Introduction to Digital Dentistry

Chapter 1
Introduction to Digital Dentistry

Renan L.B. da Silva, Jun Ho Kim, Roberto A. Markarian, Rui Falacho, Djalma N. Cortes, Alan J.M. Costa, and Arthur R.G. Cortes

1.1 Definitions

Digital dentistry is the term used to describe the different modalities of dental treatment workflow that are mostly performed with the use of digital technologies. Several digital methods have been incorporated to dental practice to replace conventional methods and techniques in order to enhance treatment planning and predictability of execution. Nowadays, digital dentistry is considered a whole field of study within dentistry. As with any other field of study, digital dentistry involves a learning curve to be mastered and used in the clinical routine. Ultimately, the dental professional is responsible for using existing digital tools appropriately for patient treatment. In other words, the basic theories of dentistry are still the same and should be very well known by the professional, who will be able to use these new digital tools to enhance predictability in executing the treatment plan.

In order to become familiar with digital dentistry and take advantage of its benefits, it is required to learn a series of important concepts and abbreviations. The most important of these are discussed below.

1.1.1 Three‐Dimensional Imaging

Conventional two‐dimensional (2D) imaging modalities usually have several limitations such as image distortion, magnification, superimposition of anatomical structures, and lack of three‐dimensional (3D) information for diagnosis and planning. In this context, 3D imaging modalities such as cone beam computed tomography (CBCT), intraoral and facial scanning systems provide 3D digital images for dentistry [13]. CBCT imaging allows for visualization and assessment of bone structures with high diagnostic accuracy and precision. For CBCT images, the professional needs to understand image acquisition parameters, since the quality of the image affects the quality of the work in digital dentistry. There are several CBCT acquisition parameters, such as field of view size (FOV), peak kilovoltage (kVp), milliamperage (mA), and voxel size. Each of these parameters has an influence on CBCT quality [25].

Intraoral and facial scanning can capture 3D patient images that can be used for digital treatment planning systems (Figure 1.1). The software will then develop a digital representation of the 3D object surfaces available, which will be automatically converted into 3D images composed by wireframe models.

Any 3D images can be rendered and edited in the 3D space, before being converted and saved in a specific file format [5]. As discussed in the next chapter, three file formats are commonly used in digital dentistry: OBJ, STL, and PLY. These files are based on the geometric reconstruction of objects by vectors, triangles or polygons, considering their positioning in a 3D space. After all data is ready, it is possible to store the shape of a model and other details such as color or texture.

Photo depicts three-dimensional objects imported in different coordinates of the three-dimensional space.

Figure 1.1 Three‐dimensional objects imported in different coordinates of the 3D space (screen capture of MeshMixer software, Autodesk). Note that the fixed bridge is closer to the screen than the molar crown. The dynamic grid is used to orientate the spatial disposition of the 3D objects.

Three‐dimensional images can be manipulated in various ways, depending on the characteristics of the software. For example, with DICOM and STL files, using the CAD software one can plan and perform digital surgery of dental implants and wax‐up of future prostheses. After digital planning, the implant surgery guide, temporary crowns, and definitive crowns can be printed with additive manufacturing devices or milled by subtractive manufacturing devices [5, 6].

1.1.2 Coordinates and Planes

All 3D images are created or rendered in a virtual space of coordinates and planes. Any objects that are digitally designed within the 3D coordinates can be fully edited in the virtual space, before being manufactured. The coordinate system is a method of assigning numbers to points. In three dimensions, three numbers are required to specify a point. Plain 2D images have numbers related to only two coordinates (x and y). The coordinate that represents the third dimension is usually an axis called z. The z‐axis is perpendicular to both the x‐axis and the y‐axis (Figure 1.2).

The coordinates and the respective planes provide references for the location, size, and volume of the 3D images. All 3D objects have their coordinates fixed in a virtual plane of the imaging software. It is important to make sure that multiple 3D objects to be manipulated or aligned are positioned in the same spatial coordinates, which can be used as spatial references. Therefore, 3D files from different imaging methods should be in the same 3D coordinates in order to be superimposed or combined with the aim of creating a virtual patient, as explained further in this chapter.

