Academy
Direct 3D Printing of Clear Aligners: Future or a Dead-End?
Clear aligners have become a trusted solution for orthodontic treatment, offering a discreet and patient-friendly alternative to traditional braces. Their aesthetic appeal, removability, and predictable results make them a preferred option for many seeking bite correction.
Most aligners today are produced using a well-established workflow that includes 3D printing of dental models followed by thermoforming—a process where a heated plastic sheet is vacuum-formed over each model to create the aligner.
However, a new technology has entered the scene: direct 3D printing of clear aligners. Instead of printing physical models, this approach allows the aligners themselves to be printed directly using specialized 3D printers and biocompatible resins. This innovation raises a key question: is direct printing the next big step in orthodontics, or is it an experimental path with limited potential? Let’s explore this technology.
Key Features of Directly Printed Aligners
Directly printed aligners (also known as DPAs) represent a new frontier in orthodontic technology, first introduced in 2021. Unlike traditional aligners that require a printed model and thermoforming, DPAs are created directly from digital files, eliminating intermediate steps.
These aligners are produced using UV-curable polymer resins in a nitrogen environment, which prevents oxygen from interfering with the curing process. The result is an aligner that is more resistant to heat and features shape memory, maintaining its intended form and force throughout wear.
Workflow of Direct Aligner Printing
Data Collection
The first step involves acquiring detailed digital records of the patient’s oral anatomy. This includes:
-
3D intraoral scans
-
photographs
-
CBCT data (if needed)
These records are an essential part of the digital treatment plan for any kind of aligner bite correction—thermoformed or directly printed.
Digital Design and Treatment Planning
Using specialized orthodontic software, the clinician or lab technician creates a step-by-step treatment plan. Each stage of the treatment corresponds to a uniquely shaped aligner. This is where tooth movement simulation and final outcome visualization happen.
Adding Support Structures
Before printing, support structures are digitally added to the aligner models. These supports are crucial for stabilizing the object during the 3D printing process, ensuring proper shape and alignment of thin walls and complex contours. Similar support structures are also used in models for traditional thermoformed aligners.
Direct 3D Printing with Polymer Resin
The aligners are then printed directly using UV-curable liquid polymer resin in a closed nitrogen chamber. Printing in a nitrogen-rich environment prevents oxygen from interfering with the curing process, leading to greater mechanical strength and precise shape fidelity.
This stage typically uses resin-based 3D printers, such as those operating on Digital Light Processing (DLP) or Stereolithography (SLA) technologies.
Post-Processing
Resin Removal
Once printed, aligners contain residual uncured resin. They are placed into a centrifuge with a built-in heater, which gently spins the aligners to remove excess resin. Some systems allow recycling and reuse of the collected resin, reducing waste and cost.
Support Removal
After cleaning, support structures are manually removed. This step requires care to avoid damaging the aligner’s shape or surface quality, especially in areas with fine detail.
UV-Curing
Aligners then undergo final curing in a specialized UV-light chamber, completing the polymerization process. This enhances the material’s mechanical properties, giving the aligner the necessary strength and shape memory.
Polishing Contact Areas
Finally, the contact points where supports were attached are carefully polished. This step ensures patient comfort and safety by removing any rough edges or imperfections.
Brands in Direct Aligner Printing
At the moment, two companies lead the market of directly printed clear aligners: Graphy and LuxCreo. Both offer full in-house ecosystems for the production of aligners — from software and resins to specialized 3D printers and post-processing equipment.
Graphy
Graphy is a South Korean company that focuses on photo-curable resins for 3D printing. Key features:
-
Graphy develops its own proprietary resins and holds source technology patents in 3D printing materials
-
Graphy's materials and workflows are FDA-approved in the U.S. and CE-certified in Europe, allowing safe clinical use.
-
Graphy offers a complete solution for direct aligner printing, including its own line of printers, UV-curing units, and dedicated resin systems.
LuxCreo
LuxCreo is a U.S.-based dental tech company.
-
4D Aligner™ Technology: LuxCreo brands its aligner solution as «four-dimensional», emphasizing shape memory and adaptive fit as a distinctive feature.
-
Their system is designed for in-office or centralized production of custom aligners.
