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.     

3D打印与带模铸造法制作的可摘局部义齿对患者主观感受的影响

目的: 比较3D打印与带模铸造法制作的可摘局部义齿对患者主观感受的影响。方法: 选择上海市口腔医院修复科门诊欲行可摘局部义齿修复的上颌Kennedy牙列缺损分类一类二亚类的牙列缺损患者80例,随机分为2组,分别按照3D打印法和带模铸造法制作可摘局部义齿。患者义齿完成初戴1周后复诊,观察记录患者口内黏膜压痛点的数量与部位,同时采用吸光度法进行咀嚼效率测定。义齿初戴完成2个月后,嘱患者复诊并发放调查问卷,分别对其主观感受及满意度进行调查。主观感受包括咀嚼效率、方便程度、固位效果、语言功能恢复、舒适程度、面容修复等6个方面。满意度评价包括治疗周期、治疗费用及治疗效果3个方面。采用SPSS 17.0软件包对结果进行统计学分析。结果: 在压痛点计数上,3D打印组少于带模铸造法组,而咀嚼效率则高于带模铸造法组,差别均有统计学意义(P<0.05);在主观感受及满意度方面,3D打印组高于带模铸造法组,差别有统计学意义(P<0.05)。结论: 3D打印法制作的可摘局部义齿在提高义齿的精度及患者使用舒适度方面具有一定优势。     

Digital Workflow for Producing Oral Positioning Radiotherapy Stents for Head and Neck Cancer

Oral positioning radiotherapy stents are devices that protect healthy structures adjacent to the target volume of head and neck radiotherapy treatment, leading to reduced acute and chronic side effects. This study describes a digital workflow to produce an oral positioning radiotherapy stent and analyze its efficacy by measuring dosimetric variations with and without this stent. An oral positioning radiotherapy stent was created according to a digital workflow that included intraoral scanning, digital design, and 3D printing for a patient with squamous cell carcinoma of the tongue. The patient underwent computed tomography to evaluate radiotherapy treatment by intensity‐modulated radiation therapy with and without the use of the 3D‐printed oral stent. The use of a 3D‐printed oral positioning radiotherapy stent is a feasible and reproducible technique that reduced the planning target volume and radiation doses delivered to the hard palate, right parotid gland, and left parotid gland by 42%, 21%, and 8.5%, respectively.     

3D打印钴铬合金和铸造钴铬合金的理化性能和生物相容性的比较

目的 比较3D打印和传统铸造钴铬合金的理化性能及生物学影响.方法 实验组和对照组分别用3D打印技术中的选择性激光熔融(SLM)和传统铸造技术,制作钴铬合金试件各10个,采用洛氏硬度计HR-150A和金相显微镜对两组分别进行洛氏硬度测定和金相观察,并在自腐蚀电位下对金属试件进行极化曲线测定.在无菌环境下制备试件的浸提液,...     

Generation of 3D digital models of the dental arches using optical scanning techniques

Due to a number of benefits mainly concerning orthodontic treatment planning and issues of documentation and sharing of patient records, digital models of the dental arches are more and more replacing conventional stone models in clinical orthodontics. To date, the most common approach for generating digital models of the dental arches comprises the digitization of stone models mostly by using optically-based desktop scanner systems. This indirect approach is sufficiently accurate and achieves a largely complete model surface with relatively low equipment acquisition costs. In the recent decade, however, intraoral scanners are becoming ever more established and proven in clinical practice. The great advantage of this direct approach for generating digital models is that the intermediate step of stone cast fabrication can be omitted which eliminates material and space requirements for casts. The various commercially available intraoral scanning systems are based on the application of different optical measurement techniques. Fringe (i.e., structured-light) projection and two or more camera systems lead to a bulky arrangement and to shadowing effects which limit the accessibility of undercuts and thin volume fractions such as incisal edges. Moreover, they usually require powder coating of the teeth. Confocal laser scanners eliminate these disadvantages, although the three-dimensional (3D) movement of the scanner handpiece is disadvantageous with regard to scanning speed, accuracy and reliability. Intraoral scans generally contain a source of risk for inaccuracy, because multiple single 3D images are assembled to a complete model. Recent studies, however, have shown that the trueness and precision of intraoral scanners of commercially available scanning systems is already sufficient for orthodontic applications. Current development of novel scanner technologies, e.g. based on multipoint chromatic confocal imaging and dual wavelength digital holography, will further improve the accuracy and clinical practicability of intraoral scanning. Hence, it is likely that in future intraoral scanning combined with 3D printing will completely replace conventional stone models of the dental arches.     

