牙冠外形三维光学测量系统标定实验(一)-- 误差消除和标定曲线获得

消除牙冠外形三维光学测量系统的系统误差和位相分布测量计算误差。方法：用冠冠外形三维光光学测量系统测量标准石膏模型,确定位相分布与该石膏模型表面高度的关系。结果得到一个位相－高度映射关系曲线。     

牙冠外形三维光学测量系统标定实验(二)--位相-高度转换实验

目的：验证牙冠外形三维光学测量系统标定实验（一）的结果。方法：用牙冠外形三维光学测量系统测量标准圆柱状石膏模型，将测量得到的位相值转成该石膏模型表面高度值。结果：得到标准圆柱状石膏模型表面实际高度图，比较准确地反映出了被测量圆柱标准试件的高度。结论：所采取标定实验简单实用。     

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。     

牙冠三维演示模型建立方法的探讨

目的：初步探讨基于普通Windows平台的牙冠三维演示模型建立的方法。方法：通过获取牙冠石膏模型三轴外形轮廓及He龈向层面截面外形，在Windows98下，利用3Dmax软件重建牙冠三维模型。结果：寻求了一套简单、价廉、易操作的牙冠三维教学演示模型建立的方法。结论：该牙冠建模方法简单易行，可应用于实验课教学；建立的牙冠模型可供教学演示，网络教学，多媒体制作，为修复体设计三维预览奠定基础。     

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。     

无托槽隐形矫治数字化模型及软件测量系统的准确性研究

目的 探讨国产无托槽隐形矫治客户端软件中基于工业CT重建的数字化模型及测量系统的准确性.方法 选择无托槽隐形矫治患者的初诊石膏模型20副,以及对应的无托槽隐形矫治公司提供的三维数字化模型20副.分别采用手工测量石膏模型,及软件测量系统测量数字化模型,测量项目包括牙冠宽度、临床牙冠高度、牙弓宽度、牙弓长度、(牙合)覆盖六项指标.采用组内相关系数(ICC)对重复测量信度进行评估;采用多变量假设检验(Hotelling T2检验)分析数字化模型及石膏模型的总体测量结果有无差异,并采用配对t检验分析两种模型测量方法在各测量指标上有无差异.结果 软件测量数字化模型的组内相关系数为0.958,优于手工测量石膏模型0.933.两种模型的总体测量结果无统计学差异(P＞0.05).在具体测量指标中牙冠宽度,牙弓长度,牙弓宽度无统计学差异(P＞0.05),而临床牙冠高度(P＜0.01)、覆(牙合)(P＜0.05)、覆盖(P＜0.05)有统计学差异.结论 无托槽隐形矫治软件测量系统中数字化模型及测量系统的准确性较高.     

光栅投影技术及逆向工程在重建和测量牙颌数字化模型中的应用

目的 利用光栅投影技术采集数字化牙颌模型并用逆向工程分析测量模型特征,为建立正常牙列数字化模型数据库奠定基础。方法 在计算机控制下将光栅投影在正常牙颌模型上,通过多角度拍摄模型获得三维数据外形轮廓,利用逆向工程重建数字化模型和测量分析牙列形态特征,并与石膏模型测量结果进行对比分析。结果 重建的三维数字化模型结构清晰。数字化模型的两次测量结果无统计学差异（P>0.05）;数字化模型与石膏模型的测量指标中,牙冠长度和牙弓宽度均无统计学差异（P>0.05）,而牙冠宽度和牙弓长度均有统计学差异（P<0.05）。结论 通过光栅投影技术以及逆向工程重建数字化模型,可用于临床、科研中的牙颌模型测量,为建立正常牙颌数字化模型数据库提供科学方法。     

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。     

激光扫描在面部畸形三维重建及测量中的初步应用

目的开发建立一套面部三维结构重建、测量及诊断分析系统。方法应用系统建立标准石膏立方体试件以及石膏头像三维计算机模型并进行定点、测量,测量值与标准值比较获得系统建模误差以及定点误差范围;2例面部畸形患者进行了面部三维扫描建模,应用系统对患者面部计算机模型进行了定点、线距、角度测量以及初步对称性分析。结果三维计算机模型的建模误差在0.2 mm以内,定点误差在0.5 mm以内。应用本系统可以完成三维计算机模型的定点、线距、角度测量及对称性分析工作,基本能够达到临床要求。结论三维激光扫描技术为颌面部畸形患者面部软组织三维结构重建和非接触式测量提供了一种简便、精确、高效的方法。     

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。     

牙冠表面形状测量造型方法

目的：建立牙冠测量造型方法,为修复体ＣＡＤ／ＣＡＭ实现奠定基础。方法：采用自制的牙冠表面形状三维测量仪和精密可调转台获得测量数据,在ＵｎｉＧｒａｐｈｉｃ软件平台上针对牙冠造型进行二次开发,通过旋转坐标轴的方法实现牙冠各面数据拼合,生成牙冠实体模型。结果：获得了上颌中切牙和下颌磨牙的计算机数据模型,逼真地再现了它们的形态。结论：牙冠测量造型方法可行。     

面部软组织三维测量系统的可靠性研究

目的检验面部软组织三维测量系统的技术可靠性.方法以石膏头像为研究对象,用系统在15种不同条件下测量模型面部9个点至鼻根点的距离,以用游标卡尺得到的测量结果为评判标准与前者比较.结果两者的平均差值为1.21mm,误差率为2.08%.模拟头位变化的8种状态中,仅在右转10°时与标准相比有显著性差异.结论系统的测量误差达到人体测量手册的要求.     

