Daniel Jankovič / cotu s.r.o.
MUDr. Josef Kunkela, Ph.D. / KUNKELA Clinic s.r.o.
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Are you interested in the topic of post-processing and health safety in 3D printing?
Enhance your knowledge and gain practical insights at a professional webinar taking place on March 19, 2025, led by Daniel Jankovič (cotu s.r.o.) and MUDr. Josef Kunkela, Ph.D. (KUNKELA Clinic s.r.o.). Register for the webinar here.
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The quality, durability, and biocompatibility of 3D prints depend not only on selecting the right 3D printer and the appropriate material but also significantly on proper post-processing.
If you are still unsure about which 3D printer to choose, more details about their specifications can be found in this article. Modern DLP 3D printers offer highly precise and long-term stable 3D prints thanks to the correct wavelength and continuous monitoring of the printing environment using sensors. Their open system allows working with a wide range of modern materials and procedures, providing greater flexibility in 3D printing and increasing production efficiency.
Besides choosing the right 3D printer, selecting high-quality dental materials and their proper indication is equally important. Brands like Asiga, Detax, KeyPrint and Pro3dure offer reliable and certified products that meet the highest medical standards. Thanks to a wide range of materials and years of market experience, they provide certainty for every dental practice or laboratory. If you need advice on choosing the right technology or materials, feel free to contact us. With our hands-on experience in 3D printing, we can provide verified procedures directly from real clinical applications. Your goal is to produce and deliver high-quality prosthetic products. Our goal is to recommend the right technology based on your requirements and working conditions, install it, train you, set up a safe production process, provide all necessary MDR documentation, and demonstrate the workflow in a dental practice and laboratory.
In this article, we will take a detailed look at the individual steps of post-processing—from cleaning to final adjustments. Our clinical and technological experience has proven that mistakes and shortcomings in the final steps of 3D printing degrade all your efforts and investments and can pose health risks to patients. We will explain the importance of each step in achieving the desired aesthetics, mechanical strength, and biocompatibility of additively manufactured prosthetic products.
Fig. 1 - 3D-printed denture base with supports after cleaning.
Post-Processing Phases
1. Cleaning
After printing, it is essential to remove residual uncured resin from the surface of 3D prints, as it can be cytotoxic. This is usually done using cleaning solutions, ideally in an ultrasonic cleaner. Thorough cleaning ensures the biocompatibility of the final dental work. After cleaning, 3D prints must be allowed to ventilate (evaporate) due to the absorption of the cleaning medium deep beneath the surface of the print.
2. Curing (Polymerization)
This step ensures full material polymerization, increases mechanical strength and enhances biocompatibility. Curing is performed using ultraviolet (UV) light, with biocompatible materials requiring specific conditions, such as curing in a protective atmosphere to prevent oxygen bonding or additional heat curing.
3. Finishing Work
Grinding, polishing, potential coloring, and final surface sealing ensure a natural and aesthetic appearance of dental prosthetics. Quality control guarantees that the finished replacements fit well and meet all aesthetic and mechanical requirements.
To achieve optimal results and ensure patient safety, it is essential to carefully follow all post-processing phases. Proper procedures guarantee the material's certified properties and the biocompatibility of the final dental work. Manufacturers of biocompatible materials must declare verified working procedures in the material safety data sheet (MSDS) or instructions for use (IFU). These recommended protocols are binding and must be followed
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Fig. 2 - Instructions for Use (IFU) for Detax Freeprint temp material for making temporary restorations, contains manufacturer-tested equipment used for 3D printing and post-processing – the so-called guaranteed workflow.
Methods and Procedures:
Cleaning of Dental Prints
Proper cleaning of 3D prints is essential for patient safety. Residual resin on the surface of 3D prints is not visible to the naked eye but leaves a sticky film that can be cytotoxic, causing irritation or allergic reactions. To minimize this risk, we recommend using an ultrasonic cleaner instead of a vortex cleaner. Ultrasonic cleaning with an appropriately set wavelength (40 kHz) effectively and quickly removes resin even from hard-to-reach areas and cavities.
Cleaning occurs in two or three baths: rough cleaning and final rinsing in a clean solution. Typically, 3D prints are placed in a floating container with isopropyl alcohol (IPA) inside a water bath in an ultrasonic cleaner.
Fig. 3 - The print is cleaned in an ultrasonic cleaner for 2 minutes in the first bath (rough cleaning), followed by 2 minutes in the second bath (final cleaning). Before curing, it is dried with compressed air and left to ventilate for 1 hour.