骨组织工程3D生物打印的研究进展

近几十年来,骨组织工程在骨缺损修复治疗的应用中获得了飞速的发展,而3D生物打印是近十年来在骨组织工程中一种非常具有前景的技术.传统骨组织工程支架制造方法无法精确控制空间结构,且在支架制作完成后接种细胞也无法控制细胞的均匀分布.尽管3D生物打印作为一类含细胞骨组织工程支架制造技术,以水凝胶类材料作为基础将细胞置入支架中,...     

Accuracy of removable partial denture framework fabricated by casting with a 3D printed pattern and selective laser sintering

PurposeThe present study aimed to compare the accuracy of removable partial denture (RPD) frameworks fabricated by 3D-printed pattern casting and those fabricated by selective laser sintering (SLS).MethodsA partially edentulous mandibular model was used for the simulation model. Scanning of the model was performed using a dental scanner. The framework was designed by using CAD software. The 3D-printed resin pattern was formed using a 3D printer and casting was performed (AM-Cast framework), and a direct metal laser sintering machine was used for the framework of SLS (SLS framework). 3D scanning of fabricated two types of framework were performed, and these data were overlapped with design data. Fabrication accuracy was verified using the Mann–Whitney U test to compare the discrepancy between the AM-Cast and SLS frameworks.ResultsThe range of differences for the AM-Cast and SLS framework were −0.185 ± 0.138 to 0.352 ± 0.143 mm and −0.166 ± 0.009 to 0.123 ± 0.009 mm, respectively. Statistically significant differences were observed at the rests, proximal plates, connectors, and clasp arms. Regarding the rests, both lateral and medial displacement in the two types framework was observed in relation to the design data. Large lateral discrepancies of the connectors were observed at the joining area on the tooth-supported side of the lingual bar for the AM-Cast framework. Localized discrepancies were observed at the center of the lingual bar for the SLS framework.ConclusionThe accuracies of RPD frameworks fabricated by AM-Cast and SLS differ depending on the specific structural component of the RPD.     

Partially digital workflow for making complete-arch implant-supported fixed prostheses: A dental technique

This article describes a technique for making complete-arch implant-supported fixed prostheses by using intraoral scanning and computer-aided design and computer-aided manufacturing (CAD-CAM) technology for the fabrication of a metal substructure and conventional processing for the prosthesis base. For this, a device was designed to accurately capture the position of multiple implants and the associated digitalized surgical guide, and the metal substructure was planned and milled directly in cobalt-chromium. The color of the gingiva and artificial teeth was selected by using the intraoral scanner software program, and the prosthesis base was processed conventionally. The straightforward methods used to fabricate the prostheses eliminated possible errors associated with conventional substructure casting and occlusal registration.     

Accuracy of CAD-CAM systems for removable partial denture framework fabrication: A systematic review

Statement of problemRemovable partial dentures (RPDs) are traditionally made by casting, a complex, error-prone, and time-consuming process. Computer-aided design and computer-aided manufacturing (CAD-CAM) RPD systems may simplify the clinical steps and minimize errors; however, the accuracy of CAD-CAM RPD systems is unclear.PurposeThe purpose of this systematic review was to determine whether CAD-CAM systems are accurate for the manufacturing of RPD frameworks.Material and methodsA literature search was conducted through Medline-PubMed, Scopus, Lilacs, Web of Science, and Cochrane Library databases using specific keywords for articles published up to November 2019. Three reviewers obtained data and compared the results. All studies evaluated the framework accuracy or fit of prostheses fabricated with conventional and digital techniques.ResultsA total of 7 articles, 2 clinical studies, and 5 in vitro studies that complied with the inclusion criteria were evaluated. One in vitro study compared indirect (extraoral) and direct (intraoral) scanning for partially edentulous ridges and shows that digital scans were better than conventional impressions in terms of trueness. In the other studies included, although the frameworks analyzed had clinically acceptable discrepancies (<311 μm), the material influenced the fit. Polyetheretherketone (PEEK) showed better fit than traditional metal cast RPDs. Co-Cr alloy RPDs produced by rapid prototyping exhibited the highest discrepancies when produced by sintering laser melting.ConclusionsThe results show that the digital technique for RPD frameworks is accurate. In the studies included, the analyzed frameworks had clinically acceptable gaps, but the results were heterogeneous among studies because the articles used different measurement methods with small sample sizes. Few studies discussed the long-term clinical performance. The digital technique for RPD frameworks was accurate because the misfits and mismatches found in in vitro and clinical studies were within the acceptable clinical limit for RPDs.     

