Compliant or certified 3D resins or certified medical devices?

Photocurable 3D resins are increasingly used to manufacture medical, dental and orthodontic devices by stereolithography (SLA/DLP/LCD) and inkjet-based photopolymer printing. In parallel, some materials have been marketed over the years using ambiguous language such as “certified resin”, sometimes creating the impression that the resin itself is equivalent to a certified medical device.

Key clarification: regulatory conformity and certification apply to the finished medical device and its validated manufacturing process (including the production environment and quality controls). Liquid photopolymer resins are raw materials that must be compliant and suitable for the intended use, but they do not, by themselves, define the safety or certification status of the final device.

"Certifications must be obtained for 3D printed medical devices, which include the facilities and production system, by manufacturers of medical devices. 3D resins need to be compliant but not certified since certification applies to medical devices, not to their raw materials" by 3Dresyns

When raw-material certification can help (and when it cannot)

Case A: materials that do not chemically change during manufacturing

In some manufacturing routes, the raw material does not undergo relevant chemical transformation during production of the final device. In these cases, documented material compliance can help the device manufacturer’s conformity work. Typical examples include:

milling of metal implants,
milling of pre-polymerized plastic discs for dentures, crowns and bridges,
other subtractive shaping processes where the material chemistry remains essentially unchanged.

Case B: photoreactive resins that chemically transform during manufacturing

Photopolymer 3D printing is fundamentally different. Photoreactive resins chemically transform when they polymerize (liquid → solid). The degree of cure and the resulting level of residual monomers, extractables and leachables depend strongly on the full workflow. For this reason, presenting a liquid resin as if it were a certified finished medical device can be misleading if it encourages users to skip device-level validation and facility/process certification.

Why the workflow determines safety

The degree of curing and final safety of a printed medical/dental/orthodontic part depend on many variables, including:

Resin system variables: formulation design and version, pigment/additives, viscosity, and tuning to the printer.
Printer variables: wavelength, light power, optical uniformity, resin temperature control, printer design and maintenance state.
Geometry variables: part size, wall thickness, internal channels, build orientation, layer thickness and support strategy.
Cleaning variables: cleaning chemistry (solvent type and composition), cleaning time, cleaning temperature, agitation method, contamination control, and removal efficiency of residual monomers/contaminants.
Post-curing variables: post-curing unit wavelength and power, exposure time, temperature, atmosphere (air vs inert), immersion vs air curing, and part positioning.
Final cleansing variables: solvent type, method, temperature and time.

Because these variables are process-dependent and user-dependent, resin-level claims cannot replace device-level validation. The relevant conformity assessment applies to the manufacturing process and its final result: the finished medical/dental/orthodontic device.

Evidence: “biocompatible resin” does not automatically mean “biocompatible device”

There are many publications showing that photopolymer prints marketed as “biocompatible” (or assumed to be safe) can still produce toxic responses if printing and post-processing are not fully controlled and validated. Examples:

These findings highlight why accountability must remain with the device manufacturer and why the focus must be on certifying/validating finished devices and processes, not “certifying” raw photoreactive liquids as if they were finished devices.

Conclusions

3D printed medical devices fall within the scope of specific EU product legislation, such as the EU Medical Device Regulation MDR 2017/745. Therefore, manufacturers of medical devices must ensure that their 3D printed products meet the requirements of the applicable EU legislation, carry out the necessary conformity assessment procedures, compose a technical file, draft the EU declaration of conformity and affix the CE marking, before placing them on the EU market.

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