2种三维颜面部扫描仪测量精度的定量评价

目的：对三维颜面部扫描仪进行真人实际测量精度评价。方法：分别应用三维颜面部扫描仪3dMD 和 FaceScan 获取10名正常面型志愿者的三维面相数字模型，测量每个模型上的10个特征线段长度和5个特征角度，并分别与高精度线激光扫描仪（Faro）获取的参考值进行统计学分析和测量学分析，计算面貌特征测量误差与实际测量精度。结果：3dMD 和 FaceS-can 对正常面型人群的长度测量精度分别为（－0．37±0．68）mm 和（－0．29±0．53）mm（P ＝0．223），角度测量精度分别为（－0．22±2．14）°和（0．12±2．69）°（P ＝0．428）。结论：2种三维面部扫描仪获取的三维面相数据无显著差异。     

量匙精确控制超硬石膏水粉比灌注义齿修复模型临床应用观察

目的：利用量匙精确控制超硬石膏水粉比灌注义齿修复工作模型，保证模型质量，节约资源。方法：通过测量、统计临床灌模的超硬石膏粉用量进行分类，以此为设计并制作量匙，临床试用并调整。量匙组、熟练技工手工组为实验组，标准下颌组为对照组，采用SPSS13．0统计软件单样本t检验进行精度和硬度比较，以P〈0．05认为有统计学意义。结果：量匙设计为半球形，内径大小依次为29．91mm、28．29mm、26．46mm；量匙组精度和表面硬度与标准下颌模型比较无差异（P〉0．05），手工组精度和表面硬度与标准下颌模型比较有明显差异（P〈0．05）。结论：量匙可精确控制超硬石膏水粉比，保证模型精度和硬度，提高义齿修复体的质量。     

3dMD摄影测量系统在半侧颜面短小诊断中的初步应用

目的:建立一种新的三维测量方法辅助半侧颜面短小综合征的诊断。方法 :应用3dMD摄影系统对半侧颜面短小综合征患者进行摄影,用其配套的软件包重建患者三维软组织图像,测量并分析患侧头面部软组织与健侧的差异,辅助半侧颜面短小综合征的诊断及病情分析。结果:半侧颜面短小综合征患者健、患侧软组织间的差异可以表现在两侧的软组织容积差。结论:3dMD摄影系统,可以辅助评价半侧颜面短小综合征患者的颌面部软组织变异情况。     

表面多孔涂层对氧化锆与饰面瓷界面结合强度的影响

目的：以表面抛光、喷砂为对照,研究表面多孔涂层对氧化锆与饰面瓷界面剪切结合强度的影响。方法：按照Schmitz-Schulmeyer法测量氧化锆与饰面瓷的剪切结合强度。制作氧化锆基底样本60个（IO×5×5mm）,分为三组（抛光组：耐水碳化硅砂纸逐级抛光至1200#;喷砂组：1lOμmA1203颗粒在3bars的压力下喷砂10sec,距离10mm;涂层组：质量分数为55wt％的氧化锆粉浆涂塑氧化锆表面,致密烧结）,每组20个。表面烧结饰面瓷（5×3×3mm）。每组取10个样本,5℃／55℃水域中交替循环5000次。万能材料试验机测试剪切结合强度,加载速度0．5mm／min。对测试结果进行双因素方差分析（α=0．05）。SEM观察样本断裂模式。结果：涂层组剪切结合强度与抛光组和喷砂组差异均有统计学意义（P〈0．05）;喷砂组与抛光组间差异无统计学意义（P〉0．05）;各组温度循环后剪切结合强度差异均无统计学意义（P〉0．05）。SEM观察显示,涂层组样本以饰面瓷的内聚断裂为主;抛光组和喷砂组以界面断裂为主。结论：表面多孔涂层可显著提高氧化锆与饰面瓷的剪切结合强度,并能耐受短期的人工老化,而结合强度无明显下降。     