CAD/CAM切削技术在可摘局部义齿支架制作中的应用

目的探讨计算机辅助设计与制作（CAD/CAM）切削技术在可摘局部义齿（RPD）支架制作中的临床应用效果。 方法选取2017年9月至2018年6月南京市口腔医院修复科就诊的Kennedy Ⅰ类牙列缺损患者共26例，采用随机数字表法分为传统方法组和CAD/CAM组，每组13例。常规制取精细印模，其中CAD/CAM组通过扫描石膏模型获取三维数据，CAD RPD支架形态，CAM切削生成支架树脂铸型，常规包埋铸造完成RPD金属支架。传统方法组以常规方法制作支架蜡型，包埋铸造完成RPD支架。临床试戴，比较两种金属支架就位情况，与口内软硬组织的密合度。采用秩和检验的独立样本Mann-Whitney检验进行统计分析。 结果传统方法组制作的RPD支架9例就位顺利，4例经少量调磨就位，而CAD/CAM组制作的RPD支架10例顺利就位，3例经少量调磨就位。两组RPD支架均无大量调磨仍无法就位的现象发生，就位情况间差异无统计学意义（U = 78.0，P = 0.5）。2组患者中均有12例支架密合，1例支架存在≤3处不密合部位的现象，密合情况之间差异无统计学意义（U = 84.5，P = 0.760）。 结论CAD/CAM切削支架蜡型制作的RPD金属支架修复效果可以达到临床要求。     

颅颌面修复体制作用3D打印金属粉末的研究进展

随着3D打印的快速发展,其在口腔颅颌面外科的应用越来越广泛,3D打印个性化生产改变了传统依靠手工成型的落后模式,满足了不同患者的使用需求。但目前对于颅颌面修复体制作用3D打印金属粉末的性能要求并无明确规范,不利于产业的长久发展。本文对颅颌面修复体制作用3D打印金属粉末的制备工艺（气雾化法、等离子体旋转电极雾化法、射频等离子体球化法）以及3D打印成型工艺（选区激光熔化、电子束选区熔化、激光近净成形）进行了介绍,并且根据制备工艺及成型工艺特点总结了颅颌面修复体制作用3D打印金属粉末的性能要求。     

颅颌面修复体制作用3D打印金属粉末的研究进展

随着3D打印的快速发展,其在口腔颅颌面外科的应用越来越广泛,3D打印个性化生产改变了传统依靠手工成型的落后模式,满足了不同患者的使用需求。但目前对于颅颌面修复体制作用3D打印金属粉末的性能要求并无明确规范,不利于产业的长久发展。本文对颅颌面修复体制作用3D打印金属粉末的制备工艺（气雾化法、等离子体旋转电极雾化法、射频等离子体球化法）以及3D打印成型工艺（选区激光熔化、电子束选区熔化、激光近净成形）进行了介绍,并且根据制备工艺及成型工艺特点总结了颅颌面修复体制作用3D打印金属粉末的性能要求。     

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。     

Non‐Radiological Method for Fabrication of a Screw‐Channel Drilling Guide in Cement‐Retained Implant Restorations Using Intraoral Digital Scanning and Imaging Superimposition: A Clinical Report

The difficulty of retrieving the abutment screw is a major disadvantage of cement‐retained implant restorations. Conventional methods for locating the screw‐access hole are based largely on radiography or manual labor, which limits accuracy and clinical feasibility. This clinical report describes a non‐radiological method for fabricating an accurate drilling guide for location of the screw channel using intraoral optical scanning, 3D superimposition, and computer‐aided design and computer‐aided manufacturing (CAD/CAM) technologies. The present technique not only improves the guide fabrication process and the accuracy of screw‐channel drilling, but also has wide indications for implant restorations.     

