A Dentist’s Guide to Biocompatible Resins: Navigating FDA & ISO Standards in 3D Printing

The world of dentistry is rapidly evolving, with 3D printing technology at the forefront of innovation. From surgical guides to custom splints and even denture bases, additive manufacturing is transforming how you deliver patient care. But with this exciting technology comes a critical responsibility: ensuring the materials you use are safe, compliant, and truly biocompatible.

As a dental professional, you’re committed to the highest standards of patient safety. When incorporating 3D printed devices into your practice, understanding the complex landscape of medical resin classification, regulatory frameworks, and biocompatibility testing is no longer optional—it’s essential. This guide is designed to demystify these topics, providing you with the knowledge to confidently select and use medical resins, ensuring both patient well-being and regulatory adherence. We’ll explore how bodies like the FDA and EU authorities classify devices, dive into crucial standards like ISO 10993, and look at practical examples of resins used in modern dentistry.

Understanding the Regulatory Maze: FDA and EU MDR for Dental Devices

When you choose a resin for a dental application, it’s crucial to remember that regulatory bodies like the U.S. Food and Drug Administration (FDA) and European authorities (under the EU Medical Device Regulation – MDR) classify the final medical device you create, not primarily the resin itself.⁵ The resin is a component material, and its suitability is assessed in the context of the device’s intended use and risk profile.

European Union: Medical Device Regulation (EU MDR – Regulation (EU) 2017/745)

The EU MDR (Regulation (EU) 2017/745) provides a comprehensive framework for medical devices in the EU market. It uses a risk-based classification system, detailed in Article 51 and Annex VIII.¹ Dental devices, like all medical devices, fall into one of four main classes:

• Class I: Low risk (e.g., many non-invasive devices, some try-in models).
• Class IIa: Low to medium risk (e.g., many dental splints, short-term mucosal contact devices).
• Class IIb: Medium to high risk (e.g., some longer-term intraoral devices, certain implantable components).
• Class III: High risk (e.g., devices with significant systemic interaction, though less common for typical 3D printed dental resins).

The manufacturer (which could be your dental lab or even your practice, if you’re 3D printing final devices) is responsible for correctly classifying the device based on its intended purpose and the 22 classification rules in Annex VIII.¹ These rules consider factors like how long the device will be in contact with the patient (transient, short-term, long-term), how invasive it is, and if it has special characteristics.²

The EU MDR also has specific sub-categories for Class I devices that require Notified Body oversight for certain aspects ¹:

• Class Is (Sterile): Devices supplied sterile (e.g., a sterile surgical guide). The sterility aspect needs Notified Body certification.¹
• Class Im (Measuring Function): Devices with a measuring function. Certification is needed for metrology aspects.¹
• Class Ir (Reusable Surgical Instruments): Reusable instruments requiring Notified Body certification for reuse aspects (cleaning, sterilization, etc.).¹

For dental devices falling into Class IIa, IIb, and III, a conformity assessment by a Notified Body is mandatory before they can be CE marked and sold.¹ The higher the class, the more rigorous the assessment. This detailed EU system influences how you approach material selection and the necessary documentation for your 3D printed dental applications.²

United States: Food and Drug Administration (FDA) Classification

In the U.S., the FDA’s Center for Devices and Radiological Health (CDRH) regulates medical devices, categorizing them into three classes based on the level of control needed to ensure safety and effectiveness ¹¹:

• Class I (General Controls): These devices pose minimal risk. General controls include good manufacturing practices (GMP) and proper labeling. Many Class I devices are exempt from premarket notification (510(k)).⁶ Examples relevant to dentistry might include some impression trays or basic diagnostic models.⁸
• Class II (General Controls and Special Controls): These are moderate-risk devices. Special controls can include specific performance standards or postmarket surveillance. Most Class II dental devices, like many restorative materials or surgical guides, require a Premarket Notification 510(k) to show they are “substantially equivalent” to an existing legally marketed device.⁶
• Class III (General Controls and Premarket Approval): These are high-risk devices, often those that are life-supporting, implantable, or pose a significant risk of illness or injury. They usually require Premarket Approval (PMA), a very comprehensive submission with extensive data, including clinical data.⁶ While many common 3D printed dental applications won’t hit this level, some advanced implantable materials might.

