骨的有限元模型是切实可行的。该模型为上颌腭部种植支抗的生物力学研究提供了一个平台。     

Accuracy and reliability of palatal superimposition of three-dimensional digital models

Objective:To evaluate the accuracy of the superimposition of three-dimensional (3D) digital models using the palatal surface as a reference for measuring tooth movements.Materials and Methods:Maxillary plaster models were selected from 20 patients. The right and left canines, premolars, and molars were individually cut underneath the gingival margins and set up in wax (plaster model 1  =  PM1). The PM1s were scanned to create 3D digital models (digital model 1  =  DM1). Teeth on the PM1s were randomly moved (plaster model 2  =  PM2) and subsequently scanned to produce another set of 3D digital models (digital model 2  =  DM2). DM1s and DM2s were superimposed using the palatal area as reference via surface-to-surface matching software, and the changes in tooth movement were calculated. In the plaster models, the tooth movements were directly measured using the Reference Measurement Instrument. A paired t-test and a correlation analysis were performed to determine whether the two measurement methods differed significantly.Results:The means of the anteroposterior (x-axis), transverse (y-axis), and vertical (z-axis) tooth movements of the plaster models and the digital models did not differ significantly, and very high correlations were found between the plaster models and the digital models.Conclusion:From a technical point of view, the superimposition of 3D digital models using the palatal surface provides accurate and reliable measurements, but it remains to be investigated how stable the palatal surface is longitudinally after growth and/or orthopedic treatment take place.     

激光扫描法建立三维数字化牙颌模型的准确性和可靠性评价

目的 研究应用激光扫描法建立三维数字化牙颌模型的准确性和可靠性评价。方法 选择正畸治疗患者的石膏模型24 副,采用激光扫描法对石膏模型进行扫描,建立三维数字化牙颌模型,并对其牙冠宽度、牙冠高度、牙弓宽度和牙弓长度进行测量,与手工测得的结果进行比较分析。结果 石膏模型和数字化模型所有测量项目的一致性相关系数中,除双侧上颌第一前磨牙颊尖顶之间的距离(CCC=0.6307)和上颌中切牙近中接触点到右侧第一磨牙远中接触点的距离2 项测量指标结果(CCC=0.6571)良好外,其余指标的一致性都比较接近(CCC>0.7)。所有测量项目的均数差在0.017~0.862mm 之间,平均为0.104mm,D%﹤5%,部分指标存在统计学差异,但不具有临床意义。结论 基于激光扫描技术重建的三维数字化牙颌模型中,牙冠宽度和牙冠高度的准确性高,牙弓长度其次,牙弓宽度的准确性较低。     

Validation of Align Technology's Treat III digital model superimposition tool and its case application

Authors – Miller RJ, Kuo E, Choi W Objective – An assessment of the efficacy and accuracy of three‐dimensional computer‐based predictive orthodontic systems requires that new methods of treatment analysis be developed and validated. Design – Invisalign^® is a digitally fabricated, removable orthodontic appliance that has been commercially available since 1999. It is made up of two main components: 1) computerized graphical images of a patient's teeth moving through a series of stages from initial to final position; 2) pressure formed clear plastic appliances made from stereolithography models of the images in the first component. Setting and sample population – The manufacturer of Invisalign (Align Technology, Inc.) has created a software tool that can be used to superimpose digital models to evaluate treatment outcomes in three dimensions. Using this software, research was conducted to determine if a single operator could repeatedly superimpose two identical digital models using 12 selected points from the palatal rugae over 10 trials. The tool was then applied to one subject's orthodontic treatment. Experiment variables – The output from this tool includes rotations, translations and morphological changes. For this study, translations and rotations were chosen. Results – The results showed that the digital superimposition was reproducible, and that after multiple trials, the superimposition error decreased. The average error in x, y, z, Rx, Ry and Rz after 10 trials was determined to approach approximately 0.2 mm in translation and less than 1° in rotation, with a standard deviation of 0.15 mm and 0.7 mm, respectively. The treatment outcome from a single Invisalign‐treated bicuspid extraction case was also evaluated tooth‐by‐tooth in x, y, z, Rx, Ry and Rz dimensions. Conclusion – Using the palate, as a stable reference seemed to work well and the evaluation of the single case showed that many, but not all, of the planned movements occurred.     

The reliability of Little's Irregularity Index for the upper dental arch using three dimensional (3D) digital models

Aim

To investigate the inter-examiner variability of contact point displacement measurements (used to calculate the overall Little's Irregularity Index (LII) score) from digital models of the maxillary arch by four independent examiners.

Methods

Maxillary orthodontic pre-treatment study models of ten patients were scanned using the Lava(tm) Chairside Oral Scanner (LCOS) and 3D digital models were created using Creo^® computer aided design (CAD) software. Four independent examiners measured the contact point displacements of the anterior maxillary teeth using the software. Measurements were recorded randomly on three separate occasions by the examiners and the measurements (n = 600) obtained were analysed using correlation analyses and analyses of variance (ANOVA).