IPA as a Cleaning Agent
IPA is an effective cleaning agent, but it also causes material brittleness, leading to reduced durability of 3D prints. Therefore, cleaning time in an ultrasonic cleaner should be limited to a maximum of 5 minutes. The process can be optimized by heating the cleaning solution, which enhances its effectiveness. Most ultrasonic cleaners now include this feature. The recommended cleaning time is 2 minutes for rough cleaning and 2 minutes for fine cleaning.
Alternative Cleaning Agents
For dental work requiring greater durability, such as crowns, bridges, splints, or removable prostheses, we recommend using alternative cleaning agents like Saremco Cleaning Concentrate. This product is specifically designed for cleaning dental work, effectively removing residual resin while being gentler on the printed material, preserving mechanical strength, and allowing for extended cleaning up to 8 minutes. Any remaining cleaning agent is then removed in a second bath with IPA for one minute.
After completing the two-phase cleaning process, prints must be thoroughly dried with compressed air to remove all chemical residues. Allowing 3D prints to ventilate after cleaning significantly increases their mechanical durability. Next, the prints are cured either at room temperature for at least one hour or for 30 minutes at 40°C in a laboratory dryer.
Thorough cleaning is essential not only for achieving an aesthetically perfect result but also for ensuring the biocompatibility and durability of 3D prints.
Curing of Dental Prints
Following cleaning, another crucial phase is curing (polymerization) of the ventilated 3D print in specially designed devices. This ensures mechanical strength and biocompatibility.
In principle, 3D prints are always exposed to UV light to polymerize the material on the surface. Standard curing times for dental models in basic curing units with lower power take 15-30 minutes.
For maximum biocompatibility, curing should be performed in the broadest possible UV light spectrum, particularly at a 385 nm wavelength. This wavelength ensures complete breakdown of the photoinitiator, reducing shrinkage and enhancing mechanical properties.
Curing in Nitrogen Atmosphere
Biocompatible materials require curing without oxygen exposure to prevent cytotoxic inhibition layers. This can be achieved by curing in a nitrogen environment or vacuum. Some devices, such as Photopol (Dentalfarm), first create a vacuum in the polymerization chamber before filling it with nitrogen, ensuring low nitrogen consumption while achieving complete curing in minutes.
Hybridní systém
U některých dentálních materiálů může být použita kombinace UV a termálního vytvrzení, tzv. hybridní systém. Zde je ale problém absence ochranné atmosféry. Toto lze řešit vytvrzením 3D výtisku v glycerinu v průhledné nádobě. Avšak je nutné zdůraznit, že ne všechny materiály na něj reagují optimálně a tento proces zpomaluje šíření UV světla i tepla. Pro nejlepší výsledky doporučujeme 3D výtisk nejdříve krátce vytvrdit v ochranném prostředí, až poté v hybridním systému. Materiály vhodné pro vytvrzování tímto způsobem jsou např. Lucitone Digital Print Denture (Dentsply Sirona).
Výběr zařízení, časování a postup je potřeba dodržovat podle doporučení výrobců materiálu - resinu. Ti často v návodech uvádí vytvrzování v dusíkovém prostředí. Některá zařízení disponují obojím, např. Photopol (Dentalfarm). Tento přístroj nejdříve vytvoří v polymerační komoře vakuum a následně do ní napustí dusík. Tím je dosažena velmi nízká spotřeba dusíku. Vysoký světelný výkon společně s přeneseným teplem dělají z tohoto zařízení univerzální a bezpečný polymerátor.
Fig. 4 - The printed and assembled removable prosthesis is cured in the Photopol (Dentalfarm) device, which features high-power UV light and a protective nitrogen atmosphere.
Final Processing: Aesthetics and Functionality
After curing, final processing takes place. Grinding and polishing smooth the surface to remove minor imperfections and ensure a flawless finish. To achieve a natural look, additional coloring can be applied. Techniques like "candy coating" or sealants such as Palaseal (Kulzer) enhance the final surface.
Impact of Post-Processing on Dental Prints
As we have seen, post-processing plays a crucial role in the quality, aesthetics, safety, and long-term functionality of dental prints. Proper cleaning and curing ensure durability, preventing cracks, fractures, premature wear, or unwanted discoloration. The smooth surface quality affects both aesthetics and hygiene by minimizing plaque buildup and simplifying cleaning.
By following precise post-processing protocols, dental professionals can ensure high-quality, safe, and long-lasting 3D-printed prosthetics for their patients.
Common Issues in Improper Post-Processing
Common problems that can arise from improperly performed post-processing include:
- Insufficient Surface Cleaning – This can lead to a reduction in the surface area of the internal parts of crowns, bridges, or removable dentures, resulting in difficulties with the fit of the prosthetics to the preparation margin or mucosal relief.