西安地区汉族青年面部形态角度相关性的初步研究

目的：观察分析西安地区汉族青年面部形态角度的相关性。方法：纳入面形正常无手术及外伤史的西安市汉族18～40岁居民60名（男女各30名）,进行头面部三维立体扫描,用3dMD 软件自带测量系统在扫描影像上定点并测量面部12个常用角度,用 SPSS 19．0将结果进行统计分析,计算面部各角度之间的相关性及相关性回归公式。结果：获得12个面部角度的均值及标准差,男性鼻额角大于女性（P ＜0．05）,其余角度无性别差异（P ＞0．05）,5个角度之间存在7组相关关系（R≥0．7）,其中4组为正相关,3组为负相关;得到7个相关性回归方程。结论：面部角度之间彼此协调相关。     

超硬石膏材料水粉比对模型精度和表面硬度的影响

目的：观察水粉比对超硬石膏制取全牙列模型精度和表面硬度的影响。方法：制取一个标准下颁牙列金属母模。用两种水粉比（22：100;25：100）调拌超硬石膏材料,制取20个模型,每组10个。用测量显微镜测量模型各标志点的距离,用布洛维硬度机测量模型表面硬度,所得数据进行统计分析。结果：①不同水粉比制备超硬石膏模型,模型各线段长度变化无明显统计学意义（P〉0．05）;②当超硬石膏的水粉比增大为25g：100g时,模型的表面硬度出现显著的变化（P〈0．01）,从数值可看出为硬度的降低。结论：①适当增加水粉比,模型仍可获得较高的精度。②随着水粉比的增加,模型表面硬度和抗磨损性降低。     

不同数字印模技术对3D 打印模型精度的影响

目的：结合3D 打印树脂模型评价2种椅旁扫描系统的扫描精度。方法：仿照上颌牙弓形态及大小制作一金属底座主模型,底座上设计4个柱形金属预备体,分别模拟上颌尖牙和第一磨牙的预备体,右侧尖牙和第一磨牙分别以 A、B 表示,左侧分别以 C、D 表示。分别利用 Cerec 蓝光照相系统和 Cerec 真彩摄像系统扫描主模型各10次,每次扫描生成一个数字化模型。用3D 打印机打印出树脂模型（n ＝10）,在三坐标测量机上分别测量主模型和树脂模型相应柱形金属预备体间的距离 AB、AC、BD 以及 A 的直径 d。采用 SPSS 13．0软件对测量结果进行统计分析。结果：蓝光组 AB、AC、BD 的距离,真彩组 AC、BD的距离分别与主模型差异有显著性（P ＜0．05）;蓝光组与真彩组各距离差异均有显著性（P ＜0．05）。2组的 d 值与主模型差异无显著性（P ＞0．05）。结论：对单个预备体的扫描,Cerec 蓝光照相系统精度高于 Cerec 真彩摄像系统;当扫描区域扩大,Cerec真彩摄像系统精度高于 Cerec 蓝光照相系统。     

计算机软件在三维面部成像与测量中的应用进展

如今三维面部成像技术在整形外科、正畸科等颜面部美学相关学科中变得越来越重要。三维面部成像的发展与计算机技术的广泛应用密切相关,三维激光扫描、锥型束CT(CBCT)、3dMD立体摄影系统、卷积神经网络等在面部测量分析中的应用均是两者紧密结合的结果,将医生与患者的沟通、治疗计划和结果评估提升到了一个新的水平。现代计算机软件技术正在日益成为临床医师的重要辅助工具。本文就各类软件技术在三维面部成像与测量中的具体应用及其特点作一综述。     

安氏Ⅱ类1分类患者后牙区颊侧皮质骨厚度分析

目的探讨不同年龄和性别的安氏Ⅱ类1分类患者后牙区颊侧皮质骨厚度的差异,为临床精准植入微种植钉提供理论依据。方法选取安氏Ⅱ类1分类患者多层螺旋CT三维重建影像资料88例,分为青少年男性组、青少年女性组、成年男性组和成年女性组4组,各组病例数为22例,测量上颌第二双尖牙和第一恒磨牙间及下颌第一、第二磨牙间,距离牙槽嵴顶3、5、7mm水平的颊侧皮质骨厚度,并对测量结果进行统计学分析。结果上颌第二双尖牙和第一恒磨牙间距离牙槽嵴顶3、5、7mm水平的颊侧皮质骨厚度分别为（1．21±0．21）mm、（1．29±0．20）mm和（1．42±0．19）nun;下颌第一、第二磨牙间距离牙槽嵴顶3、5、7mm水平的颊侧皮质骨厚度分别为（2．23±0．30）mm、（2．70±0．30）mm和（3．09±0．27）mm。青少年组与成年组之间在各水平的颊侧皮质骨厚度差异无统计学意义（P〉0．05）;男性与女性之间在各水平的颊侧皮质骨厚度差异无统计学意义（P〉0．05）。结论上颌第二双尖牙和第一恒磨牙及下颌第一、第二磨牙间皮质骨厚度在青少年与成人之间或男女之间无明显差异;以上部位距离牙槽嵴顶3、5、7mm水平的颊侧皮质骨厚度均可满足微种植钉植入要求。     