Results

LII contact point displacement measurements for the maxillary arch were reproducible for inter-examiner assessment when using the digital method and were highly correlated between examiner pairs for contact point displacement measurements >2 mm. The digital measurement technique showed poor correlation for smaller contact point displacement measurements (<2 mm) for repeated measurements. The coefficient of variation (CoV) of the digital contact point displacement measurements highlighted 348 of the 600 measurements differed by more than 20% of the mean compared with 516 of 600 for the same measurements performed using the conventional LII measurement technique.

Conclusions

Although the inter-examiner variability of LII contact point displacement measurements on the maxillary arch was reduced using the digital compared with the conventional LII measurement methodology, neither method was considered appropriate for orthodontic research purposes particularly when measuring small contact point displacements.     

三维数字化模型测量牙齿和牙弓的精确性研究

目的 通过与手工测量法比较,评估三维数字化法模型测量牙齿和牙弓的可靠性和精确性。方法 选择喀什地区维吾尔族成年人石膏模型150副,采用结构光扫描仪对石膏模型扫描获得三维图像后,运用Geomagic Studio 13.0分析软件进行分析和测量,分别测量牙冠高度、宽度、牙弓长度和宽度,与手工测量方法进行比较和分析。结果 虽然三维数字化法与手工法测得的牙冠宽度、高度和牙弓长度的部分数值具有统计学差异,但不具有临床意义,组内相关系数均>0.75。结论 结构光数字化模型的准确性好,在临床的诊断和治疗过程中可替代石膏模型。     

三维整合牙颌模型的精度研究

目的:将基于锥形束计算机断层扫描(CBCT)的牙颌模型和激光扫描的牙冠模型整合建立三维整合牙颌模型,研究三维整合牙颌模型的整合精度.方法:选择10例需要接受CBCT检查的错(牙合)患者,对每例患者头颅进行CBCT扫描,采取牙列硅橡胶印模进行激光扫描,分别重建获得三维CBCT图像和激光扫描三维图像,将三维CBCT图像和激...     

Evaluation of the use of digital study models in postgraduate orthodontic programs in the United States and Canada

Objective:To investigate the extent, experience, and trends associated with digital model use, as well as the advantages of using a particular study model type (digital or plaster) in postgraduate orthodontic programs in the United States and Canada.Materials and Methods:An electronic survey consisting of 14 questions was sent to 72 program directors or chairpersons of accredited orthodontic postgraduate programs in the United States and Canada.Results:Fifty-one responded for a 71% response rate. Sixty-five percent of the schools use plaster study models compared with 35% that use digital models. The most common advantages of plaster models were a three-dimensional feel and the ability for them to be mounted on an articulator. The most common advantages of digital models were the ease of storage and retrieval, and the residents'' exposure to new technology. About one third of the plaster model users reported that they wanted to switch to digital models in the future, with 12% planning to do so within 1 year.Conclusions:Based on our study, 35% of accredited orthodontic postgraduate programs in the United States and Canada are using digital study models in most cases treated in their programs, and the trend is for increased digital model use in the future.     

Accuracy of metal 3D printed frameworks for removable partial dentures evaluated by digital superimposition

ObjectivesTo evaluate the accuracy of metal 3D printed frameworks (MEP group) for removable partial dentures (RPDs) by digital superimposition, in comparison to that of frameworks produced by the conventional (CON group) and resin printing/casting (RPC group) workflows.MethodsA partially edentulous maxillary dentiform was prepared with rest seats and guiding planes on the right canine, left first premolar, and left second molar. Thirty master casts were prepared via repeated impressions of the dentiform. Frameworks were fabricated by three different workflows (n = 10 for each group). The internal discrepancies of the frameworks were assessed at 12 points by digital scanning with an optical triangulation principle-based tabletop scanner and superimposition using a reference best-fit alignment method. First, the master cast was scanned alone. Subsequently, a thin silicone material was applied to the framework and fitted onto the master cast, after which the framework was removed. Finally, the master cast with the silicone material attached was rescanned. The data from the two scans were matched, with the reference being the area not occupied by the silicone.ResultsFor the CON, MEP, and RPC groups, respectively, the mean overall internal discrepancies (279.72 µm, 241.02 µm, and 331.70 µm), and the mean internal discrepancies on palate areas (292.92 µm, 250.72 µm, and 355.84 µm) and rest seat areas (240.12 µm, 211.91 µm, and 259.26 µm) did not significantly differ among the three fabrication methods (p = 0.558, 0.542, and 0.774).SignificanceThe reference best-fit alignment of scan datasets is a useful approach to evaluate the internal discrepancy of frameworks. Metal 3D printing produces RPD frameworks that are comparable to conventional frameworks and meet clinical standards.