Process of 3D Printing Medical Devices
There are multiple steps to printing a 3D device. The number of steps for each device is dependent on many factors, including the complexity of the device.
The following sequence of steps is one example of the process:
- Device Design: A design is created and validated using digital models with pre-specified sizes or digital models matched to a patient’s anatomy.
- Software Workflow: The digital device design is converted to a buildable file that is sent to the printer. This file will often divide the design into layers, include additional support material to aid printing, and tell the printer where to build the device on the printer platform to prepare it for printing. The 3D printer often also requires some preparation to build different designs by changing settings for the material, type of design, and intended use.
- Material Controls: Like any manufacturing process, 3D printing needs high quality materials that meet consistent specifications to build consistent high quality devices. To ensure this, procedures, requirements, and agreements called material controls, which must be checked for every batch of material, are established between the suppliers, purchasers, and end-users of the material.
- Printing: The object is printed using the design specifications included in the file.
- Post-Processing: After printing is complete, one or more post-processing steps may be performed on the device or component. These may include cleaning to remove residual debris, controlled cooling (also called annealing), and/or additional steps such as drilling, cutting, polishing, and sterilization.
- Process Validation and Verification: Some device or component characteristics can be checked individually after they are produced to make sure they will function properly and meet specifications. This is especially true of geometric features which can be checked quickly and nondestructively. When other functional features, such as mechanical strength, cannot be checked individually because the test could destroy the object or is impractical, manufacturers validate their processes prior to production. Process validation ensures that a manufacturing process will produce product that is within defined specifications, as long as specified processing parameters are monitored and controlled.
- Testing: Device testing methods and results are submitted to the FDA to show that the device meets regulatory requirements and is reasonably safe and effective for its intended use. Each device or type of device has its own set of tests that may be based on FDA Guidance documents, international standards, or internal process controls. Devices manufactured by 3D printing are generally subject to the same regulatory requirements as more traditionally manufactured medical devices.
This flowchart is a simple example of one possible 3D printing manufacturing process.
Materials used in 3D Printed Devices
The FDA typically clears or approves finished medical devices, not specific materials for general use in the manufacture of medical devices, including materials that may be used in the manufacture of 3D printed devices. For example, the FDA has approved spinal implants made from titanium alloy, but the FDA does not review or provide blanket approval for the use of titanium in medical devices. Materials used in formulating or constructing medical products are evaluated within the context of FDA’s evaluation of the safety and effectiveness of the medical product for its intended use.
More specifically, the FDA evaluates a material as part of the finished device and its intended use, and determines if the device’s intended use and technological characteristics (including the materials) are reasonably safe and effective or substantially equivalent to the safety and effectiveness of a legally marketed device. If so, FDA provides approval or clearance (respectively) to individual devices for specific intended uses. This does not provide clearance or approval for the manufacturer to use these same materials in other devices.
Devices containing new materials do not necessarily require the FDA’s more rigorous premarket review process, known as PMA review. In fact, devices with new materials may be cleared through the 510(k) premarket notification process provided that the new material does not raise different questions of safety or effectiveness, and the submission demonstrates that the new material is at least as safe and effective as those in an equivalent legally marketed device.
Materials Used in Printed Dental Devices
For dental devices, including those manufactured using 3D printing technology, the FDA clears some engineered materials for a specific intended use as a device. These specific materials are considered finished devices that are suitable for use by health care professionals and are patient-matched or fitted at the point of care. Examples include dental restorative and prosthetic devices such as direct filling resins, dental cements, denture resins, orthodontic retainers, night guards, crowns, bridges, inlays, and onlays. In clearing these devices, the FDA typically requires performance testing on the material in its finished form to demonstrate that the material has the appropriate physical and material properties for its intended use.
It is important to note that the FDA has cleared these device materials only for that specific intended use, such as “to fabricate a denture base,” or “to restore a structural defect in teeth.” The FDA does not clear materials for unlimited intended uses. Each engineered material is cleared to make a specific device, with specific physical properties, and for a specific indication for use. For example, a device material cleared for specific intended use as a “tooth shade resin material” is not automatically FDA-cleared to be used for any other purpose, such as for an “Endosseous dental implant abutment.”
In cases where a manufacturer would like to use the same material for a new intended use, the FDA would evaluate information provided by the manufacturer to demonstrate that the material has sufficient properties for the new intended use. If the new intended use falls under a different classification regulation, the manufacturer would be required to satisfy any regulatory requirements for that classification regulation.
For additional information about how the FDA regulates medical devices, see Overview of Medical Device Regulation.