基于三维视觉测量的上颌牙弓形态分类要素分析

目的：应用三维扫描技术分析不同牙弓形态间的共同点与差异点,寻找有统计学意义的测量指标。方法：选取上颌模型100例,将样本按不同牙弓形态分为尖圆形组、方圆形组、椭圆形组。通过三维扫描将牙列模型转化为计算机三维数据,测量上中切牙唇面至上尖牙连线距离（IIC）、双侧上尖牙牙尖之间的距离（ICW）、双侧上第一磨牙近中舌尖之间的距离（AW）。结果：不同牙弓形态组两两之间IIC值、IIC／ICW值均有显著差异（P〈0．05）;尖圆形牙弓与方圆形及椭圆形牙弓之间ICW值有显著差异（P〈0．05）。结论：IIC、ICW、IIC／ICW这3项测量指标对牙弓形态可能有着重要的影响。     

Accuracy and reliability of 3D stereophotogrammetry: A comparison to direct anthropometry and 2D photogrammetry

Objective:To evaluate the accuracy of three-dimensional (3D) stereophotogrammetry by comparing it with the direct anthropometry and digital photogrammetry methods. The reliability of 3D stereophotogrammetry was also examined.Materials and Methods:Six profile and four frontal parameters were directly measured on the faces of 80 participants. The same measurements were repeated using two-dimensional (2D) photogrammetry and 3D stereophotogrammetry (3dMDflex System, 3dMD, Atlanta, Ga) to obtain images of the subjects. Another observer made the same measurements for images obtained with 3D stereophotogrammetry, and interobserver reproducibility was evaluated for 3D images. Both observers remeasured the 3D images 1 month later, and intraobserver reproducibility was evaluated. Statistical analysis was conducted using the paired samples t-test, intraclass correlation coefficient, and Bland-Altman limits of agreement.Results:The highest mean difference was 0.30 mm between direct measurement and photogrammetry, 0.21 mm between direct measurement and 3D stereophotogrammetry, and 0.5 mm between photogrammetry and 3D stereophotogrammetry. The lowest agreement value was 0.965 in the Sn-Pro parameter between the photogrammetry and 3D stereophotogrammetry methods. Agreement between the two observers varied from 0.90 (Ch-Ch) to 0.99 (Sn-Me) in linear measurements. For intraobserver agreement, the highest difference between means was 0.33 for observer 1 and 1.42 mm for observer 2.Conclusions:Measurements obtained using 3D stereophotogrammetry indicate that it may be an accurate and reliable imaging method for use in orthodontics.     

Comparison of three methods of facial measurement

The aims of this study were to assess the accuracy of measurements recorded by 3D stereophotogrammetry and to compare three methods of facial measurement: manual anthropometry, 3D stereophotogrammetry and 2D photography. Measurements were taken from 14 landmarks on each of six volunteers and compared. In addition, the variability of the methods was assessed. Three-dimensional measurements were shown to compare well with manual measurements on volunteers as well as test objects for which the mean difference was 0.23 mm (shortest distance) and 0.13 mm (surface). All the three methods of measurement were found to have good levels of repeatability. Two-dimensional measurements were more variable than manual measurements (P=0.021). Three-dimensional stereophotogrammetric measurements were shown to compare well with manual measurements although the values obtained were mostly slightly larger. Stereophotogrammetry allows images to be taken in a Medical Photography Department, facilitating the accurate measurement of facial morphology from digitized data, including changes associated with treatment or growth. There are clear potential benefits of using 3D measurements in the assessment of facial deformity.     