Photo depicts a three-dimensional object is positioned in the three-dimensional space of a software (Ultimaker Cura) to be three-dimensional printed.

Figure 1.2 A 3D object (reconstructed model of a maxillary CBCT scan) is positioned in the 3D space of a software (Ultimaker Cura) to be 3D printed. Note the three axes depicted by the software in different colors (x‐axis in red, y‐axis in green, z‐axis in blue).

1.1.3 Computer‐Aided Design and Computer‐Aided Manufacturing (CAD‐CAM)

The term computer‐aided/assisted design is usually abbreviated as CAD. The methods used for image acquisition (CBCT, scanning imaging, photographs) and manipulation (software programs) can be included in CAD. On the other hand, computer‐aided/assisted manufacturing (CAM) includes processes such as 3D printers (additive manufacturing) and milling devices (subtractive manufacturing). CAD‐CAM technologies are currently used in biomedical engineering, clinical medicine, customized medical implants, tissue engineering, dentistry, artificial joint manufacture, and robotic surgery. Furthermore, the use of CAD‐CAM technologies has been increasing in various fields of study of medicine and dentistry [5, 6]. Among the main devices that can be digitally designed and manufactured are different types of dental restorations and prostheses, surgical guides, occlusal splints, dental casts, and orthodontic aligners [5, 7]. Details of the main clinical applications of CAD‐CAM in dentistry are further addressed in the next chapters.

1.1.4 Mesh

The term mesh is used to describe the surface of a 3D object composed of triangular or polygon faces. A mesh object does not have any actual curvature. Instead, the appearance of curvatures in a 3D image composed of meshes is obtained by increasing the number of surfaces. The most common file format of these 3D images is the STL file [5], which will be discussed in detail in the next chapter.

1.1.5 Image‐Guided Treatment

Since 3D patient scans are taken prior to dental treatment, CAD‐CAM technology can be used for the fabrication of surgical guides, preparation guides, and maxillofacial surgical templates. Most of these applications require 3D hard and soft tissue images generated by CBCT and optical scanning image modalities, respectively. Based on such images, CAD‐CAM guides can be designed and manufactured to orientate directions of drilling procedures and incisions [5].

1.1.6 Image Superimposition/Alignment

Distinct 3D image files like DICOM and STL can be overlaid or aligned using CAD software. In the field of digital dentistry, aligning DICOM and STL is useful to plan implant placement. Details of image alignment will be addressed in the next chapter.

1.1.7 Resolution

In 2D images, the resolution depends on the number of pixels. A pixel is the smallest unit of a digital image that can be displayed and represented on a digital display device, also known as a picture element (pix = picture, el = element). A pixel is represented by a dot or square on a computer display screen. Pixels are the basic building blocks of a digital image or display and are created using geometric coordinates. Depending on the graphics card and display monitor, the quantity, color combination, and size of pixels vary and are measured in terms of the display resolution. A full high‐definition (full HD) image is 1920 pixels in width and 1080 pixels in height, totaling 2.07 megapixels. Ultra HD (also known as 4 K) resolution has 3840 × 2160 pixels, totaling 8.3 megapixels.

The 3D version of a pixel is called a voxel. In general, the smaller the voxel size is, the better quality a 3D reconstructed model will have.

The quality of radiographic images depends on contrast resolution and spatial resolution. Contrast resolution is proportional to the size of the contrast scale available to produce the image. As a result, the higher the contrast resolution of an image, the easier it will be to distinguish between multiple densities. In digital imaging, contrast resolution depends on the bit‐depth of the imaging method, following a logarithmic scale. Therefore, a panoramic radiograph produced with an 8‐bit system can show 28 = 256 different gray‐scale levels distributed from black to white. A CBCT device with a 12‐bit system will offer 212 = 4096 gray‐scale values. Spatial resolution is the ability of an imaging method to identify the actual limits and differentiate two adjacent structures [24].