Validation and reproducibility of a high-resolution three-dimensional facial imaging system

OBJECTIVE: To assess the accuracy and reproducibility of a high-resolution three-dimensional imaging system (Di3D). DESIGN: The three-dimensional imaging system was validated in vitro using 12 adult facial plaster casts, which had landmarks marked, and the positions of the landmarks on the three-dimensional images captured by Di3D were compared with those obtained by a coordinate measuring machine (CMM). METHODS: Operator error was measured by repeatedly locating landmarks on the three-dimensional image. Reproducibility error of the images was calculated by capturing three-dimensional images of the facial casts on two separate occasions; the Euclidean distance between the two matched sets of coordinates was then calculated. The Di3D system error was assessed by calculating the three-dimensional global positions of landmarks on the three-dimensional images and comparing them with those obtained by CMM (gold standard). RESULTS: The operator error in placement of landmarks on the three-dimensional model was 0.07mm, range 0.02-0.11mm. The reproducibility of the Di3D capture was 0.13mm, range 0.11-0.14mm. The mean distance between the CMM and Di3D landmarks, which constitutes the Di3D system error, was an average of 0.21mm, range 0.14-0.32mm. CONCLUSIONS: The Di3D system error was within 0.2mm, which is clinically acceptable, and offers considerable improvement in stereophotogrammetry for facial capture and analysis.     

Validation of a vision-based, three-dimensional facial imaging system.

OBJECTIVE: The aim of this study was to assess the accuracy of a newly developed three-dimensional (3D) imaging system in recording facial morphology. METHODS: Twenty-one infants with cleft lip each had a full-face alginate impression taken at the time of primary lip repair, and a stone cast was constructed from each impression. Five anthropometric points were marked on each cast. Each cast was digitized, and the 3D co-ordinates of the five points were obtained using a co-ordinate measuring machine (CMM, Ferranti) of documented accuracy (9.53 microm). Each cast was scanned in four positions using a computerized stereophotogrammetry (C3D) system. The five points were located on the 3D images, and their 3D co-ordinates were extracted by three operators. The co-ordinate systems produced by C3D were aligned, via translation and rotation, to match the CMM co-ordinate system using partial ordinary procrustes analysis. The displacements of the adjusted C3D co-ordinates from the reference co-ordinates were then measured. Three different types of errors were identified: operator, system, and registration errors. RESULTS: Operator error was within 0.2 mm of the true co-ordinates of the landmarks. C3D was accurate within 0.4 mm. The average displacement of points over the 21 casts at four positions for the three operators was 0.79 mm (median 0.68). CONCLUSIONS: The presented 3D imaging system is reliable in recording facial deformity and could be utilized in recording cleft deformities and measuring the changes following surgery     

Palatal surface area of maxillary plaster casts--a comparison between two-dimensional and three-dimensional measurements.

OBJECTIVE: To investigate the relationship between corresponding two-dimensional and three-dimensional measurements on maxillary plaster casts taken from photographs and three-dimensional surface scans, respectively. MATERIALS AND METHODS: Corresponding two-dimensional and three-dimensional measurements of selected linear distances, curve lengths, and (surface) areas were carried out on maxillary plaster casts from individuals with unilateral or bilateral cleft lip and palate. The relationship between two-dimensional and three-dimensional measurements was investigated using linear regression. RESULTS AND CONCLUSIONS: Error sources in the measurement of three-dimensional palatal segment surface area from a two-dimensional photograph were identified as photographic distortion (2.7%), interobserver error (3.3%), variability in the orientation of the plaster cast (3.2%), and natural shape variation (4.6%). The total error of determining the cleft area/palate surface area ratio was 15%. In population studies, the effect of using two-dimensional measurements is a decrease of discriminating power. In well-calibrated setups, a two-dimensional measurement of the cleft area/palate surface area ratio may be converted to a three-dimensional measurement by use of a multiplication factor of 0.75.     

不同膨胀系数石膏模型材料对树脂义齿表面粗糙度的影响研究

目的研究不同膨胀系数石膏模型材料对义齿表面粗糙度的影响。方法采用高、中、低三种不同膨胀系数的石膏模型材料,分别装埋型盒,各制作5个30 mm×10 mm×6.0 mm的树脂基托试样,测量其表面粗糙度。结果高、中、低膨胀系数石膏模型材料制作树脂试样表面粗糙度:轮廓算术平均偏差(Ra)值分别为(1.64±0.23)μm,(1.08±0.13)μm,(0.65±0.23)μm;微观不平高度(Rz)值分别为(6.44±1.12)μm,(5.18±0.96)μm,(3.35±0.95)μm,差别有统计学意义(P<0.01)。结论低膨胀系数石膏模型材料制作的树脂试料表面粗糙度值最低。