3D printing and 3D scanning for the dental industry
What is digital dentistry?
For many years, dental and orthodontic procedures followed a similar pattern: patients would bite down on chunks of a gooey material, which would be used to make a plaster model of the patient’s teeth. This model would be sent to a lab where, with manual design and casting, it would be turned into a dental model, restoration, or appliance.
That workflow is today becoming shorter and more accurate. Modern technologies like 3D scanning, 3D modeling, and 3D printing have opened up new possibilities in dentistry, cutting out surplus steps in the process and improving the patient experience. The term “digital dentistry” encompasses these technologies and their workflows.
The digital dentistry workflow
Before we take a look at hardware and software, let’s see what the overall digital dentistry workflow includes.
Digital dentistry can be thought of as comprising three general areas:
- imaging, in which visual data is obtained of a patient’s mouth;
- modeling, in which dental models, restorations, and appliances are digitally designed on computers using specialist software;
- and fabrication, in which the dental products are built using digital manufacturing hardware.
In certain branches of dentistry like oral pathology and oral medicine, the digital dentistry workflow may go no further than the imaging stage; in such a scenario, scan data is obtained to allow a dentist to make a diagnosis and prescribe a course of treatment.
But this guide focuses on disciplines like orthodontics, oral implantology, and prosthodontics, in which the tools of digital dentistry are used to design and fabricate models, restorations, and appliances to tackle cosmetic or medical issues.
The following sections dive deeper into the three main areas of digital dentistry (imaging, modeling, and fabrication) and their technologies.
Imaging: Dental impressions and 3D scanning
Although digital dentistry is reducing the industry’s dependence on traditional impressions, this technique, used to obtain an imprint of a patient’s teeth, is still important in many digital dentistry workflows.
To make a dental impression, a dentist fills an impression tray with a semi-solid material such as an alginate; the patient bites down on this material, leaving an imprint upon it. The material solidifies after a few minutes, and the dentist can then use the dental impression for many different applications.
3D scanners are pieces of imaging hardware used to obtain highly detailed visual information about a patient’s teeth.
The scanning process can take place inside a patient’s mouth (intraoral 3D scanning) or in a laboratory, where 3D scans can be made of pre-obtained dental impressions (desktop 3D scanning) or models. Dental 3D scanners typically use a combination of structured light or laser projection and high-resolution cameras.
Cone-beam computed tomography (CBCT), which uses X-rays instead of light and cameras, is another common dental imaging technology.
3D scanners are used to obtain a digital 3D model of a patient’s teeth, and this 3D model or “digital twin” can be useful for diagnosis, comparison, or archiving.
3D scans can also be edited and manipulated using Computer-Aided Design (CAD) software in order to create a physical dental model, restoration, or appliance.
The nature of the modeling process depends on what is being made. With prosthodontic devices like aligners and retainers, the CAD software can be used to plan desired tooth movement over time; with replacement crowns, a scan of a broken tooth may need to be digitally “rebuilt” so it is ready for fabrication.
The digital design needs to be converted into instructions that are readable by the relevant piece of manufacturing equipment. Computer-Aided Manufacturing (CAM) software performs this task, similarly to slicing software programs (“slicers”) that transform STL files into Gcode for FFF 3D printers.
Digital dentistry involves several fabrication technologies. In terms of new developments and opportunities, the most important of these is 3D printing, but there are several digital dentistry fabrication methods that can be used alone or in conjunction with others.
CNC milling and grinding
Dentists have used mills and grinding machines for decades, but digital dentistry has provided opportunities for the use of Computer Numerical Control (CNC). Subtractive technologies like milling and grinding remove (or sculpt) sections from a block of material, producing end products such as crowns, bridges, or abutments.
In digital dentistry, 3D printers can be used to print end-use models and appliances; they can also be used to make patterns which can be turned into the end product via a subsequent process like thermoforming or casting. The direct printing of end-use parts is becoming more and more widespread.
Like milling and grinding machines, thermoforming machines predate digital dentistry, but they can be used in conjunction with new fabrication techniques like 3D printing. To make modern clear aligners, for example, a model is 3D printed, then a sheet of plastic is thermoformed around it.
However, thermoformed aligners are thicker and sometimes less resistant than directly 3D printed aligners (C. Maspero and G. M. Tartaglia, Nov. 2020).
