Trends in 3D Printing of Customized Medical Devices


ADDITIVE MANUFACTURING

Customized Dental Drill Guides, Dental “Temporaries”, Hearing Aids and Tissue Engineering Scaffolds

3D printing technologies have opened up the capabilities for customization in a wide variety of applications in the medical field. Using bio-compatible and drug-contact materials, medical devices can be produced that are perfectly suited for a particular individual.

Another trend enabled by 3D printing is mass customization, in that multiple individualized items can be produced simultaneously, saving time and energy while improving manufacturing efficiency. Early adopters of 3D printing technology for the mass production of customized medical devices include dental laboratories and hearing aid manufacturers. In addition, pre- clinical research in materials science, neuro- imaging, toxicology, and a diversity of other disciplines is rapidly increasing, with 3D printing enabling the development of revolutionary ideas and methods.

Dental Laboratories

Dental laboratories have adopted 3D printing to increase production efficiency and precision in the manufacture of medical devices. The introduction of 3D printing to a digital workflow decreases lead time by speeding up the flow of patient diagnostic information between the dentist and the dental lab.

To begin the process, a dentist scans the patient’s mouth to quickly and comfortably obtain precision data for the dental laboratory. The data is analysed using dental software such as 3Shape CAMbridge or DWOS-RPM from Canadian dental CAD/CAM software supplier Dental Wings, based in Montreal, and a solution is developed for the patient. The laboratory can immediately and seamlessly use the data to begin production of the necessary components for the case. Multiple cases can be produced simultaneously, allowing laboratories to fulfill their customer requirements quickly and with consistent quality.

Advances in materials research have led to the availability of 3D printing options that are bio-compatible and certified for use directly within the mouth, for both short and long-term use. One such material is E-Shell 600 (trade named Clear Guide) for use on the EnvisionTEC Perfactory series of 3D printers. Clear Guide is certified by United States Pharmacopoeia (USP) Class VI testing for the production of drill guides on EnvisionTEC’s Perfactory mini desktop 3D printer.

The surgical drill guides are medical devices which allow for precise drilling into a patient’s mouth for the placement of dental implants. Each drill guide must be carefully planned for the individual case and bio-compatibility is essential, as it will remain in the patient’s mouth in contact with exposed tissue and nerves during the implant process. The spectral and light energy output of the Perfactory 3D printer is a critical component for ensuring bio-compatibility, thus linking both the machine and the material to the USP Class VI certification.

Dental temporaries represent another application area for bio-compatible 3D printed materials. The dental implant process requires significant healing time between the original surgical preparation and the final implant procedure. This healing process may take from several months to a year depending on the need for bone grafting to ensure the viability of the implant.

During this period of time, a temporary crown may be placed to preserve the gum architecture surrounding the implant location as well as to serve an aesthetic function. Due to the length of time the temporary crown will reside in the mouth, bio-compatibility as well as material stability is required. EnvisionTEC’s E-Dent material for use on the Perfactory line of 3D printers was the first CE (Conformité Européenne) Certified and 510(k) FDA-approved 3D printed material for the purpose of creating temporaries.

E-Dent comes in three commonly used dental shades (A1, A2, and A3). The structures can be cut back and then layered using any light-curable shade composite in order to match the existing surrounding teeth. 3D printing allows for the production of highly accurate temporaries in a matter of hours, saving both time and labor.

Hearing Aids

Hearing AidsThe hearing aid industry boasts perhaps the highest “installed base” of customized final consumer devices that were produced using 3D printers. The E-Shell line of liquid photo-reactive acrylates is both CE-certified and classified as Class IIa bio-compatible according to ISO 10993/Medical Product Law for Hearing Aids when used according to the published guidelines on an EnvisionTEC Perfactory 3D printer.

Available in over fifteen colors, including transparent and opaque options, the E-Shell line of materials are water and perspiration-resistant. This range of materials enables the hearing aid manufacturer to offer a custom patient solution in terms of both fit and skin coloration.

EnvisionTEC Perfactory and 3D- Bioplotter systems have been used since 2002 for a variety of medical applications. Most research done to date using our machines has been in the pre-clinical setting, yielding many publications (abstracts provided upon request) by pre-eminent scientists from the materials science, neuro- imaging, and toxicology disciplines. In the clinical setting, patient CT or MRI scans are used to create STL files to print solid 3D models which can then be used as templates for implants.

Tissue engineering and controlled drug release

Tissue engineering and controlled drug release applications require 3D scaffolds with well-defined external and internal structures. The 3D-Bioplotter from EnvisionTEC can fabricate scaffolds from a wide array of materials, from soft hydrogels over polymer melts to hard ceramics and metals. The technique may be described as the deposition of material in three dimensions using pressure.

Materials range from a viscous paste to a liquid, and are inserted using syringes moving in three dimensions. Air or mechanical pressure is applied to the syringe, which then deposits a strand of material for the length of movement and time the pressure is applied. Parallel strands are plotted in one layer. For the following layer, the direction of the strand is turned over the center of the object, creating a fine mesh with good mechanical properties and mathematically well-defined porosity.

By permitting the use of pastes, hydrogels, melts, and any other liquid which may be quickly solidified, this technology enables a wide range of 3D printing applications. The building platform may be a glass plate, a cooled metal surface or even a liquid, which not only allows for solidification through ionic transfer and other cross-linking methods, but also provides buoyancy support for plotted strands during the solidification process. By controlling the strand thickness, precise drug releasing properties are achieved. The strand thickness is also relevant when adding cells to the process itself, as the distance between the surface of the strand and the cell position is crucial to its proliferation. Finally, the design of the interior of the object will strongly affect its mechanical properties, which may be changed to mimic the type of tissue it is replacing or supporting.

Summary

In summary, there are a number of existing application areas for 3D printing that require specialized materials that meet rigid and stringent bio-compatibility standards. A range of materials for the hearing aid and dental industry already meet those requirements and are in the marketplace today under the brand name EnvisionTEC. Scientists from multiple disciplines conducting pre-clinical research are experimenting with their own proprietary or third party materials, using EnvisionTEC machines. Future 3D printing applications for the medical field will certainly emerge with the development of suitable additional materials for diagnostic and therapeutic use that meet CE and FDA guidelines.