Current status and applications of 3D scanning in dentistry

Craniofacial identification standards: A review of reliability, reproducibility, and implementation

There are numerous anatomical and anthropometrical standards that can be utilised for craniofacial analysis and identification. These standards originate from a wide variety of sources, such as orthodontic, maxillofacial, surgical, anatomical, anthropological and forensic literature, and numerous media have been employed to collect data from living and deceased subjects. With the development of clinical imaging and the enhanced technology associated with this field, multiple methods of data collection have become accessible, including Computed Tomography, Cone-Beam Computed Tomography, Magnetic Resonance Imaging, Radiographs, Three-dimensional Scanning, Photogrammetry and Ultrasound, alongside the more traditional in vivo methods, such as palpation and direct measurement, and cadaveric human dissection. Practitioners often struggle to identify the most appropriate standards and research results are frequently inconsistent adding to the confusion. This paper aims to clarify how practitioners can choose optimal standards, which standards are the most reliable and when to apply these standards for craniofacial identification. This paper describes the advantages and disadvantages of each mode of data collection and collates published research to review standards across different populations for each facial feature. This paper does not aim to be a practical instruction paper; since this field encompasses a wide range of 2D and 3D approaches (e.g., clay sculpture, sketch, automated, computer-modelling), the implementation of these standards is left to the individual practitioner.

Materials and Methods for All-Ceramic Dental Restorations Using Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) Technologies-A Brief Review

The materials used in dentistry for the fabrication of all-ceramic restorations have undergone great and rapid developments over the last two decades. Among the most common ceramic materials in dentistry are those based on zirconium and lithium disilicate. Due to the properties of these materials, they are in great demand in the field of dental restoration production. Thus, dental restorations that will use those materials are commonly machined in CAD/CAM systems, which offer the possibility of manufacturing all-ceramic dental restorations in a very short period of time. This article reviews the modern materials in the field of all-ceramic dental restorations, their manufacturing processes, as well as what determines which ceramic materials are used for the production of CAD/CAM blanks and their production technology.

The state of additive manufacturing in dental research - A systematic scoping review of 2012-2022

Background/purpose

Additive manufacturing (AM), also known as 3D printing, has the potential to transform the industry. While there have been advancements in using AM for dental restorations, there is still a need for further research to develop functional biomedical and dental materials. It's crucial to understand the current status of AM technology and research trends to advance dental research in this field. The aim of this study is to reveal the current status of international scientific publications in the field of dental research related to AM technologies.

Materials and methods

In this study, a systematic scoping review was conducted using appropriate keywords within the scope of international scientific publishing databases (PubMed and Web of Science). The review included related clinical and laboratory research, including both human and animal studies, case reports, review articles, and questionnaire studies. A total of 187 research studies were evaluated for quantitative synthesis in this review.

Results

The findings highlighted a rising trend in research numbers over the years (From 2012 to 2022). The most publications were produced in 2020 and 2021, with annual percentage increases of 25.7% and 26.2%, respectively. The majority of AM-related publications in dentistry research originate from Korea. The pioneer dental sub-fields with the ost publications in its category are prosthodontics and implantology, respectively.

Conclusion

The final review result clearly stated an expectation for the future that the research in dentistry would concentrate on AM technologies in order to increase the new product and process development in dental materials, tools, implants and new generation modelling strategy related to AM. The results of this work can be used as indicators of trends related to AM research in dentistry and/or as prospects for future publication expectations in this field.

Automatic registration of dental CT and 3D scanned model using deep split jaw and surface curvature

BACKGROUND AND OBJECTIVES

In the medical field, various image registration applications have been studied. In dentistry, the registration of computed tomography (CT) volume data and 3D optically scanned models is essential for various clinical applications, including orthognathic surgery, implant surgical planning, and augmented reality. Our purpose was to present a fully automatic registration method of dental CT data and 3D scanned models.

METHODS

We use a 2D convolutional neural network to regress a curve splitting the maxilla (i.e., upper jaw) and mandible (i.e., lower jaw) and the points specifying the front and back ends of the crown from the CT data. Using this regressed information, we extract the point cloud and vertices corresponding to the tooth crown from the CT and scanned data, respectively. We introduce a novel metric, called curvature variance of neighbor (CVN), to discriminate between highly fluctuating and smoothly varying regions of the tooth crown. The registration based on CVN enables more accurate fine registration while reducing the effects of metal artifacts. Moreover, the proposed method does not require any preprocessing such as extracting the iso-surface for the tooth crown from the CT data, thereby significantly reducing the computation time.

