3D Printing in Dentistry: Everything You Need to Know
3D printing plays a crucial role in dentistry, just like in many other industries. It is useful in producing customized patient oral structures, like dental implants, that precisely match the patient’s unique anatomy. Dental professionals can quickly produce prototypes and even fully functioning dental products that meet the specific requirements of the patients. Unlike traditional methods like dental impressions that involve creating molds of a patient's teeth using materials like alginate or silicone, it can be uncomfortable for patients and may not always provide the level of detail required for complex cases. Also, it can take more time to customize, and hence 3D printing is a great alternative. Dental 3D printing involves the layer-by-layer construction of dental objects, ranging from crowns and bridges to surgical guides and anatomical models. The process typically follows these key steps.
Step 1: 3D Scanning and Creation of a Digital Model
Unlike in other 3D printing methods, where the process begins with creating a 3D model using CAD software, in dentistry, the digital 3D model is created using a 3D scanner. You will need to use a handheld 3D scanner, like an intraoral scanner, to capture the detailed 3D images of the patient’s teeth and surrounding oral structures. An intraoral scanner uses advanced optical or laser technology to capture high-resolution images of the teeth and the surrounding tissues. As you move the scanner around, the scanner instantly displays the images in real-time as the captured images are instantly displayed on a connected monitor, making it easier to visualize the digital impressions as they are being taken. Most are also comfortable as the patients don’t need to endure the discomfort of having trays filled with impression material in their mouths, which can be messy and painful sometimes.
As you navigate the scanner along the teeth, detailed images of the lower and upper arches will be taken if you need all of them. The patients can also be instructed to bite down on a specific area while the scanner captures the necessary data. This ensures that a bite registration is also taken. Each generated surface in the scan represents a 3D mesh that contains thousands of triangles, and the images of the object captured are mapped on the meshes.
Once you finish generating the scans, you need to import them into CAD software in order to convert them to a printable format. Sometimes, you will also need to make further adjustments and clean it up before 3D printing. Different 3D scanners support different file formats; below are the main ones.
File Formats for 3D Scanning
One of the file formats for 3D scanning is the polygon files. These are mesh files that can be in the form of STL, PLY, or OBJ, and they are the most common file formats that most 3D scanners output. STL is one of the earliest and most widely used file formats for 3D printing and computer-aided design. It represents a 3D surface geometry using a series of connected triangles. STL files can be in either ASCII or binary format. Binary STL files are more compact and are the preferred format for 3D printing. PLY (Polygon File Format) is a flexible file format that can store 3D data in ASCII and binary formats. It supports a variety of data properties, including color, transparency, and texture coordinates. PLY files are commonly used in applications where additional attributes beyond geometry, such as color information, are needed. OBJ (Wavefront .obj file) can contain both geometry and material information, making them suitable for more complex 3D scenes. These file formats serve as a means to represent the scanned geometry of an object. Also, most of the polygon designs are “watertight,” which means that the model represents a solid object without any openings.
Some 3D scanners support IGES and STEP, which can be used in most CAD software. IGES files store not only the 3D geometry but also additional information such as colors, layers, and annotations. This makes it a comprehensive format for transferring 3D models. 3D scanners that output STEP files ensure compatibility with a broad range of CAD software, as nearly all major CAD systems support STEP. STEP files can include parametric information about the geometry, making them particularly useful for conveying detailed design and engineering data.
After scanning, the output from the 3D scanner is often saved in one of these formats, and subsequent steps may involve using CAD software to modify or optimize the 3D model before 3D printing.
Step 2: Creating 3D Models from 3D Scans
Once you have prepared digital scans, you will need to use a Computer-Aided Design (CAD) software to make them 3D printable and modify them further. Many programs are available, but the most used are Exocad and SelfCAD, and we will look at each of them.
Using Exocad to Prepare Scans for 3D Printing
Exocad is one of the most powerful and popular software used in dentistry. You can use it to work on various dental restorations like crowns, bridges, and dental appliances. DentalCAD, one of Exocads’ software works with most 3D scanners and 3D printers, and users can access various materials and libraries for different manufacturers. DentalCAD also has a guided workflow that guides you through every step of the dental restoration process. It’s also easier to combine open data from different sources virtually based on your needs. For example, you can combine intraoral and model scans, 3D face fans, jaw motion data, and user photos.