- Overexposure to IPA Bath – Excessive cleaning in an IPA bath weakens the prints, causing brittleness and cracking. This phenomenon can be identified by the so-called "chalking effect," where the surface of printed prosthetics appears powdery
Fig. 5 - Chalking effect on printed denture teeth caused by exceeding the recommended cleaning time in IPA.
- Insufficient Drying Time – If the drying time is too short, the deeper layers of the resin remain insufficiently polymerized, making them prone to cracking and deformation. This problem is often compounded by failure to adhere to the recommended thickness of fixed restorations (crowns and bridges) or removable denture bases.
Fig. 6 - Inadequate drying of a printed and subsequently cleaned crown removed from the IPA bath caused the resin to cure only on the surface, preventing complete (deep) polymerization of the restoration.
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Inadequate Curing (Polymerization) – Insufficiently cured 3D prints can lead to mucosal irritation and compromised biocompatibility of the material, increasing the risk of allergic reactions or infections in the oral cavity.
- Uneven Curing – This results in the deformation or shrinkage of 3D prints and weakens their mechanical properties. This may lead to premature wear, cracking of the dental restoration, or improper fit on the tooth.
Fig. 7 - Uneven curing in a low-quality curing unit caused resin shrinkage of the crown restoration by more than 0.1 mm (measured from the preparation margin) despite adhering to the curing time.
Innovations in Post-Processing
In the field of post-processing for dentistry, automated systems are becoming increasingly popular, simplifying and enhancing precision throughout the process. Modern "all-in-one" units for cleaning and curing minimize unpleasant fumes and messy work, making them a better solution for dental practices. However, their downside is a longer processing time (as ultrasonic cleaning cannot be used) and compatibility limited to selected materials and indications.
Other significant innovations include materials cured using a hybrid method—combining ultraviolet light and heat—which enhances mechanical durability. Another innovation involves environmentally friendly cleaning solutions that replace traditional chemicals, reducing the ecological footprint of the entire process and increasing safety during handling.
Eco-Friendly Waste Disposal
When cleaning 3D prints, it is crucial to consider environmentally friendly waste disposal. The waste generated contains highly toxic chemicals that are harmful not only to human health but also to the environment, particularly aquatic ecosystems.
Users of water-washable resins often overlook this issue and improperly dispose of contaminated water in sinks. Exposing the diluted material to UV light does not fully solve the problem, as the material never completely polymerizes. Proper waste disposal is essential to protect nature, ensure a safe future, and comply with legal regulations.
For eco-friendly waste disposal, you can contact your biological waste management company. We are happy to assist with waste classification and provide guidance on how to handle and dispose of such waste safely and correctly.
Conclusion: Post-Processing as the Key to Health and Quality in Dental 3D Printing
The quality of post-processing plays a crucial role in dental 3D printing. Thorough cleaning, proper curing, and meticulous finishing are essential attributes for meeting strict clinical standards. Innovations in this field not only enhance efficiency but also contribute to higher-quality and safer prosthetic products. Investing in modern technologies and strictly following correct procedures (not only in post-processing) ensures a high standard of healthcare.
Are you interested in the topic of post-processing and health safety in 3D printing?
Enhance your knowledge and gain practical insights at a professional webinar taking place on March 19, 2025, led by Daniel Jankovič (cotu s.r.o.) and MUDr. Josef Kunkela, Ph.D. (KUNKELA Clinic s.r.o.). Register for the webinar here.
Literature:
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Evaluation of dimensional accuracy and degree of polymerization of stereolithography photopolymer resin under different postpolymerization conditions: An in vitro study
Awutsadaporn Katheng, Manabu Kanazawa, Maiko Iwaki, Shunsuke Minakuchi
Journal of Prosthetic Dentistry, Vol. 125, Issue 4, p695–702 -
Influence of postprinting cleaning methods on the cleaning efficiency and surface and mechanical properties of three-dimensionally printed resins
Ok Hyung Nam, Sang-Yeop Chung, Hong-Keun Hyun, Ju Ri Ye, Yuwon Jeong, Seo-Eun Oh, Yong Kwon Chae, Hyeonjong Lee
Journal of Prosthetic Dentistry, Vol. 132, Issue 4, p838.e1–838.e9 -
Influence of postpolymerization time and atmosphere on the mechanical properties, degree of conversion, and cytotoxicity of denture bases produced by digital light processing
Won-Jun Lee, Ye-Hyeon Jo, Hyung-In Yoon
Journal of Prosthetic Dentistry, Vol. 130, Issue 2, p265.e1–265.e7