-
Like Graphy, LuxCreo provides printers, proprietary resins, post-processing hardware, and treatment design software.
-
Their materials are also
Challenges in Direct 3D Printing of Clear Aligners
While directly printed aligners represent a major technological advancement, their use still presents several limitations and practical challenges. These include issues with post-processing, material properties, clinical handling, and biological safety — all of which slow down their widespread application.
Support Removal and Surface Quality
Directly printed aligners require support structures during the printing process to stabilize thin areas and overhangs. These supports are in direct contact with the aligner surface and must be carefully removed after printing. However, this support removal process is time-consuming, and improper handling can leave visible marks, rough edges, or material defects, potentially affecting patient comfort and fit.
High Equipment Demands and Limited Scalability
Directly printed aligners require specialized equipment, including DLP or SLA 3D printers, nitrogen-assisted UV curing chambers, and centrifuges with built-in heaters to remove excess resin. The entire process must take place in a highly controlled lab environment. Compared to traditional thermoforming, this setup is significantly more complex and costly. In addition, proper waste management and safe recycling of leftover resin are essential — any missteps can pose safety risks.
Because of these strict requirements, scaling up production is currently difficult, limiting the technology’s practicality for high-volume orthodontic labs and clinics.
Rigid and Less Flexible Material Properties
Studies show that directly printed aligners, such as those made from Tera Harz TC-85, are stiffer and less flexible than thermoformed counterparts. They demonstrate lower flexural strength and reduced bending capacity, especially at temperatures of the oral cavity. Although they have some degree of shape memory and consistent force delivery, this comes at the cost of reduced elasticity.
Higher Risk of Allergic Reactions
Despite FDA and CE certifications, directly printed aligners are made of photo-curable resins, which are more chemically active than thermoplastics used in vacuum-formed aligners. Clinical reports have noted:
-
Moderate burning sensations and minor tissue reactions in several patients.
-
Concerns over incomplete resin curing, which can leave residual monomers like urethane dimethacrylate.
-
Increased porosity, which may lead to higher bacterial colonization, biofilm formation, and potential irritation of oral soft tissues.
Strict adherence to manufacturer guidelines is essential to avoid these side effects, but the risk still exists — especially in in-office production environments where standardization is difficult to maintain.
Limited Research and No Standard Protocols
Directly printed aligners are still a new technology, and research on them is limited. Most studies are small and based on single doctors or software systems.
Important questions — like how often aligners should be changed, whether attachments are needed, and how well they work in complex cases — still don’t have clear answers. Without strong clinical data, many orthodontists are hesitant to use this technology widely.
Advantages of Directly Printed Aligners
While there are significant challenges in the use of directly printed aligners today, the technology holds remarkable potential to transform aligner manufacturing in the future.
Customizable Thickness and Force Control
One of the most promising advantages is the ability to adjust aligner thickness at specific points, especially in the cervical region. This allows clinicians to program localized force application where it’s needed most, enhancing treatment efficiency and reducing the need for auxiliary features like attachments. This level of customization is impossible with thermoforming, where material thickness is determined by the original plastic sheet and often thins out in critical zones during forming.
Design Freedom for Complex Geometries
Direct printing enables the creation of complex and non-uniform structures, including depressions, undercuts, retention features, and micro-textures for force modulation. These elements can be embedded into the aligner itself, allowing for more precise force vectors and potentially better control over difficult tooth movements, such as rotations or torque, without relying solely on attachments.
Shape Memory Effect
When deformed, the aligner can recover its shape by being placed in warm water (45–50 °C). They can also be disinfected in hot water without losing form, unlike thermoformed aligners, which would permanently deform under the same conditions.
Conclusion
Directly printed aligners represent an exciting evolution in orthodontic technology, offering new possibilities in design precision, force control, and material behavior. However, this approach is still in its early stages, with limited clinical data and several practical challenges — from equipment requirements to post-processing complexity and potential biocompatibility concerns.
At this stage, there is no clear reason to fully replace traditional thermoformed aligners. Yet, as research advances and workflows mature, direct 3D printing may become a powerful tool, especially for specific cases like finishing, relapse correction, or experimental protocols demanding high customization.
