Potential health problems of monomer based 3D resins
3Dresyns is globally the first and only 3D resin supplier selling "monomer free" biocompatible 3D resins, colors and additives with Material Safety Data Sheets (MSDSs) with non toxic raw materials and without any toxicity risk hazard pictograms. Our "monomer free" reactive resins do not contain any monomers as supplied. They have been designed to reduce the risk of monomer extraction.
3Dresyns portfolio includes monomer based biocompatible 3D resins for biomedical, orthodontic and dental applications which use safe bio monomers for maximum safety.
Why some "biocompatible" monomer based 3D resins can be toxic before and even after printing and postprocessing?
Let´s review different findings published in academia about the toxicity of some commercial 3D resins even after printing and postprocessing:
As clearly highlighted in the last mentioned scientific paper published by the Northwestern University (Chicago, USA), Formlabs’ Dental SG and LT Clear printed in Form 2 SLA 3D printer were toxic, despite being certified as biomedical devices.
This publication "The Biological Effects of 3D Resins Used in Orthodontics: A Systematic Review" concluded that although these resins are considered biocompatible, they exhibit reproductive toxicity in mouse oocytes after direct and indirect exposure. The tested resins were Formlabs Dental SG resins (DSG) and Dental LT Clear (DLT), classified as biocompatible for medical use and currently used in dental surgical guides and oral retainers.
Conclusions: Within the scope of this review, it was noted that studies evaluating the biological effects of 3D resins in orthodontics are mostly conducted in vitro. Although mixed results are described, 3D printed aligners may present higher levels of cytotoxicity and genotoxicity when compared to thermoplastic resins, particularly those that have not been subjected to a final surface treatment. As such, clinical studies analyzing saliva, blood, or even urine samples must be carried out in the future to determine the levels of monomers released in humans upon the use of these devices.
In this publication: Evaluation of dimensional accuracy and degree of polymerization of stereolithography photopolymer resin under different postpolymerization conditions: An in vitro study the degree of polymerization of a Clear Formlabs 3D resin was evaluated following Formlabs printing and postprocessing protocol. Several specimens were cleaned with isopropanol in the Form Wash unit (Formlabs) for 15 minutes to remove excess resin and poscured with Formlabs light box Form Cure at 15 and 30 minutes and at 40, 60, and 80 ºC. The results are shown in the following table:
The degree of polymerization for all the postprocessing conditions is in between 70 and 90%, which confirms that the % of residual uncured monomer is between 10 and 30%. The % of residual uncured monomer is extremely high and can leach out from the prints and be absorbed by humans, causing potential cytoxicity, genotoxicity, and potential health problems.
The Quality requirements of class I & II biomedical devices, including dental devices, such as FDA, ISO 20795, 13485 & 10993, limit the residual monomer content to <0.1%, which is much far below the 10-30% already reported. The residual monomer in liquid state trapped inside the solid printed device is prone to leach out, be extracted by saliva, and absorbed by the mucosa.
Which is the risk of trapped residual monomers and other chemicals in printed devices for human health?
The answer depends on the type and concentration of physically trapped monomers and other leachables and extractables in the medical devices.
How can the risks for humans be figured out?
By reading the MSDSs of the liquid 3D resins as supplied, and the individual risks and hazards of their monomers, and other ingredients since they are leachable, and extractable if uncured or physically trapped "non bound" to the device.
- For more information read: Biocompatibility hints
- These findings confirm the importance of using 3Dresyns monomer free 3D resins
Similarly to the previously reported findings, the resin of Graphy for direct printing of aligners also may raise concerns on potential health hazards as reported in this paper published in the European Journal of Orthodontics: Leaching from a 3D-printed aligner:
"Although efficiently polymerized and BPA free, the great variability in the amount of UDMA monomer leached from the examined samples may raise concerns on potential health hazards after repeated intraoral exposure"
3Dresyns statement:
The biocompatibility failure of the mentioned commercial resins might have happened to any biocompatible resin, even to the most biocompatible resins if and when would not had been properly printed and postprocessed.
Conclusion
Biocompatibility and safety failure can be due to an inadequate resin design from its conception (eg by using toxic raw materials), or due to an inadequate printing, postcuring, and postprocessing equipments and practices, leaving the prints with leachables and extractables, unreacted free monomers, residuals and reaction byproducts.
On one hand, 3D resin suppliers are responsible for using as safe as possible raw materials, while on the other hand 3D printed medical device manufacturers are responsible of designing and implementing appropriate workflows to ensure that their medical devices are safe and free of leachables and extractables beofre commercialization.
Photopolymer 3D resins are liquid photo reactive raw materials, not certified medical devices, which photopolymerise or react with light in the printers, normally layer by layer, to become printed solid photopolymer materials with specific shapes.
Biocompatible 3D printed medical device need to be manufactured properly without leachables and extractables after appropriate design, printing, postcuring, and postprocessing workflows to ensure maximum quality and safety for final users.
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Customisation
3Dresyns custom designs biocompatible 3D resins, post processing protocols, and quality controls to meet the most demanding specifications, without hazards, nor risks, for printing safe biomedical devices, food packaging, and toys.
You may contact us to consult about our customisation services of biocompatible synthetic and bio-based 3Dresyns and your specific performance goals at: info@3Dresyns.com
Learn more about Certification of biomedical devices and food packaging