RESULTS

We evaluated the proposed method with the comparison to several promising registration techniques. Our experimental results using three datasets demonstrated that the proposed method exhibited higher registration accuracy (i.e., 2.85, 1.92, and 7.73 times smaller distance errors for individual datasets) and smaller computation time (i.e., 4.12 times faster registration) than one of the state-of-the-art methods. Moreover, the proposed method worked considerably well for partially scanned data, whereas other methods suffered from the unbalancing of information between the CT and scanned data.

CONCLUSIONS

The proposed method was able to perform fully automatic and highly accurate registration of dental CT data and 3D scanned models, even with severe metal artifacts. In addition, it could achieve fast registration because it did not require any preprocessing for iso-surface reconstruction from the CT data.

An overview of three-dimensional imaging devices in dentistry

OBJECTIVE

To review four types of three-dimensional imaging devices: intraoral scanners, extraoral scanners, cone-beam computed tomography (CBCT), and facial scanners, in terms of their development, technologies, advantages, disadvantages, accuracy, influencing factors, and applications in dentistry.

METHODS

PubMed (National Library of Medicine) and Google Scholar databases were searched. Additionally, the scanner manufacturers' websites were accessed to obtain relevant data. Four authors independently selected the articles, books, and websites. To exclude duplicates and scrutinize the data, they were uploaded to Mendeley Data. In total, 135 articles, two books, and 17 websites were included.

RESULTS

Research and clinical practice have shown that oral and facial scanners and CBCT can be used widely in various areas of dentistry with high accuracy.

CONCLUSION

Although further advancement of these devices is desirable, there is no doubt that digital technology represents the future of dentistry. Furthermore, the combined use of different devices may bring dentistry into a new era. These four devices will play a significant role in clinical utility with high accuracy. The combined use of these devices should be explored further.

CLINICAL SIGNIFICANCE

The four devices will play a significant role in clinical use with high accuracy. The combined use of these devices should be explored further.

High-resolution 3D shape measurement with extended depth of field using fast chromatic focus stacking

Close-range 3D sensors based on the structured light principle have a constrained measuring range due to their depth of field (DOF). Focus stacking is a method to extend the DOF. The additional time to change the focus is a drawback in high-speed measurements. In our research, the method of chromatic focus stacking was applied to a high-speed 3D sensor with 180 fps frame rate. The extended DOF was evaluated by the distance-dependent 3D resolution derived from the 3D-MTF of a tilted edge. The conventional DOF of 14 mm was extended to 21 mm by stacking two foci at 455 and 520 nm wavelength. The 3D sensor allowed shape measurements with extended DOF within 44 ms.

Sinus Lift and Implant Insertion on 3D-Printed Polymeric Maxillary Models: Ex Vivo Training for In Vivo Surgical Procedures

Background and Objectives: The aim of this study is to demonstrate the increased efficiency achieved by dental practitioners when carrying out an ex vivo training process on 3D-printed maxillaries before performing in vivo surgery. Materials and Methods: This developed ex vivo procedure comprises the following phases: (i) scanning the area of interest for surgery; (ii) obtaining a 3D virtual model of this area using Cone Beam Computed Tomography (CBCT); (iii) obtaining a 3D-printed model (based on the virtual one), on which (iv) the dental practitioner simulates/rehearses ex vivo (most of) the surgery protocol; (v) assess with a new CBCT the 3D model after simulation. The technical steps of sinus augmentation and implant insertion could be performed on the corresponding 3D-printed hemi-maxillaries prior to the real in vivo surgery. Two study groups were considered, with forty patients divided as follows: Group 1 comprises twenty patients on which the developed simulation and rehearsal procedure was applied; Group 2 is a control one which comprises twenty patients on which similar surgery was performed without this procedure (considered in order to compare operative times without and with rehearsals). Results: Following the ex vivo training/rehearsal, an optimal surgery protocol was developed for each considered case. The results of the surgery on patients were compared with the results obtained after rehearsals on 3D-printed models. The performed quantitative assessment proved that, using the proposed training procedure, the results of the in vivo surgery are not significantly different (p = 0.089) with regard to the ex vivo simulation for both the mezio-distal position of the implant and the distance from the ridge margin to sinus window. On the contrary, the operative time of Group 1 was reduced significantly (p = 0.001), with an average of 20% with regard to in vivo procedures performed without rehearsals (on the control Group 2). Conclusions: The study demonstrated that the use of 3D-printed models can be beneficial to dental surgeon practitioners, as well as to students who must be trained before performing clinical treatments.