The process of 3D printing can be combined with the much older process of investment casting to make items like crowns and bridges. Patterns must be 3D printed in a castable resin, which is then used to make a mold. The 3D printed pattern can then be burnt out of the mold, leaving a cavity that can later be filled with a casting material.
Dental 3D scanners
3D scanners are pieces of hardware that capture 3D shapes using cameras and projected light or lasers. In dentistry, 3D scanners can be used in a clinical chairside setting or in a laboratory.
Scanners project structured light or laser beams (parallel laser lines or crosses) onto the scan target, and the light is then captured by cameras. The deformations in the light indicate the 3D shape of the scan target.
Types of dental 3D scanners
- Intraoral 3D scanners: Intraoral dental scanners are handheld devices that 3D scan directly inside a patient’s mouth.
- Desktop 3D scanners: Desktop dental scanners are stationary devices used for accurately scanning items like impressions and models.
Many leading manufacturers of dental 3D scanners, including 3Shape, Dental Wings, Shining 3D, and Medit, offer both intraoral and desktop scanners.
Dental 3D printers
3D printers are additive manufacturing (AM) machines that fabricate parts in a layer-by-layer manner using extruded material, UV-cured resin, fused powder particles, or other means. Dental 3D printers are used to fabricate dental models, implants, restorations, appliances, casting patterns, and other items.
Types of dental 3D printers
- Dental resin 3D printers: resin 3D printers use vat photopolymerization technologies like Stereolithography (SLA) and Digital Light Processing (DLP). They are accurate and can produce Class I biocompatible objects like custom impression trays and Class II objects like crowns. Leading brands include Formlabs, EnvisionTEC, and 3D Systems.
- Dental photopolymer jetting 3D printers: Dental photopolymer jetting 3D printers such as Stratasys’ PolyJet machines are used to 3D print items like detailed models and Class I objects like surgical guides in rigid or flexible materials. Printers like the Stratasys Objet260 are also capable of multi-color, multi-material printing.
- Dental metal 3D printers: Dental metal 3D printers use technologies like Direct Metal Laser Sintering (DMLS) and Selective Laser Melting (SLM) and can be used to 3D print metal guides and instruments as well as Class II objects such as implants, crowns, and bridges. Leading brands include 3D Systems and EOS.
- Dental ceramic 3D printers: Dental ceramic 3D printers like the Lithoz CeraFab S65 can print Class II compatible ceramic objects like crowns and veneers in materials like zirconia. (Some resin 3D printers can also print ceramic-mix resins like Formlabs’ silica-filled Ceramic Resin.)
- Rigid resins: Rigid resins are used in photopolymerization printers and can make items like models, impression trays, and surgical guides. Examples include 3D Systems’ Accura 55 material and EnvisionTEC’s E-AquaModel material.
- Flexible resins: Flexible resins are used in photopolymerization printers and can make soft items like gingiva masks and custom night guards. Examples include EnvisionTEC’s KeySplint Soft material and Formlabs’ Soft Tissue Resin.
- Castable resins: Castable resins are used in photopolymerization printers and contain wax; they can be burnt out during the investment casting process to make molds.
- Metals: Metals like cobalt alloys are used in powder bed fusion printers for the fabrication of restorations like crowns and bridges.
- Ceramics: Ceramic materials like zirconia are used in ceramic printers to make temporary and permanent restorations.
Dental software is required for each step in the digital dentistry workflow: imaging, modeling, and fabrication. Individual applications may be used for these separate tasks, or an end-to-end or all-in-one dentistry suite may be used to cover them all.
Software suites are generally not included with dental hardware and can even end up being more expensive than the 3D scanning or 3D printing equipment itself. Leading dental software programs cost at least several thousand dollars, and can even go beyond $10,000.
Although the tendency is to streamline and standardize digital dentistry workflows and equipment, not all 3D scanners and 3D printers are compatible with all dental software solutions.
Types of dental-specific software
- Scanning software: It is used to control 3D scanning hardware. The software creates a point cloud and turns it into a mesh that can be read by CAD/CAM software. Features include workflow management, parameter selection, and target identification.
- CAD: Dental CAD software is used to design dental restorations like crowns, bridges, and veneers, as well as retainers and other items. Meshes are exported from the scanning software and into the CAD environment. Unlike generic CAD software, dental CAD includes tools for the fast generation of specific dental restorations and appliances.