The FDA’s system, while also risk-based, uses broader categories than the EU MDR’s detailed sub-rules.⁶ This means a dental device might have slightly different pathways or evidentiary requirements depending on whether you’re targeting the US or EU market.

The Gold Standards: Biocompatibility Testing (ISO 10993 & USP Class VI)

“Biocompatible” is a term you’ll see frequently, but what does it truly mean for your dental practice? Biocompatibility is the ability of a material to perform its intended function within the body without causing any harmful local or systemic effects.⁷ For dental resins that come into contact with oral tissues, saliva, and sometimes blood, this is non-negotiable.

ISO 10993: The Global Benchmark for Biological Evaluation

The ISO 10993 series, “Biological evaluation of medical devices,” is the globally recognized standard for assessing biocompatibility. It’s not just a checklist; it’s a risk-based approach.⁷ ISO 10993-1 (“Evaluation and testing within a risk management process”) emphasizes that the evaluation must consider the chemical nature of the materials, the type and duration of body contact, and the device’s intended use.⁸

Dental devices are categorized based on:

• Nature of body contact: E.g., surface devices (contact with skin or mucosal membranes like most dental appliances) or implant devices.⁷
• Duration of contact:

• Limited: <24 hours (e.g., a try-in, some surgical guides).⁷
• Prolonged: 24 hours to 30 days (e.g., orthodontic splints, temporary restorations).⁷
• Permanent: >30 days (e.g., permanent crowns, denture bases, long-term implant components).⁷

This categorization helps determine which biological tests are relevant. For dental resins, some key parts of ISO 10993 include ⁸:

• ISO 10993-5 (Cytotoxicity): Assesses if the material is toxic to living cells. This is a fundamental test for almost all dental resins that will have tissue contact.⁸
• ISO 10993-10 (Irritation and Skin Sensitization): Evaluates the potential to cause irritation or allergic reactions. Crucial for materials in contact with oral mucosa or skin.⁸
• ISO 10993-11 (Systemic Toxicity): Checks for toxicity in organs and tissues away from the contact site, important if substances could leach from the dental device.⁸
• ISO 10993-3 (Genotoxicity, Carcinogenicity, Reproductive Toxicity): Assesses risks of genetic damage, cancer, or reproductive harm. More critical for long-term or permanent contact dental devices.⁸
• ISO 10993-18 (Chemical Characterization): Involves identifying and quantifying the chemical constituents of the material, including what might leach out (extractables and leachables).⁸ This “chemistry-first” approach is increasingly important for understanding potential risks.
• ISO 10993-17 (Allowable Limits for Leachable Substances): Works with ISO 10993-18 to assess the toxicological risk of any identified leachables.⁵

Understanding which ISO 10993 tests a resin has passed gives you a much clearer picture of its safety profile for specific dental applications.

USP Class VI: A Baseline Indicator

The United States Pharmacopeia (USP) also provides standards. USP Class VI is one of the most stringent classifications for plastics, requiring materials to pass a series of in vivo biological reactivity tests.⁷ These typically include systemic toxicity, intracutaneous reactivity, and implantation tests.

While USP Class VI is a good indicator of a material’s general inertness, it’s often considered a minimum requirement or a baseline screening.⁷ It doesn’t offer the comprehensive, risk-based evaluation of ISO 10993 for all potential biological effects relevant to every dental device. So, while a dental resin with USP Class VI certification is positive, it usually doesn’t replace the need for further evaluation according to ISO 10993, especially for devices with more critical or long-term patient contact.⁹

Dental Resins in Action: From Class I to Class IIa and Beyond

Let’s look at how these classifications and standards apply to resins commonly used in 3D printing for dental applications. The intended use of your final printed dental device dictates the resin’s required characteristics.

Class I Resins in Dentistry / Limited Contact Applications

Class I devices generally pose the lowest risk and often involve limited contact, such as with intact skin or short-term mucosal contact.⁴

• Dental Device Examples:

• Surgical guides for dental implant placement.⁸
• Anatomical models for diagnosis or surgical planning (minimal contact).⁹
• Dental try-in devices to check fit and aesthetics before final prostheses.⁸
• Components of custom trays or short-term orthodontic appliances.