In addition to creating fully functional designs like crowns, it has an extensive library that you can use to add or remove attachment shapes on your designs. Working on inlay and onlay restorations is easier, too, and you can also scan, edit, or create waxups from scratch. The software also allows you to add various add-ons and modules to DentaCAD to let you tailor it based on your needs. A good example of the module is the implant module that allows you to create abutments and screw-retained designs. Model Creator plugin allows you to create physical designs from digital impression scans. If you want to create realistic dental restoration renders, you can use the Trusmile Module. If you’re working on full dentures, you can get the FullDenture module. It has a workflow that you can use to create full dentures in a single or in both jaws.
When you are done with 3D modeling and want to 3D print your dentures, you will need to use the Exoprint software. It supports many 3D printers, and you can integrate it into your various 3D printing software using the XML-based interface.
Using SelfCAD to Prepare Scans for Dentistry
SelfCAD is another great tool useful for dentists and professionals working on dentures. SelfCAD is an easy-to-use 3D modeling software that you can import your 3D scans and modify them based on your needs. In addition to coming with tools for creating 3D models from scratch, the software also has tools for fixing meshes, like the Magic Fix tool, ensuring that your designs are ready for 3D printing. There is also an in-built online slicer useful for slicing your designs and generating the G-code, the file format that 3D printers can read and interpret. Unlike Exocat, which requires you to have add-ons and modules for almost every task, all the important tools for working on your dentures are easily accessible on SelfCAD interface at the click of a button. You can follow the steps below to modify your 3D scans, fix meshes, and even close any gaps if there are any.
Importing and Modifying 3D Scans in SelfCAD
To import the file, go to File > Import.
You can then go to where your files are stored and import them into the software. Sometimes, your designs can have gaps, especially between teeth, that need filling. The gap can vary in size, ranging from small, barely noticeable spaces to larger gaps that can affect the smile's appearance. Orthodontic treatments, dental restorations, and cosmetic dentistry procedures are among the options available for addressing teeth gaps, depending on the cause and severity of the gap. To avoid all those processes, you can fix them easily in SelfCAD before 3D printing. To do this, go to the Modify Category and select the Simplify Objects tool:
Set the Intensity to 5 and tick the check mark to finalize the operation:
You notice that the number of faces has been reduced to approximately 34k. It is now simpler to work on the simplified model. Isolate the original copy made. Go to the toolbar on the Drawing category and select the 3D Sketch.
Use the Line and click on the highlighted point to drag and draw on the gap on the teeth.
The next step is to edit the created object. Go to the Modify category and select the Round Objects.
On the Round Objects, set the Convert to Spline to true:
We want to create the new section on the front side to fill the tooth gap. To do this, go to the Drawing category, select the 3D Sketch, and activate the Drawing Mode to Object:
This allows you to create the new object, automatically tracing the former drawing on the other side. Then click on the highlighted point to drag and draw the object.
Go to the Modify Category, select Round Objects, and enable the Convert to Spline option.
To this point, there are two profiles. Go to the Tools category and select the Loft Tool.
Upon clicking on the Loft tool, the object is filled as shown below:
Even on the back side, this is how it will look like:
Make a copy of the object:
Select the simplified model and the model of the piece created recently. Select Stitch and Scoop on the toolbar and click to choose the Union tool.
Highlight the original copies go to the Stitch and Scoop category, and select the Union again:
Finalize the Union operation. The next step is to scale the model to how it was originally. Go to the toolbar on Scale tool and activate the Keep Proportion option. Set the Y axis to 19.26:
Now select and Isolate all the models except the Union 2:
You remain with a model with a nicely filled tooth gap:
You have now finally filled the gap in the design.
Fixing Meshes in SelfCAD
If you encounter issues with meshes in SelfCAD, such as holes or other irregularities, you can use the Magic Fix Tool of the program to clean up your scans and optimize them. You can access it in the Tools section.
