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。     

下颌牙列缺损患者可摘局部义齿铸造支架的计算机辅助设计

目的对20例临床下颌牙列缺损患者可摘局部义齿支架进行三维计算机辅助设计。方法光栅投影测量法获取20例下颌牙列缺损患者石膏模型的三维数据,按照临床设计原则,利用3DMax、Geomagic和RapidForm等软件分别构建卡环、支托、舌杆、舌板和加强网等可摘局部义齿支架各部件的三维数字化模型,组合完成可摘局部义齿支架的计算机辅助设计,并构建了支架及其部件数据库。结果成功构建了20例临床患者下颌可摘局部义齿的个性化计算机三维支架模型。结论通用三维设计软件可以实现个性化支架的计算机辅助设计。     

可摘局部义齿

套筒冠可摘活动义齿修复后出现的问题及处理；上颌可摘局部义齿修复对辅音声学特征的影响；上颌肯氏Ⅰ类牙列缺损义齿修复对元音的影响；牙列缺损患者三维数字化牙颌模型数据库的建立。     

可摘局部义齿支架几何模型的设计

目的:利用国产CAD/CAM软件系统,通过对可摘局部义齿支架的计算机辅助设计,探索开发适用于口腔修复专业义齿设计与数控加工制作的国产软件系统。方法:投影光栅测量法获取下颌KennedyⅡ类2亚类牙列缺损石膏模型的点云数据,在国产CAD/CAM系统中,进行数据精简,并在此点云数据基础上,确立观测线和就位道。按照临床设计原则,分别构建卡环、支托、舌杆、加强网等支架各部件的组织面与磨光面,包括舌杆的半梨形截面、加强网的内外终止线和组织终止点等特征性结构的构建,完成支架的三维几何模型计算机辅助设计。结果:成功建立了可摘局部义齿支架的几何模型。该模型可视性强,便于修改,支架与牙颌模型密合良好。模型的输出数据文件格式为STL,这种通用的传输格式有利于后续的计算机辅助制作。结论:基于国产CAD/CAM软件系统进行可摘局部义齿支架几何模型的设计是可行的。     

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。     

可摘局部义齿计算机辅助设计三维图像专家系统的研究

目的开发可摘局部义齿计算机辅助设计三维图像专家系统。方法运用表面绘制法依据CT扫描头颅骨标本在3DStudioMax中重建模拟牙列缺损的牙颌三维模型,以此模型为平台,建立图形库和知识库,制作人机对话操作界面和专家系统安装文件,开发出可摘局部义齿修复计算机辅助设计三维图像专家系统。结果成功研制一套牙列缺损可摘局部义齿修复计算机辅助设计三维图像专家系统。结论该专家系统具有逼真的三维图像效果,为可摘局部义齿的进一步开发奠定了基础。     

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。     

可摘局部义齿铸造支架铸型CAD/CAM技术的临床初步应用研究

目的通过对临床KennedyⅠ类上颌牙列缺损患者进行可摘局部义齿支架的计算机辅助设计与制作,为进一步开发适用于口腔临床的可摘局部义齿CAD/CAM技术奠定基础。方法选择临床病例KennedyⅠ类患者,常规牙体制备、模型观测、模型处理,投影光栅测量法获取工作模型以及对颌模型三维数据。在CATIA等软件中,按照临床设计要求分别完成卡环、支托、腭杆、加强网等支架部件的三维建模,最终连接为支架数字化模型,再将保存为三角网格数据STL格式的支架数据导入快速成型设备中,加工获得树脂铸型,常规包埋、铸造获得钴铬合金支架,在临床上进行口内试戴。结果初步完成1例临床病例可摘局部义齿铸造支架的CAD/CAM。结论运用工程软件,计算机辅助设计以及快速成型技术可以初步设计、制造出适用于口腔临床的可摘局部义齿铸造支架。     

牙列缺损数字化模型观测方法初探

目的 探索牙列缺损数字化模型的观测方法,为下一步计算机辅助设计(CAD)可摘局部义齿支架奠定基础.方法 三维点激光扫描仪采集牙列缺损石膏模型的三维点云数据,在国产三维CAD软件唐龙系统中进行数据处理和三维重建.以唐龙系统为平台,用C++语言开发"模型观测"功能模块.在点云中心建立垂直于胎平面的中心轴,以10°为单位,将周围点云围绕中心轴等分为多个区域,通过计算每个区域内点云距中心轴的距离,得到颊、舌侧外形高点,分别连接每个区域颊侧及舌侧外形高点,得到以中心轴方向为就位道的观测线.通过调整中心轴角度得到不同的观测线.唐龙系统在生成观测线的同时自动标示倒凹区,并测量倒凹深度,通过将外形高点线沿就位道方向向倒凹区延伸完成去除倒凹的功能.结果 在计算机中绘制出牙列缺损数字化模型的观测线,确定了倒凹区及倒凹深度,并可完成去除倒凹的操作.数字化模型的观测线与传统方法在石膏模型上绘制的观测线形态相似.结论 基于唐龙系统开发的"模型观测"模块可实现对牙列缺损数字化模型的观测,操作简便,可在此模块基础上进一步进行可摘局部义齿CAD.     