Dental Diagnosis and Treatment Assessments: Between X-rays Radiography and Optical Coherence Tomography

A correct diagnosis in dental medicine is typically provided only after clinical and radiological evaluations. They are also required for treatment assessments. The aim of this study is to establish the boundaries from which a modern, although established, imaging technique, Optical Coherence Tomography (OCT), is more suitable than the common X-ray radiography to assess dental issues and treatments. The most common methods for daily-basis clinical imaging are utilized in this study for extracted teeth (but also for other dental samples and materials), i.e., panoramic, intraoral radiography, and three-dimensional (3D) cone beam computed tomography (CBCT). The advantages of using OCT as an imaging method in dentistry are discussed, with a focus on its superior image resolution. Drawbacks related to its limited penetration depth and Field-of-View (FOV) are pointed out. High-quality radiological investigations are performed, measurements are done, and data collected. The same teeth and samples are also imaged (mostly) with an in-house developed Swept Source (SS)-OCT system, Master-Slave enhanced. Some of the OCT investigations employed two other in-house developed OCT systems, Spectral Domain (SD) and Time Domain (TD). Dedicated toolbars from Romexis software (Planmeca, Helsinki, Finland) are used to perform measurements using both radiography and OCT. Clinical conclusions are drawn from the investigations. Upsides and downsides of the two medical imaging techniques are concluded for each type of considered diagnosis. For treatment assessments, it is concluded that OCT is more appropriate than radiography in all applications, except bone-related investigations and periodontitis that demand data from higher-penetration depths than possible with the current level of OCT technology.

E-quality Control in Dental Metal Additive Manufacturing Inspection Using 3D Scanning and 3D Measurement

3D printed metal crowns can be used for dental restorations. The main quality control challenge of these dental metal is the method of quality inspection. Electronic quality is a process by which the quality of the process and the parts produced can be checked online, thereby improving the process and reducing the time it takes for the entire process. Here, we propose a combination of 3D scanning and 3D measurement for 3D inspection of metal crowns. The data extracted from the 3D printed metal crowns were used as case studies to prove the proposed methodology. The obtained results confirm that the new method has very high classification accuracy compared with the traditional inspection methods, and thus yields excellent results. Moreover, the proposed approach is capable to archive 3D models of the parts and achieve rapid quality control. This paper forms the basis for solving many other similar problems that occur in 3D printing related industries.

Critical Components of Industry 5.0 Towards a Successful Adoption in the Field of Manufacturing

The fifth industrial revolution is known as Industry 5.0 and is being evolved to focus on the personalized demand of customers. This industrial revolution is required to provide better interaction among humans and machines to achieve effective and faster outcomes. It provides a new era of personalization and solves complex problems. Digital technologies provide a new paradigm in manufacturing and eliminate repetitive jobs. It applies human intelligence to understand the requirement of a human operator. The data in manufacturing can be analyzed using machine learning and artificial intelligence (AI). This paper discusses the development of all industrial revolutions and differentiates between Industry 4.0 and Industry 5.0. Further, it identifies the significant elements and capabilities of Industry 5.0 in the manufacturing field. This paper finally identifies 17 critical components of Industry 5.0 and discusses them briefly. Intelligent machines used in this revolution are efficiently used to solve real problems. It provides higher accuracy and speeds up the industrial automation with the help of critical thinking of human resources. Industry 5.0 provides computing power to the industry, which is to facilitate the digital manufacturing systems that are built to communicate with other systems. Thus, with mass personalization, there is customer delight with higher value addition through Industry 5.0.

Challenges of Co-Cr Alloy Additive Manufacturing Methods in Dentistry-The Current State of Knowledge (Systematic Review)

Complex dental components which are individually tailored to the patient can be obtained due to new additive manufacturing technology. This paper reviews the metallic powders used in dental applications, the fabrication process (build orientation, process parameters) and post-processing processes (stress relieving, surface finishing). A review of the literature was performed using PubMed, ScienceDirect, Mendeley and Google Scholar. Over eighty articles were selected based on relevance to this review. This paper attempts to include the latest research from 2010 until 2020, however, older manuscripts (10 articles) were also selected. Over 1200 records were identified through the search; these were screened for title and/or summary. Over eighty articles were selected based on relevance to this review. In order to obtain a product which can be used in clinical applications, the appropriate manufacturing parameters should be selected. A discussion was made on optimal selective laser melting (SLM) parameters in dentistry. In addition, this paper includes a critical review of applied thermal treatment methods for Co-Cr alloys used in dentistry.