A slide bar will appear on the left section where you can either increase or decrease the level of details that you would like to appear on the design.
After selecting the value, you can select Preview, and you will see a detailed mesh, as shown below.
In addition to the Magic fix tool, there is also the Simplify 3D tool that you can use to reduce the number of faces or polygons in your scans. Sometimes 3D scans can contain millions of high density polygons and you can use this tool to reduce them and simplify the mesh while still preserving important details. Get to know how to use Simplify 3D in the video below.
You can also use the 3D sculpting tools of SelfCAD to add more details to the 3D models created from 3D scans and you can use them to add missing parts, and even refine the surfaces. SelfCAD also has capabilities to do UV mapping and texture mapping and it also comes with a powerful 3D rendering software useful generating realistic renders of your designs.
When you have prepared your 3D scans, you can also prepare it for 3D printing using the in-built online slicer of SelfCAD and you don’t need to switch to another separate software or install any add-on; you simply click the 3D Print option on the menu bar.
A new window will launch containing various 3D printers. You can choose the one you are using. The slicer of SelfCAD supports most of the common FDM 3D printers.
Apply the various settings for your 3D printer, select the material, and then click Slice to slice the model.
If you use a resin 3D printer, you can save the file as an STL file and then import it to a separate 3D printer slicer that supports that.
Comparing ExoCAD and SelfCAD: Which One Should You Use?
Even though ExoCAD is a specialized CAD software explicitly designed for dental applications and widely used, it has various downsides that make SelfCAD a better option. Below are some of them.
1. Pricing Structure
To access the various software for Exocad, you have to pay thousands of dollars. There is an option for getting a license in two forms: a Flex or a perpetual license. The Flex license is a subscription-based licensing model in which users pay a recurring fee, typically monthly or yearly, to access and use the Exocad software programs. This subscription model allows users to choose the duration for which they need access to the software. It is suitable for those who may not require continuous, long-term access and prefer a more flexible payment structure. On the other hand, Perpetual license provides users with a one-time, upfront payment to purchase the software. With a perpetual license, users own the software indefinitely and are not bound by subscription renewals. This licensing model is suitable for users who plan to use the software consistently over an extended period without needing ongoing subscription payments. - Perpetual licenses often come with an initial maintenance and support period, during which users receive updates and technical support. After this initial period, users may choose to continue with a maintenance subscription to receive ongoing updates and support.
In addition to buying the subscription, users must pay thousands of dollars for addons and modules (described in this article) if they need them in their tasks. You must contact one of their resellers and partners to buy the software, as Exocad does not sell directly. This can be time-consuming, especially if you want to get the software quickly.
For SelfCAD, on the other hand, there are three subscription options: monthly, yearly, or perpetual license you can buy it on the website without using a third party, and it costs only $14.99/m or $139.99/yr. The perpetual license costs only $500; this is much cheaper compared to ExoCAD compared to what you can do with it. Unlike ExoCAD, which doesn’t have a free trial, SelfCAD has a free version that you can use to test the software and see if it fulfills your requirements.
2. The Need for Addons and Modules
As the pricing structure section mentioned, you must have various modules and add-ons to do certain tasks in ExoCAD. Each module provides specialized tools and features for specific tasks. For example, you need to have the Model Creator module to create physical designs from scans. To slice your designs, you will need Exoprint software to prepare them, and then you pass it to Envision One RP using an XML-based interface before proceeding to 3D printing.
Also, you must download presets for your specific 3D printer to work well.
Even though you need to do the integration once, it is quite a lot of steps compared to SelfCAD, which only requires you to select the 3D Print tool, and you will have access to the slicer.
Though the modular system approach for ExoCAD allows you to customize the software environment and make it specific to your workflow demands, it can be expensive and time-consuming if you need many of them. SelfCAD, on the other hand, takes a different approach by providing an all-in-one solution with a comprehensive set of tools within a single platform. Once you purchase one license, you don’t need to purchase an additional module or add-on; instead, it offers a unified interface with a wide range of modeling, sculpting, rendering, mesh fixing, and 3D printing tools. This benefits those who want simplicity and a streamlined workflow without navigating through different modules for various tasks.