A comparison between stereophotogrammetry and smartphone structured light technology for three-dimensional face scanning

ObjectivesTo compare three-dimensional facial scans obtained by stereophotogrammetry with two different applications for smartphone supporting the TrueDepth system, a structured light technology.Materials and MethodsFacial scans of 40 different subjects were acquired with three different systems. The 3dMDtrio Stereophotogrammetry System (3dMD, Atlanta, Ga) was compared with a smartphone (iPhone Xs; Apple, Cupertino, Calif) equipped with the Bellus3D Face Application (version 1.6.11; Bellus3D Inc, Campbell, Calif) or Capture (version 1.2.5; Standard Cyborg Inc, San Francisco, Calif). Times of image acquisition and elaboration were recorded. The surface-to-surface deviation and the distance between 18 landmarks from 3dMD reference images to those acquired with Bellus3D or Capture were measured.ResultsCapturing and processing times with the smartphone applications were considerably longer than with the 3dMD system. The surface-to-surface deviation analysis between the Bellus3D and 3dMD showed an overlap percentage of 80.01% ± 5.92% and 56.62% ± 7.65% within the ranges of 1 mm and 0.5 mm discrepancy, respectively. Images from Capture showed an overlap percentage of 81.40% ± 9.59% and 56.45% ± 11.62% within the ranges of 1 mm and 0.5 mm, respectively.ConclusionsThe face image acquisition with the 3dMD device is fast and accurate, but bulky and expensive. The new smartphone applications combined with the TrueDepth sensors show promising results. They need more accuracy from the operator and more compliance from the patient because of the increased acquisition time. Their greatest advantages are related to cost and portability.     

Reliability of a 3D surface laser scanner for orthodontic applications.

A device for recreating three-dimensional (3D) objects on a computer is the surface laser scanner. By triangulating distances between the reflecting laser beam and the scanned surface, the surface laser scanner can detect not only an object's length and width but also its depth. The scanner's ease of use has opened various possibilities in laboratory research and clinical investigation. We assessed the reliability of generating 3D object reconstructions using the Minolta Vivid700 3D surface laser scanner (Minolta USA, Ramsey, NJ). Accuracy and reproducibility were tested on a geometrical calibrated cylinder, a dental study model, and a plaster facial model. Tests were conducted at varying distances between the object and the scanner. It was found that (1) in the calibrated cylinder tests, spatial distance measurement was accurate to 0.5 mm (+/- 0.1 mm) in the vertical dimension and 0.3 mm (+/- 0.3 mm) in the horizontal dimension; (2) in the study model test, molar width was accurate to 0.2 mm (+/- 0.1 mm, P >.05), and palatal vault depth could be measured to 0.7 mm (+/- 0.2 mm, P > 0.05); and (3) for the facial model, an accuracy of 1.9 +/- 0.8 mm was obtained. The findings suggest that the surface laser scanner has great research potential because of its accuracy and ease of use. Treatment changes, growth, surgical simulations, and many other orthodontic applications can be approached 3-dimensionally with this device.     

Three-dimensional accuracy of different correction methods for cast implant bars

PURPOSE

The aim of the present study was to evaluate the accuracy of three techniques for correction of cast implant bars.

MATERIALS AND METHODS

Thirty cast implant bars were fabricated on a metal master model. All cast implant bars were sectioned at 5 mm from the left gold cylinder using a disk of 0.3 mm thickness, and then each group of ten specimens was corrected by gas-air torch soldering, laser welding, and additional casting technique. Three dimensional evaluation including horizontal, vertical, and twisting measurements was based on measurement and comparison of (1) gap distances of the right abutment replica-gold cylinder interface at buccal, distal, lingual side, (2) changes of bar length, and (3) axis angle changes of the right gold cylinders at the step of the post-correction measurements on the three groups with a contact and non-contact coordinate measuring machine. One-way analysis of variance (ANOVA) and paired t-test were performed at the significance level of 5%.

RESULTS

Gap distances of the cast implant bars after correction procedure showed no statistically significant difference among groups. Changes in bar length between pre-casting and post-correction measurement were statistically significance among groups. Axis angle changes of the right gold cylinders were not statistically significance among groups.

CONCLUSION

There was no statistical significance among three techniques in horizontal, vertical and axial errors. But, gas-air torch soldering technique showed the most consistent and accurate trend in the correction of implant bar error. However, Laser welding technique, showed a large mean and standard deviation in vertical and twisting measurement and might be technique-sensitive method.     