Resolutions in 3D CAD files basically depends on the size and densities of the meshes. The quality of the respective manufactured device, however, is also dependent on factors related to CAM (e.g., resolution of 3D printers or milling devices). For 3D printers, there will be factors related to the resolution such as the number of layers and layer thicknesses. For milling machines, the resolution will be dependent on the number of axes and size of burs (see Chapter 3).

1.2 History of Digital Dentistry

Science and technology are the foundations of human development. From the rudimentary creation and improvement of stone tools, accompanied by the breakthrough in learning to control fire and the Neolithic revolution, which multiplied the sustenance availability, to the significant invention of the wheel which allowed humans to travel and produce machinery, or the overcoming of physical barriers with advancements in communications, technology is what sets humanity apart.

Alongside technology, a lexicon development has always been necessary to provide a common understanding of innovations in the meaning and usage of new or existing words. The technological lexicon expansion will often plainly exhibit a novel sense in use but also a rationalization as to why a fresh sense has surfaced. This derives from the need to name new inventions, and when these ascend to a well‐known state, so does the correlated terminology. A widespread example of this lexicon expansion is the “digital” concept which, in the last century, underwent a huge increase in usage and meaning as an unswerving consequence of modern computing.

However, contrary to what is customary in technology, the term “digital” is by no means a new word. With its etymology in the Latin word digitus, meaning finger or toe, “digital” has come a long way since. In the fifteenth century, the word was used to identify Arabic numbers from 1 to 9 and 0 as digits. It was not until the twentieth century that the term became widespread and gained significance. In the 1930s and 1940s, the existing analogue computing devices which computed data with the normal decimal system were replaced by new machines which functioned with data represented as sequences of discrete digits.

In the late 1970s, electronics using the digital concept were no longer limited to research institutions and companies. As their cost dropped, the general public started to have access and myriad information sources and equipment were converted to the digital era. From a simple CD to a more complex digital sensor camera, radiovisiography or 3D scanner, the world was changed forever.

The construct of “digital” did not stop with machine development but acquired a broader meaning. It has evolved to encompass everything linked to digital or computer technology, as well as to describe any computer‐mediated equivalent of an object or entity that exists in the palpable world. Daily uses of this concept are digital shopping carts and digital books, among others. Not only ordinary objects but also professions, expertise fields, and whole organizations acquire the digital connotation when they embrace technology (either hardware or software) for their activities. Examples of this are the many references to digital dentistry or the thriving European Academy of Digital Dentistry that quickly became one of the most respected and widespread scientific societies in the dental field.

Although the twentieth century was overflowing with the word “digital” as the most significant technological innovation in human history, it is predictable that the twenty‐first century renders the word “digital,” but not the concept, obsolete. As digital becomes the norm, the need to identify it as such becomes archaic. Fields like digital dentistry will overrun the previous model as all dentistry becomes digital, thus eliminating the need for an alias. Similar to the previously named “digital computers,” so digital wax‐ups, digital photography, and many more entities will lose the superfluous prefix.

Having discussed the past, present, and future general notions of digital, it is imperative to clarify the current concept of digital dentistry, as it may not comply with the ingrained notion promoted and labeled by the industry. Although more widely marketed in oral rehabilitation and surgery fields, digital dentistry has a vast predominance in endodontics, cariology, periodontics, orthodontics, and occlusion, among others. Nowadays, it is clear that digital dentistry encompasses all areas and not only the well‐marketed misconception of “digital” as a synonym of CAD‐CAM dentistry, a common buzzword in oral healthcare. CAD‐CAM technology presents a vast sea of innovation opportunities and is undoubtedly one of the drivers of development in modern dentistry. Nonetheless, according to the concept regulated by the European Academy of Digital Dentistry, “Digital dentistry encompasses any and all scientific, clinical or laboratory techniques and/or procedures with the purpose of examining, diagnosing, treating, assisting directly or indirectly in the treatment, production of medical devices or any other techniques used by dentists and dental technicians to better pursue the goal of improving patient treatment, comfort and outcome, as well as the healthcare professional’s work environment.”