3. Complexity of the Program
ExoCAD is complex and it can be overwhelming for beginners. When you visit the website you might be confused as you might find it challenging to discern where to start from. You have to go to the products section in order to choose what you need.
After choosing the product you need,, you must contact resellers and Exocad’s partners to get the license. Also, you will need to install modules to be able to customize it based on your needs and learning all of these takes time. This complexity is attributed to the software's comprehensive nature, accommodating various dental design tasks. SelfCAD on the other hand is simple and easy to use.
Once you launch the software you get started easily and learning how each tool works takes less time too and no need to install any module or add-on as all the necessary tools are available. You also don’t need to contact resellers to get your license.
4. The License is for a Single Computer
Exocad operates on a licensing model that requires a separate license for each computer. This means that if an organization has multiple workstations or staff members using Exocad, they would need to purchase individual licenses for each installation. This is very expensive especially if an organization or company has a big team using the software. SelfCAD, on the other hand, allows for the sharing of licenses among staff members. This is advantageous for collaborative environments where multiple team members may need access to the software and this is cost-effective.
5. Files Storage Issues
Exocad's file sizes can pose challenges when it comes to storage as the files are big. This can lead to issues related to storage capacity and the cumbersome management of these sizable files, and there will be a need to look for more storage to accommodate, especially when one needs a lot of modules. In contrast, SelfCAD offers a cloud-based storage solution that addresses the challenges associated with file storage. By storing all design files in the cloud, it allows for easy access and sharing among team members. This approach also eliminates concerns about local storage limitations, especially for users who may prefer not to install software locally as they can access the software on the browser.
Once you finish creating your 3D models and slicing them, the next step is 3D printing. Below are the two main 3D printing technologies used in dentistry.
1. Stereolithography (SLA)
(Image credit: Howto3dprint.net)
In SLA, a photosensitive liquid resin that is based on the principle of photopolymerization is used. The liquid is cured layer by layer using a laser or light source to build the intended design. A resin 3D printer consists of a resin basin and a build platform. The basin contains the liquid photopolymer resin, and the build platform is positioned above it. The printing process begins with the first layer of the 3D object. The build platform descends into the resin tank, and a laser or light source selectively exposes the liquid resin according to the sliced layer's pattern. The exposed resin solidifies, creating the first layer of the object. After each layer is cured, the build platform is incrementally lifted, and the process repeats for the next layer. This layer-by-layer approach continues until the entire 3D object is created. Under SLA 3D printing, there is a technology called masked stereolithography (MSLA) and it is used in dental 3D printers like NextDent LCD1 from 3D systems. In MSLA, an LCD screen or an array of micro mirrors is used to mask and solidify specific areas of the resin selectively. The screen or mirrors act as a mask, allowing the UV light to pass. The masked approach means that an entire layer can be cured simultaneously making it faster as compared to the other general SLA 3D printing technologies.
Once the printing is complete, the object is carefully removed from the resin and the post-processing activities follow. SLA is good due to its superior precision and finer layer resolution. In dental applications where accuracy is paramount, SLA's layer-by-layer curing process using a liquid photopolymer resin results in exceptionally detailed dental models and this level of precision is especially crucial for the designs where the intricate details can significantly impact the success of the procedure.
2. Digital Light Processing (DLP)
(Image credit: TheFabricator)
DLP operates on the principle of VAT photopolymerization. DLP 3D printers utilize a digital light projector that is equipped with a digital micromirror device or an LCD ro project layers of the models onto a vat of a liquid photopolymer resin simultaneously. The process begins with the projection of the desired cross-section of the design onto the resin. The exposure to UV light initiates the photopolymerization process which causes the resin to solidify and adhere to the build plate. The build platform then moves down, allowing the successive curing of each layer until the entire 3D object is formed.
The high resolution of DLP 3D printers enables the creation of detailed and accurate designs with fine details. It’s also mostly used in dental laboratories to create crowns and bridges as well as temporary and permanent dental implants. Biocompatible dental resins are the materials used in this technology, mostly as they meet standards for patient safety.
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