牙列缺损模型三维数字化观测线的确立

目的 探索一种基于三维点云模型获取三维数字化观测线的计算方法,开发自动提取三维数字化观测线的软件,为提高模型观测的客观性和精确度、实现应用计算机辅助设计(CAD)与计算机辅助制作(CAM)技术完成可摘局部义齿修复奠定基础.方法以Kennedy第二类第二亚类牙列缺损为研究对象,光栅扫描法采集石膏模型的三维点云数据,在Geomngic Studio 6通用CAD-CAM软件中进行数据处理和三维重建.通过本项实验开发的投影轮廓提取法软件,计算观测方向上的最大轮廓曲线,测量倒凹深度,确定并标记卡环固位体卡臂尖的位置.结果得到牙列缺损模型的三维数字化观测线;该观测线将倒凹区和非倒凹区明确分开,可从各个方向观察和分析模型,判定相应的义齿就位道;自动测量倒凹深度,确立并标记固位臂卡臂尖的位置.结论应用该计算方法和软件初步实现了牙列缺损三维模型的数字化观测和分析.     

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。     

A digital approach to the evaluation of mandibular position by using a virtual articulator

The purpose of this technique report was to describe a fully digital technique to evaluate the mandibular position both in centric relation occlusion (CRO) and maximal intercuspation position (MIP). The procedure transfers data relative to the position of the maxillary and mandibular dentition to a virtual articulator based on a single cone beam computed tomography (CBCT) image. A CBCT scan of the patient was obtained in CRO, and the maxillary and mandibular casts were scanned both in CRO and MIP with an intraoral scanner. The model CRO scan data were registered on the dental part of the CBCT image by using a virtual articulator program, and a virtual facebow transfer process and mounting was performed. The virtual articulator was positioned in the right and left condyle medial pole and right orbitale. The mandibular position was evaluated in CRO and MIP by superimposing the data of the mandible position in both CRO and MIP. A quantitative 3D measurement was obtained by using the grid function. Based on this protocol, it is possible to use a fully digital approach to transfer the position of a patient’s maxillary dentition to a virtual articulator based on the data from a single CBCT scan and intraoral scans. This technique eliminates the traditional facebow transfer and mounting process and complicated laboratory procedures for evaluating mandibular positional changes in CRO and MIP.     

Evaluation of senior Brazilian dental students about mouth preparation and removable partial denture design

This study aimed to evaluate the knowledge of senior dental students about mouth preparation and removable partial denture (RPD) design. Two hundred sixty-six senior students from eleven dental schools in the State of S?o Paulo, Brazil, comprised the sample. The subjects examined two partially edentulous casts mounted on a semiadjustable articulator, answered a questionnaire regarding the treatment plan, and drew the RPD design. The casts consisted of Kennedy Class III, modification 1 maxillary arch and Class II mandibular arch. Ninety percent of the students believed that mouth preparation should be performed although no one was able to name all necessary procedures. For the maxillary arch, 12 percent of the denture designs were completely appropriate, 51 percent were partially appropriate, and 37 percent were inappropriate. For the mandibular arch, the results were 3 percent, 40 percent, and 57 percent, respectively.     

Change in dentition over 20 years from third decade of life

PurposePrevious studies have documented long-term, age-related change in the teeth, dental arches and occlusion. However, very few studies have investigated longitudinal age-related change in the dentition using 3-dimensional (3-D) measurement. The purpose of this study was to clarify age-related change in the dentition using a laser scanner.Materials and methodsWe used dental casts obtained from the same subjects in their twenties and forties. Subjects were selected based on near-normal occlusion. We investigated age-related variation in the dentition using 3-D measurement.ResultsAge-related change in the dentition was characterized by a decrease in maxillary and mandibular width, an increase in maxillary length, and a decrease in mandibular length. Measurement of angulation revealed that the maxillary canines and molars were mesially inclined. We observed labial inclination of the maxillary incisors, and lingual inclination of the mandibular incisors, as well as the maxillary and mandibular canines and molars. Overjet, overbite, and the irregularity index all showed an increase, while occlusal vertical dimension showed a decrease. Multiple regression analysis indicated that lingual inclination of the lower central incisors was related to an increase in the irregularity index, and that lingual inclination of the upper canines and decrease in occlusal vertical dimension of the anterior teeth were related to increased overbite.ConclusionThe present findings showed that age-related changes in angulation and inclination of each tooth should be taken into account when providing occlusal rehabilitation or post-orthodontic retention.     