• Resin Characteristics & Biocompatibility:
  Resins for these uses typically need to pass ISO 10993-5 (cytotoxicity) and ISO 10993-10 (irritation and sensitization).8 Dimensional accuracy and adequate strength are key for guides and models.
• Resin Examples:

• NextDent Try-In (3D Systems): A Class I material (EU) meeting ISO 10993-1, used for dental try-ins.⁸
• Keyprint Key Guide (Keystone Industries): A Class I resin (EU) meeting ISO 10993-1, -5, and -10, for fabricating surgical guides.⁸
• Regulatory Nuances:
  Even for Class I, if a device is supplied sterile (Class Is under EU MDR), like a sterilized surgical guide, the resin must withstand sterilization without losing its properties or releasing toxic residues. This aspect requires Notified Body oversight in the EU.1

Class IIa Resins in Dentistry / Short to Medium-Term Contact Applications

Class IIa devices (EU MDR) or many FDA Class II devices involve low to medium risk and may have more intimate or prolonged contact, such as with mucosal membranes or breached skin, or short-term presence within the body.¹

• Dental Device Examples:

• Dental splints and retainers.⁸
• Removable denture bases.⁸
• Certain temporary crowns and bridges.
• Devices for short-term mucosal membrane contact (less than 24 hours).⁹
• Some orthodontic aligners.

• Resin Characteristics & Biocompatibility:
  These demand more extensive biocompatibility testing. Beyond ISO 10993-5 and -10, tests may include systemic toxicity (ISO 10993-11).8 For longer contact within this class, genotoxicity (ISO 10993-3) might be considered. Chemical characterization (ISO 10993-17, -18) becomes more important.8 USP Class VI is common.9 Properties like flexibility (for splints), durability (for denture bases), and resistance to the oral environment are crucial.
• Resin Examples:

• NextDent Denture 3D+ (3D Systems): A Class IIa resin (EU) meeting ISO 10993-1, -5, and -11, for removable denture bases.⁸
• NextDent Ortho Flex (3D Systems): A Class IIa material (EU) compliant with ISO 10993-1, -3, -5, -10, -11, -17, and -18, for dental splints and retainers.⁸
• Keysplint Soft (Keystone Industries): A Class IIa resin (EU) (ISO 10993-1, -5, -10) for flexible bite splints.⁸
• Formlabs BioMed Clear Resin: Suitable for long-term skin or mucosal membrane contact, USP Class VI certified, supported by an FDA Device Master File.⁹
• Formlabs BioMed Flex 80A Resin: For applications needing long-term skin contact (>30 days) or short-term mucosal membrane contact (<24 hours), ISO 10993 and USP Class VI certified.⁹
• Formlabs BioMed Elastic 50A Resin: Similar contact profile to BioMed Flex 80A, ISO 10993 and USP Class VI certified.⁹
• Regulatory Nuances:
  EU Class IIa devices require a Notified Body conformity assessment.1 Most FDA Class II devices need a 510(k) premarket notification.6 The availability of resins with well-documented biocompatibility for specific contact types (e.g., “short-term mucosal membrane contact”) helps streamline your material selection.9

Resins for Higher-Risk Dental Applications (Class IIb/III Considerations)

While most common 3D printed dental applications fall into Class I or IIa, some advanced or longer-term implantable devices might edge into Class IIb (EU MDR) or higher-risk FDA Class II/III categories.

• Potential Dental Device Examples:

• Long-term implantable components (though many are still traditionally milled PEEK or titanium).
• Certain patient-specific instruments intended for prolonged or critical tissue contact.⁹

• Resin Characteristics & Biocompatibility:
  These face very stringent requirements, including potential tests for chronic toxicity (ISO 10993-11), genotoxicity (ISO 10993-3), implantation effects (ISO 10993-6), and possibly carcinogenicity. Extensive chemical characterization (ISO 10993-18) and E&L studies (ISO 10993-17) are vital. Biostability (resistance to degradation in the body) is key.
• Resin Examples:

• 3Dresyns Biocompatible Resins: This supplier states their resins can be formulated for Class I, IIa, IIb, and even Class III devices, complying with ISO 13485 and ISO 10993.¹⁶ However, such claims always require rigorous device-specific validation by you, the dental device manufacturer.
• Formlabs BioMed Durable Resin: Specified for short-term tissue, bone, and dentin contact (<24 hours) and USP Class VI certified.⁹ Its use in “patient-specific instruments” could, depending on the surgical context, touch on higher risk considerations.