Reliability and Accuracy of MRI in Orthopedics: A Survey of Its Use and Perceived Limitations

Over the past decade, the use of magnetic resonance imaging (MRI) as a diagnostic tool has been increasing significantly in various fields of medicine due to its wide array of applications. As a result, its diagnostic efficacy and reliability come into question. Specifically, in the field of orthopedics, there has been little discussion on the problems many physicians face while using MRIs in practice. To gauge the perceived limitations of MRI, we designed a decision analysis to analyze the utility of MRIs and estimate the number of inconclusive MRIs ordered within an orthopedic practice to explore potential alternative avenues of diagnosis. A survey of 100 board-certified practicing orthopedic surgeons given at 2 national conferences was designed to assess the value, reliability, and diagnostic utility of MRIs in preoperative planning in shoulder and knee surgery. Of those surveyed, 93% reported that there was believed to be a problem with the accuracy of an MRI in the setting of a prior surgery and/or if previous hardware was present specifically pertaining to the knee or shoulder. The most common indications of concern regarding knee or shoulder MRI reliability among this sample group were previous patient hardware (19%), a previous surgery (16%), and a chondral defect (11%). In addition, when asked how many MRIs were believed to be inconclusive based on previous surgery/hardware alone in the last 6 months of practice, an average of 19 inconclusive MRIs was reported. This study summarizes some of the concerns of MRI use in the orthopedic community and attempts to add a unique perspective on the attitudes, decision-making, and apparent economic problems that they face as well as uncover specific instances where MRIs were determined to be unreliable and incomplete in aiding the diagnosis and treatment algorithm.

Enablers, Barriers, and Critical Success Factors for Effective Adoption of Color-Jet 3D Printing Technology

Color-jet 3D printing (CJP) technology-based machines are now being developed, and there is a need to identify the successful adoption of this technology for additive manufacturing (AM). Extensive literature review complemented with experts’ advice utilized systematically helped in the identification of 12 critical factors for the effective adoption of color-jet printing technology. A hierarchical structural model is developed using interpretive structural modeling (ISM) and analyzed using Matriced Impacts Croise’s Multiplication Appliquée a UN Classement (MICMAC). Identified software and the machine cost are primary drivers for this color-jet 3D printing machines (technology). The value of this technology is to provide the product at a lower cost and give useful applications in the area of medical, engineering and concept building. There is a need for developing better quality core material and post-processing material, further supported by enabling machine hardware and software. Accuracy and color texture of the part produced are essential to provide a technological advantage over existing technologies. Post-processing assists in a big way in imparting necessary properties to the part produced. Presently, the infiltrate/post-processing materials are limited, and for large-scale acceptability, one needs extensive multidisciplinary research and development. This research provides a structural model toward the adoption of color-jet 3D printing technology, which can also help users in evaluating this technology in broader AM framework.

The Popular Culture of 3D Printing

As 3D printing technology achieves mainstream adoption, people are forming new relationships with products as they shift from passive consumers to “prosumers” capable of both producing and consuming objects on demand. This is fueled by expanding online 3D printing communities, with new data within this chapter suggesting that prosumers are challenging existing understandings of popular culture as they bypass traditional mass manufacturing. With 3D digital files rapidly distributed through online platforms, this chapter argues that a new trend for “viral objects” is emerging, alongside the “3D selfie,” as digital bits spread via the internet are given physical form through 3D printing in ever increasing quantities. Analysis of these trends will provide academics, educators, and prosumers with a new perspective of 3D printing's socio-cultural impact, and further research directions are suggested to build a broader discourse around the opportunities and challenges of a cyberphysical future.

An insight into biomimetic 4D printing

4D printed objects are indexed under additive manufacturing (AM) objects. The 4D printed materials are stimulus-responsive and have shape-changing features. However, the manufacturing of such objects is still a challenging task. For this, the designing space has to be explored in the initial stages, which is lagging so far. This paper encompasses two recent approaches to explore the conceptual design of 4D printed objects in detail: (a) an application-based modeling and simulation approach for phytomimetic structures and (b) a voxel-based modeling and simulation approach. The voxel-based modeling and simulation approach has the enhanced features for the rapid testing (prior to moving into design procedures) of the given distribution of such 4D printed smart materials (SMs) while checking for behaviors, particularly when these intelligent materials are exposed to a stimulus. The voxel-based modeling and simulation approach is further modified using bi-exponential expressions to encode the time-dependent behavior of the bio-inspired 4D printed materials. The shape-changing materials are inspired from biological objects, such as flowers, which are temperature-sensitive or touch-sensitive, and can be 4D printed in such a way that they are encrypted with a decentralized, anisotropic enlargement feature under a restrained alignment of cellulose fibers as in the case of composite hydrogels. Such plant-inspired architectures can change shapes when immersed in water. This paper also outlines a review of the 4D printing of (a) smart photocurable and biocompatible scaffolds with renewable plant oils, which can be a better alternative to traditional polyethylene glycol diacrylate (PEGDA) to support human bone marrow mesenchymal stem cells (hMSCs), and (b) a biomimetic dual shape-changing tube having applications in biomedical engineering as a bioimplant. The future applications would be based on these smart and intelligent materials; thus, it is important to modify the existing voxel-based modeling and simulation approach and discuss efficient printing methods to fabricate such bio-inspired materials.

4D printed objects are indexed under additive manufacturing (AM) objects.