Technical validation of the Di3D stereophotogrammetry surface imaging system

The purpose of this work was to assess the technical performance of a three-dimensional surface imaging system for geometric accuracy and maximum field of view. The system was designed for stereophotogrammetry capture of digital images from three-dimensional surfaces of the head, face, and neck. A mannequin head was prepared for imaging by adding texture in the form of red paint, and facial landmarks as black ink dots. The mannequin was imaged at the manufacturer's recommended settings for human studies. Colour-coded surface difference images among repeated exposures were computed. We compared measurements of physical linear distance with digital measurements. The three-dimensional stereophotogrammetry system had a mean error in the three-dimensional surfaces of 0.057mm, a repeatability error (variance) of 0.0016mm, a mean error of 0.6mm in linear measurements compared with manual measurements, and a field of view of 170 degrees horizontally and 102 degrees vertically.     

A clinical technique for virtual articulator mounting with natural head position by using calibrated stereophotogrammetry

Accurate articulator-mounted casts are essential for occlusion analysis and for fabrication of dental prostheses. Although the axis orbital plane has been commonly used as the reference horizontal plane, some clinicians prefer to register the horizontal plane with a spirit level when the patient is in the natural head position (NHP) to avoid anatomic landmark variations. This article presents a digital workflow for registering the patient’s horizontal plane in NHP on a virtual articulator. An orientation reference board is used to calibrate a stereophotogrammetry device and a 3-dimensional facial photograph with the patient in NHP. The horizontal plane can then be automatically registered to the patient’s virtual model and aligned to the virtual articulator at the transverse horizontal axis level. This technique showed good repeatability with positional differences of less than 1 degree and 1 mm in 5 repeated measurements in 1 patient.     

Determination of facial symmetry in unilateral cleft lip and palate patients from three-dimensional data: technical report and assessment of measurement errors.

OBJECTIVE: To assess measurement errors of a novel technique for the three-dimensional determination of the degree of facial symmetry in patients suffering from unilateral cleft lip and palate malformations. DESIGN: Technical report, reliability study. SETTING: Cleft Lip and Palate Center of the University of Erlangen-Nuremberg, Erlangen, Germany. PATIENTS: The three-dimensional facial surface data of five 10-year-old unilateral cleft lip and palate patients were subjected to the analysis. Distances, angles, surface areas, and volumes were assessed twice. MAIN OUTCOME MEASURES: Calculations were made for method error, intraclass correlation coefficient, and repeatability of the measurements of distances, angles, surface areas, and volumes. RESULTS: The method errors were less than 1 mm for distances and less than 1.5 degrees for angles. The intraclass correlation coefficients showed values greater than .90 for all parameters. The repeatability values were comparable for cleft and noncleft sides. CONCLUSION: The small method errors, high intraclass correlation coefficients, and comparable repeatability values for cleft and noncleft sides reveal that the new technique is appropriate for clinical use.     

Three-dimensional facial anatomy evaluation: Reliability of laser scanner consecutive scans procedure in comparison with stereophotogrammetry

Laser scanner devices are acquiring a growing importance in facial anatomy. Most studies have analysed facial scans obtained through two simultaneous captures, whereas the same result can be obtained by consecutive three-dimensional (3D) scans. However, this latter procedure has not yet been validated.Fourteen volunteers underwent face image capture through stereophotogrammetry (VECTRA M3) and three consecutive facial scans through a laser scanner (Konica Minolta Vi910). The concordance between 14 linear distances, 12 angles, facial surface area and volume measurements was verified by the Bland–Altman test and calculation of absolute and relative technical errors of measurement (TEM/rTEM). The two facial images obtained by the different devices were then registered to calculate point-to-point distance.Most of linear distances and angles showed a high agreement, with “very good” or “good” rTEMs, ranging between 1.1% and 6.4%. Surface area measurements agreed well between the devices (rTEM: 6.3%), while volumes were poorly comparable (rTEM: 25.8%); the root mean square point-to-point distance was 0.80 mm (SD: 0.41).This study first tested the concordance of measurements on facial images obtained by stereophotogrammetry and consecutive laser scans. Results highlight the reliability of linear distances, angles and surface areas measurements, but discourage volume assessment and registration of surfaces acquired through different devices.