Early treatment with rapid palatal expander and 3D Quad Action mandibular appliance: evaluation of a comprehensive approach in 22 patients

The aim of this retrospective study in mixed dentition was to quantify dental arches and radiographic changes with a rapid maxillary expander followed by a transpalatal bar with arms and a 3D Quad action mandibular appliance, at the end of the treatment (T1) and six months afterwards (T2). MATERIAL AND METHODS: Thirty Class II patients in mixed dentition with tooth size-arch length discrepancies were studied (22 treated). We obtained measurements from dental casts before treatment, at T1 and T2 and radiographic changes at T1. The breathing was appraised. RESULTS: We found a significant (p < 0.05) increase of maxillary (+7.41 mm) and mandibular (+2.96 mm) dental arch perimeter, of intercanine gingival width (maxillary +3.25 mm, mandibular +1.57 mm) and of intermolar gingival width (maxillary +5.32 mm, mandibular +2.32 mm). There is a statistically significant increase of SNB angle. All posterior cross bites were corrected. We obtained a better position for the maxillary canine on radiography. All patients had nasal breathing at T1. Non treated subjects showed no improvement. In conclusion, this interceptive treatment corrected posterior cross bites, improved breathing and suggests an amelioration of tooth size-arch length discrepancy.     

Factors affecting soft tissue around dental implants: a review of the literature

Much of the focus in the early dental implant literature is on the bone-to-titanium interface because a successful osseointegrated implant requires direct bone contact to the implant surface. The research on soft tissue around dental implants has focused on the partially edentulous patient and, in particular, on the maxillary anterior dentition. Few studies have evaluated soft tissue around dental implants in completely edentulous patients over time. This paper reviews the pertinent literature on soft-tissue healing in both partially and completely edentulous dental implant patients from a Medline search of the English peer-reviewed literature from 1980 to 2004.     

Degeneration of tooth germ in the developing dentition of the gray short-tailed opossum (Monodelphis domestica)

The aim of this study was to examine the developmental aspects of the dental lamina and the tooth germ of the marsupial opossum (Monodelphis domestica), and to clarify the dental formula of this animal. Specimens were 12-, 16-, and 18-d-old opossums. 3-D reconstructions were constructed from frontal serial sections. In these animals, the tooth germs of the deciduous maxillary and mandibular canine, deciduous third premolar and first molar, and the deciduous maxillary first incisor and second molar had a successional dental lamina and a replacement tooth germ. The tooth germ of the deciduous maxillary fourth incisor and the mandibular first incisor were reduced. The dental lamina was continuous in each jaw except for the deciduous maxillary first incisor. The first dentition (deciduous dentition) remained as the permanent dentition on the deciduous maxillary first incisor, and the deciduous maxillary and mandibular canine and first molar. The maxillary fourth incisor and the mandibular first incisor were the second dentition (successional dentition). Only the deciduous third premolars were replaced. These results showed monophyodonty caused by both deciduous and replacement tooth germ degeneration.     

自锁托槽与传统金属托槽扩弓效果的对比研究

目的：评价自锁托槽与传统托槽在牙齿排齐阶段上颌牙弓形态的变化。方法：选取我院就诊的轻中度拥挤病人使用自锁和MBT金属托槽各15例,排齐后,取上颌阶段模型,所有模型用3DSS三维扫描仪扫描,并用Geomagics10.0图像处理软件建立数字化模型,然后选取牙弓标志点进行测量,应用SPSS17.0统计软件进行分析两组间治疗前后的牙弓长度,牙弓宽度等的变化。结果：排齐前后自锁组和MBT组在牙弓前段宽度和牙弓前段长度的比较都有显著性差异,在基骨宽度和长度以及磨牙的宽度上无统计学差异。在牙弓中段宽度的增加上自锁组明显多于MBT组,增加了（0.89±1.22）mm,MBT组治疗前后变化无统计学差异。结论：对于轻中度拥挤的患者,牙齿排齐后,自锁托槽和传统直丝托槽都能使牙弓宽度和长度有不同程度的增加,唇倾度增大,但两组间的前后变化的差值没有显著性差异,也就是说自锁托槽无治疗结果上的优势。