Implementation of 3D technologies in the workflow of auricular prosthetics: A method using optical scanning and stereolithography 3D printing

The fabrication of auricular prostheses is traditionally time consuming, and the definitive esthetic appearance is highly skill dependent. A method of creating the wax pattern for an auricular prosthesis by using optical scanning and 3D printing is described. A digital scan of the unaffected ear is used for computer-aided design and manufacturing of a mold for casting the wax pattern of the prosthesis. The process is efficient and increases the predictability of the esthetic outcome.     

可摘局部义齿支架的计算机辅助设计与快速制造

目的 自主开发可摘局部义齿支架三维设计软件及选择性激光熔融制造(selective laser melting,SLM)设备,探讨应用其进行可摘局部义齿支架设计并直接成形金属支架的方法 .方法 使用层析扫描仪获得两个牙列缺损模型的三维点云数据.使用自主开发的可摘局部义齿支架三维设计软件进行模型观测及可摘局部义齿支架(牙合)支托、卡环、舌杆、金属加强网、上颌大连接体等组件的设计.组件设计路线:首先确定组织面轮廓,利用轮廓线内的点云数据生成组织面.根据各个组件的特点,设定抛光面截面形态,结合轮廓线生成抛光面.各组件完成后,用小连接体连成完整支架.将完成的支架数据导入SLM设备中,直接成形金属支架.结果 应用自主开发的可摘局部义齿支架三维设计软件及SLM设备,成功进行了两个可摘局部义齿金属支架的计算机辅助设计及快速制造,在模型上试戴后目测金属支架适合性良好.结论 自主开发的具有完全自主知识产权的可摘局部义齿支架计算机辅助设计与辅助制作系统,可为可摘局部义齿金属支架的制作提供一种新的方法.     

Digital fabrication of a maxillary obturator prosthesis by using a 3-dimensionally–printed polyetheretherketone framework

The digital fabrication of a maxillary obturator with a 3D-printed polyetheretherketone (PEEK) framework is described. Digital oral data were scanned for the computer-aided design (CAD) of the framework and the 3D printing of a preliminary resin cast. The framework was accurately printed from a PEEK filament material. A secondary impression was made to fabricate the definitive cast. The PEEK framework exhibited precise fit, excellent retention, and reduced weight compared with a typical metal framework.     

口腔修复用金属三维打印件中夹杂物和孔隙率问题分析

目的 探讨口腔修复用金属三维打印件中夹杂物和孔隙率不合格原因，为三维打印口腔金属修复体的加工制作过程控制提供参考。方法 选择44批次钴铬合金和钛合金激光选区熔化（SLM）修复体3D打印件，在金相显微镜下放大100倍测定夹杂物和孔隙的面积分数，分析打印件的孔隙特征和产生不合格的原因。结果 夹杂物和孔隙的面积分数>2.8%的有16批次，不合格率为36.4%。44批次检测样品中未见明显夹杂，不合格均由孔隙面积分数超过2.8%导致。结论 目前口腔修复体加工制作行业对数字化3D打印技术的掌握尚不成熟，加工工艺技术有待进一步提高。     

Enhancing Student Learning of Removable Prosthodontics Using the Latest Advancements in Virtual 3D Modeling

When educating dental students or prosthodontic residents, a picture can be worth a thousand words. If that is so, then what could enhanced 3D modeling be worth relative to enhancing student learning? The answer is undoubtedly more than what a picture can provide. That is why the use of 3D models has become increasingly common with respect to patient care. The 3D modeling allows the patient to visualize more clearly the proposed treatments and outcomes; however, while 3D modeling has started to make an appearance in dental education, many of the current 3D modeling techniques do not offer the flexibility needed for dental education and enhanced student learning. At the University of Iowa, the use of 3D modeling software has enabled the creation of 3D models that can be altered or customized to be used in a more flexible way to teach students in the arts and complexities of removable partial denture (RPD) design and associated components. This educational technique article will: (1) demonstrate how these 3D models can be used to enhance student perception and learning regarding RPDs; and (2) will demonstrate using videos and web‐based portals to show how the 3D RPD models were created and then used for educational purposes.