Taking the aforementioned concept, it is perceivable that dentistry areas such as endodontics present an even higher digitalization than other more well‐known digital fields, as endodontists dwell in a fully digitalized workspace where all clinical procedures are performed with the aid of technology – diagnostics with 2D or 3D radiology, microscopes and cameras, apex finders, ultrasonic technology for accessing root canals, static and dynamic endodontic guides, instrumentation with highly advanced digital motors, irrigation activation techniques, and warm obturation methods.

The mandatory multidisciplinary approach in digital dentistry renders the task of defining a clear historical timeline impossible, as innumerable events, developments and clinical or laboratory fields are involved and intertwined in the modern concept.

However, focusing on oral rehabilitation and the developments in computer‐aided design and manufacturing, the first CAD‐CAM systems in dentistry date to 1971 when Dr François Duret introduced them in his DDS graduation thesis “Optical Impression,” but the technology had been used since the 1960s in the automobile and aircraft industries.

In 1984, Dr Duret patented a CAD‐CAM device, which was presented at the Chicago Dental Society Midwinter Meeting of 1989, where a dental crown was fabricated in a record time of 4 hours. In parallel, Dr Werner Mormann worked on the development of a digital scanning system to be used by the general dentist, which was branded CEREC 1 and launched in 1985. This innovative system was composed of a three‐dimensional digital scanner and milling machine which, when combined, would allow dentists to produce chairside ceramic inlays and onlays in single appointments.

Since then, the technology has greatly improved and dentists and dental technicians experience a time when CAD‐CAM can produce results that resemble pure magic, which is what happens when technology is advanced enough. The next two chapters of this book will cover CAD‐CAM technology and available procedures in depth.

The advent of 3D printing is revolutionizing several dentistry fields, improving the quality and precision of surgical techniques, and gaining a massive preponderance in restorative dentistry. The term 3D printing defines a manufacturing process in which additive techniques are used to build objects one layer at a time, in contrast to milling techniques that require a material block to be ground to the final desired shape.

Engineer Charles Hull introduced the first 3D printing technology in 1986 with his patented stereolithography (SLA) system and 4 years later, Scott Crump patented the fused deposition modeling (FDM) technique. Widely used in a multitude of manufacturing fields for the last 30 years, 3D printing with newly developed materials is on the verge of radically changing general medicine and dentistry. From the production of surgical guides, study casts, mock‐ups, temporary indirect restorations, occlusal splints, and orthodontic aligners to the more recent production of long‐term resin restorations, complete dentures and even titanium dental implants, this additive technology is thought to be the future of CAM, with some much anticipated innovations in materials and techniques that will soon allow ceramic restorations to be printed with higher customization possibilities and lower raw material waste.

With the advent of diagnosis, patient and case documentation, treatment planning, novel treatment techniques and more recently throughout the workflow in oral rehabilitation, digital dentistry is a reality with a promising future. However, much more is yet to come and other fields such as artificial intelligence (AI) will play a major and currently unimaginable role in overcoming all known boundaries. Already considered a rising field, AI technology in dentistry has been the focus of serious research. Software with deep learning capabilities is already helping to improve orthodontic treatment outcomes, caries diagnosis, diagnosis and prediction of periodontal diseases, risk assessment of oral cancer, treatment plan suggestions, patient data analysis, and smile design, among others.

Companies like Pearl, Smilecloud, and LM Instruments, among many others, lead the development of new tools and software capable of autonomously predicting pathology, suggesting treatment plans or providing solutions to improve clinical management and maximize cost‐effective approaches, as well as patient safety.

Within its many limitations and shortcomings, digital dentistry is an unavoidable new reality. However, it should not be considered as a means of solving all problems and dentist/dental technician errors, but rather as a tool to maximize and improve processes already performed adequately.

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Nov 13, 2022 | Posted by in General Dentistry | Comments Off on Introduction to Digital Dentistry
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