It’s the combination of contact duration and invasiveness that determines risk. A short-contact but highly invasive device could be higher risk than a long-contact skin device.⁴

Critical Factors Every Dentist Must Know When Using 3D Printing Resins

Understanding classifications is just the start. To truly ensure safety and efficacy in your dental practice when using 3D printed resins, consider these critical points:

1. Your Responsibility: The Device, Not Just the Resin

It’s a crucial distinction: regulatory bodies classify and approve the final medical device you create, not just the resin you bought.⁵ Even if a resin is marketed as “biocompatible” or “Class IIa compliant,” you, as the manufacturer of the dental device (be it a surgical guide, splint, or temporary crown), bear the ultimate responsibility for ensuring its overall safety and performance for the intended dental application.⁵ This includes validating that the resin, as processed by your specific workflow, is suitable.

2. The Impact of Your Workflow: Printing, Washing, and Curing

The journey from liquid resin to a finished dental part involves several steps, each potentially impacting biocompatibility and mechanical properties.⁵ This is especially true for in-office 3D printing.

• Printing Parameters: Settings like layer thickness and UV exposure can affect polymerization and final properties.
• Washing: This step, typically with isopropyl alcohol (IPA) or ethanol, is critical to remove unreacted resin. Insufficient washing can leave cytotoxic residues. Over-washing or using aggressive solvents can degrade the material or reduce strength.¹⁷
• Post-Curing: Essential for photopolymer resins to achieve complete polymerization, minimize residual monomers (which can be irritants or sensitizers), and attain optimal mechanical strength and biocompatibility.⁵ Under-curing is a significant risk.

The biocompatibility certificate from a resin supplier is often based on parts printed and processed under their specific, validated conditions. You must ensure your in-office or lab processes (printer, wash station, cure unit, settings, solvent quality, cure times/temperatures) are validated to produce an equally safe and effective part.

3. Sterilization: Keeping it Safe and Compatible

Many 3D printed dental devices, like surgical guides or instruments, must be sterile. The resin you choose must be compatible with your chosen sterilization method, and its biocompatibility must be confirmed after sterilization.

• Common Sterilization Methods for Resins:

• Steam Autoclaving: Cost-effective, but high heat can deform resins with low heat deflection temperatures (HDT) or cause moisture issues.¹⁷
• Ethylene Oxide (EtO) Gas: Effective for heat-sensitive materials, but EtO is toxic, requiring thorough aeration. It can also react with some materials.¹⁴
• Gamma Irradiation or E-beam: Can alter polymer chains, affecting mechanical properties or color.¹⁴
• Low-Temperature Hydrogen Peroxide Gas Plasma: Suitable for some heat-sensitive materials.¹⁷

Sterilization can induce physical and chemical changes in resins, potentially affecting integrity or biocompatibility.¹⁷ Always verify that your chosen resin is compatible with your sterilization protocol and that biocompatibility is maintained post-sterilization. Some resin manufacturers provide data on sterilization compatibility.¹⁴

4. Working with Suppliers: Documentation and Collaboration are Key

Choose reputable resin suppliers who understand the medical/dental field. They should provide:

• ISO 13485 Certification: Shows they manufacture under a quality management system for medical devices.⁹
• Detailed Technical Data Sheets (TDS): Listing physical, mechanical, and thermal properties.
• Biocompatibility Testing Information: Clearly stating which ISO 10993 parts the resin (or articles made from it under specific conditions) has passed, and USP Class VI results if applicable.
• FDA Device Master Files (DMF) or Manufacturer Access Files (MAF): Confidential submissions to regulatory bodies with detailed material information. You can reference these in your own submissions (with supplier authorization), streamlining the process.⁹
• Change Notification Policies: Reliable suppliers will inform you of any formulation or manufacturing changes that could impact the resin.
• Instructions for Use (IFU): Detailed guidance on correct processing parameters (printing, washing, curing) to achieve the stated properties and biocompatibility.

Resin manufacturers should also assist dental device makers in navigating testing and certification.⁵

5. Understanding Raw Material Scrutiny

Regulatory bodies expect that critical raw materials like resins are well-characterized.¹⁰ This includes understanding impurities, residual solvents/monomers, mechanical properties, and chemical composition.¹⁰ For photopolymer resins, assessing extractables and leachables (as per ISO 10993-17 and -18) is particularly vital.⁵ This detailed understanding of the resin itself forms the basis for its safe use in your dental applications.