- CAM / nesting / slicing: Different software types are used to control fabrication hardware. Slicing software is used to prepare a 3D print, while nesting software calculates how to fabricate multiple parts on a single printing/milling job. CAD/CAM solutions are often packaged together, CEREC from Dentsply Sirona being one example.
- All-in-one digital dentistry suites: Some software developers offer software suites that cover every stage of the digital dentistry workflow. Exocad, for example, offers solutions for 3D scanning, CAD, and 3D printing.
Advantages of digital dentistry over traditional methods
Although digital dentistry hardware and software can have high up-front costs, switching to digital manufacturing can provide a fast return on investment. For instance, several dental appliances can be 3D printed at the same time on a 3D printer’s build platform, and workflows can be significantly abridged, shortening labor hours and cutting material expenses.
Improved patient experience
Intra-oral 3D scanning is a non-invasive imaging technology which allows dental practitioners to easily obtain a 3D model of their patient’s denture without the use of traditional impressions, which many patients find uncomfortable and which can leave an unpleasant taste in the mouth. Fast turnarounds and an improved end product also benefit the patient.
Moving to digital dentistry using 3D scanning and 3D printing greatly reduces the amount of manual work and labor-intensive tasks in dental manufacturing processes. And cutting out steps in the workflow — the need to make a mold from an impression, for example — reduces the likelihood of errors along the way.
High quality and improved fit
High-end dental 3D printers produce high-quality parts, and accurate 3D scanning and printing ensures a proper fit for the patient. Improvements to printing and post-processing technologies will continue to raise the quality of printed dental models, restorations, and appliances in the future.
When it can take two to three weeks to produce a dental crown with conventional methods, using 3D scanning and 3D printing can bring this number down to a matter of days or less. This has obvious financial benefits for dental practices and laboratories, and medical or cosmetic benefits to patients.
Digital dentistry encompasses different processes, but the integration between, for example, 3D scanning software and CAD software, makes it incredibly easy to move from one stage of the workflow to the next. In some circumstances, imaging, modeling, and fabrication may all be handled on a single computer.
Dentists using traditional methods may still get good results without having to touch a computer, but all signs point to a digital dentistry future. Failing to get ahead of the curve could have negative consequences for labs and clinics down the line.
2021 market outlook & future possibilities
Digital dentistry looks set to continue its growth over the next decade. According to 3dpbm Research, the dental 3D printing market could be worth $7.5 billion by the end of 2021 and $20.6 billion by 2025. Its growth will be driven by increasing demand for “cosmetic dentistry, growing dental tourism, increasing popularity of franchise dentistry, and technological advances in digital dentistry.”
All signs point to digitally fabricated clear aligners becoming even more popular, and they may at some point be predominantly 3D printed directly rather than thermoformed around a 3D printed model. Michigan-based 3D printer manufacturer EnvisionTEC developed a 3D printing resin for the direct printing of clear aligners back in 2018.
A December 2020 report from SmarTech Analysis highlights several key future trends in dental 3D printing, including:
- Ceramic restoration printing
- Permanent printable dental composites
- Printing of true zirconia restorations
Actually, Austrian company Lithoz is already making strides in the printing of zirconia restorations. According to the company, printed veneers made of zirconia “can now have wall thicknesses that were previously unachievable.”
Future possibilities in dental 3D scanning and dental software include AI tools that can diagnose patients by interpreting scan data. According to researchers from the University Medical Centre of Groningen in the Netherlands, “new imaging technologies will make it possible to subjectively grade caries, the periodontium, and soft tissue problems,” effectively enabling computers to analyze patients autonomously. In such a scenario, dentists would only be required if scan results were inconclusive.
Digital dentistry tools like 3D scanners and 3D printers have justified their cost for many dental labs and practices. Formlabs suggests that a lab printing x5 orthodontic models per day at a labor cost of $20/h would break even on a Formlabs resin 3D printer after just 7 weeks.
Increasingly, yes. Although 3D printers are often used indirectly to make molds and castings, the direct printing of restorations is becoming more feasible.
Regulators like the FDA have developed tests for clearing the use of 3D printed restorations.
Integrating disparate dentistry solutions from different providers is often possible since 3D scanners export in common file formats and fabrication tools like 3D printers accept common file formats. However, there can sometimes be incompatibility between different CAD and CAM software libraries.
In any case, software compatibility is something to look out for before making any purchases.