Conclusion: Embracing Dental Innovation with Confidence and Care

The integration of 3D printing into dentistry offers incredible opportunities to enhance patient care, improve efficiency, and customize treatments. However, the power of this technology comes with the profound responsibility of ensuring every material and device used is safe, effective, and compliant.

As a dental professional, navigating the classifications (Class I, IIa, IIb, etc.), understanding the nuances of biocompatibility standards like ISO 10993 and USP Class VI, and recognizing the critical impact of your own manufacturing and sterilization processes are paramount. It’s not just about choosing a resin with a “biocompatible” label; it’s about a holistic approach that considers the entire lifecycle of the dental device, from resin selection to final patient application.

By prioritizing thorough material evaluation, validating your in-office or lab workflows, fostering strong relationships with knowledgeable suppliers, and staying informed about the evolving regulatory landscape ¹, you can confidently embrace the innovations of 3D printing. This diligence will not only protect your patients but also safeguard your practice in an increasingly sophisticated technological and regulatory environment. The future of dentistry is exciting, and with careful attention to these principles, you can be at the forefront, delivering cutting-edge care with the utmost safety and integrity.

Works cited

Sterilization of 3D printed resins – 3Dresyns, accessed May 14, 2025, https://www.3dresyns.com/pages/sterilization-of-3d-printed-resins

Medical device classification – European Union, accessed May 14, 2025, https://webgate.ec.europa.eu/udi-helpdesk/en/other-relevant-information/medical-device-classification.html

EU MDR Medical Device Classification: Classes and Examples – SimplerQMS, accessed May 14, 2025, https://simplerqms.com/eu-mdr-medical-device-classification/

Medical Devices | Definition, categories and classification – Eurofins, accessed May 14, 2025, https://www.eurofins.com/consumer-product-testing/industries/medical-devices/what-is-a-medical-device/

Deciphering Medical Device Risk Classification Under EU MDR – Artixio Consulting, accessed May 14, 2025, https://www.artixio.com/post/deciphering-medical-device-risk-classification-under-eu-mdr

Testing of biocompatible 3D printed resins – 3Dresyns, accessed May 14, 2025, https://www.3dresyns.com/pages/testing-of-biocompatible-3d-printed-resins

Overview of Medical Device Classification and Reclassification | FDA, accessed May 14, 2025, https://www.fda.gov/about-fda/cdrh-transparency/overview-medical-device-classification-and-reclassification

ISO 10993 vs USP Class VI: Medical Molding – The Rubber Group, accessed May 14, 2025, https://rubber-group.com/iso-10993-vs-usp-class-vi-medical-molding/

3D Print with Biocompatible Materials | All3DP Pro, accessed May 14, 2025, https://all3dp.com/1/3d-print-with-biocompatible-materials/

Powders and Resins for 3D Printing | Formlabs, accessed May 14, 2025, https://formlabs.com/materials/medical/

Medical Device Packaging Requirements You Should Know – Plastic Ingenuity, accessed May 14, 2025, https://www.plasticingenuity.com/blog/uncovering-medical-device-packaging-requirements/

www.qualio.com, accessed May 14, 2025, https://www.qualio.com/blog/fda-medical-device-classes-differences#:~:text=FDA%20medical%20device%20classification,-How%20many%20medical&text=Any%20medical%20device%20approved%20by,potential%20impact%20on%20patient%20health.

HIGH-PERFORMANCE MATERIALS FOR HEALTHCARE APPLICATIONS – Covestro Solution Center, accessed May 14, 2025, https://solutions.covestro.com/-/media/covestro/solution-center/story/brochures/covestro_ep_healthcare_reference_guide_final.pdf?rev=d3f1379e4ed141f6b17e88ddb36f7d38&hash=63907B241CC6719FBD7A68AC2CEA4821

Formlabs BioMed Flex 80A Resin – Dynamism, accessed May 14, 2025, https://www.dynamism.com/formlabs/formlabs-biomed-flex-80a-resin.html

Medical, accessed May 14, 2025, https://www.additive3d.com.au/wp-content/uploads/2024/01/FL-Medical-Resins.pdf

Formlabs BioMed Flex 80A Resin Cartridge, 1L – Source Graphics, accessed May 14, 2025, https://sourcegraphics.com/product/formlabs-biomed-flex-80a-resin/

Biocompatible 3D resins for medical devices – 3Dresyns, accessed May 14, 2025, https://www.3dresyns.com/pages/bio-compatible-3dresyns