Table of Contents
What is 3D Printing?
3D printing also known as Additive Manufacturing, is a process in which materials are deposited layer-by-layer to form a 3D object from a digital file. This digital file can also be designed using CAD software or obtained using 3D scanners. The digital file is exported in an STL format to the printer and the part is printed. Printing involves layering materials, like plastics, metals, or bio-materials to create objects in varied shapes, sizes, and colors.
3D Scanning
The process of converting an object into a digital file is called 3D scanning. With the help of a scanner or camera, any object can be scanned by capturing all contours and then converted into a digital file for further modifications like editing or designing a CAD component over the scanned model. Photogrammetry is one technique used in the 3D scanning of objects. It involves capturing multiple photos of an object and combining them to create a digital file using algorithms. Various 3D scanning tools and commercial scanners are available to cater to resolution requirements. Apps like 3D live scanner or Qlone are available and are compatible to be used with phones, tabs, and iPads.
Dental scanners are being used by many dentists to capture data from the patient without the hassle of molds and imprints. The model can be recaptured if not perfect and can be easily worked upon to build braces and aligners. Another application is scanning limbs to design customized orthosis.
3D Modeling and slicing
3D modeling can be done using CAD software like Solidworks, Fusion 360, and Blender which enable the designing of guides, implants, instruments, braces, and more medical parts either from scratch or over the scanned design files. Learners and tinkerers can download digital pre-designed files from open-source websites like Tinkercad and Thingiverse. These files can be modified and printed to the requirement.
Slicing is an important step between the 3D-designed model and printing. The designed model is split into slices and the parameters like layer thickness, infill, and supports are defined to print the part with proper strength in optimum time. The simulation model can also be viewed prior to printing. CURA, Slic3r, and Simplify3D are a few of the commonly used slicing software.
3D Printers
A variety of 3D printers are available today and depending on the type of material used, they can be classified into filament-based, resin-based, and metal printers. A few of the most commonly used printing technologies are the following:
- FDM- Fused Deposition Modeling
- SLA- Stereolithography
- DLP- Digital Light Processing
- SLS- Selective Laser Sintering
- SLM- Selective Laser Melting
- DMLS-Direct Metal Laser Sintering
Materials
A wide array of materials is available today which, depending on the requirement and application can be used with different 3D Printers. Especially in the medical industry, the material needs to be biocompatible and sterilizable and below are a few commonly used types.
- Thermoplastics: PLA, ABS, PC, PP, PE, PVC, TPU, PEEK, PVC, Nylon. Ideal for anatomical models, implants, and surgical instruments.
- Resins: Photopolymer resins are used to print models of soft organs, casting molds, and vasculature models.
- Ceramics: Bioceramics like Zirconia, Hydroxyapatite, and Calcium Phosphate is used for implant coating which enables bone integration
- Metals: Titanium alloys, stainless steel, and cobalt-chromium alloys. Ideal for Orthopaedic and CMF implants, spinal cages, and orbital plates.
Applications in Healthcare
Segmentation
Medical image segmentation is the extraction of 3D models from the DICOM data of patients’ CT/MRI scans. From the derived 3D model, the region of interest is chosen and the desired anatomy is isolated. Various tools such as thresholding, masking, rendering, and Boolean operations are used to segment and process the required data. Currently, there are few AI-based software like Materialise Mimics and Synopsys Simpleware which automatically segment -nearly 70-80% of the data from the selected region and also enable you to add required data and remove unwanted details.
Anatomical Models for pre-operative planning
3D printing is widely used to produce anatomical models. A 1:1 patient-matched anatomical model can be printed by segmenting the DICOM data. These models help the surgeon in pre-planning the surgery and also to do a mock-up beforehand to achieve better surgical outcomes. Pre-planning surgeries reduce OR time and enable faster post-op recovery. Especially in keyhole surgeries, these models when printed in advance help plan a better surgical approach. The models can be printed in different colors and materials to mimic the actual part.
These models are also helpful in educating the patients before getting their consent. They can be used as visual aids for presentations, and training medical professionals. Accurate and detailed reference models can also be used to pre-shape medical plates.
Medical Devices and Surgical Instruments
The recent Covid-19 pandemic has shown the world how much 3D printing can help in printing customized tools and essential devices in-house for emergency cases. Many Nasopharyngeal swabs, ventilator splitters, and PPE-face shields were printed to meet the shortage and long demand.
Certain medical devices like the Hearing aids which take days and sometimes weeks to be manufactured through conventional methods are now being 3D printed within a day that too matching the patient’s unique ear canal. Heart valves with a proper fit can also be 3D printed.
Customized tools are designed and iterated to match not only the patient’s anatomy but also enable proper gripping for the surgeons to help them in performing procedures with ease can be printed. Surgical instruments like forceps, clamps, hemostats, and retractors are commonly printed in biocompatible and serializable plastics and metals.
Orthotics and Prosthetics
Orthotics is one field that is extensively adopting this technology. With reference to age, body type, and gender, every patient has a different limb size and the pre-defined sizes available in the market do not provide a perfect fit for all. With the ease of customizing and printing in-house, the process has been simplified and better-fitting orthosis and insoles can be printed easily matching the patient’s measurements. The scan of the limb is taken and the AI-based software automatically designs and gives a perfectly fitted orthosis in modifiable patterns and colors.
Every year many people lose their limbs in accidents or due to medical complications. Commercially available prostheses are heavy, expensive, and do not possess a good fit. In such cases, 3D printing can be used to print customized prosthetic sockets in a short period and also offer a better grip. e-NABLE is one such organization that produces low-cost prosthetics and also open sources their designs making them accessible to people all around the world.
Implants and Surgical guides
Implants matching the patient’s anatomy can be designed using CAD tools and 3D printed in metals like titanium and stainless steel. The design flexibility helps in making the implants lighter, stronger, and also porous which enables osseointegration with the surrounding bone giving it a sturdier fit to the body part. This enhances implant performance by making it last longer. Orthopedic implants, plates, spinal cages, screws, and also dental implants can be custom-printed. The implants need to be properly post-processed and abide by the regulatory requirements before being implanted into the body.
Surgical guides aid in pre-planning and assisting with where the cuts are to be made and where the drilling for screws is to be done. These guides are printed in biocompatible and serializable materials and their usage helps in reducing errors thereby reducing complications and giving better surgery outcomes.
Dental
The dental industry is by far the most used application of 3D printing technology. The patient data from CBCT scans are extracted and customized parts such as dental crowns, CMF implants, abutments, screws, and mandible plates are accurately designed and printed. Printing this way is also a more cost-efficient option compared to traditional methods.
Intra-oral scanners can be used to scan and acquire a digital format of the teeth. With the help of processing software, Dental professionals can perform any needed modifications and print the teeth models. Over these models, perfect-fitting aligners are vacuum pressed. 3D printing has wide applications in dentistry. Dentures, drilling, surgical guides, and dental frameworks can also be precisely designed to match the patient’s anatomy and printed. In cases like Mandibular reconstruction, jaw models segmented from patients’ scans are printed to enable the pre-bending of plates before surgeries.
Conclusion
The above-mentioned applications are just a few of the many advantages this technology has to offer. Many healthcare institutions are establishing Point-of-Care (POC) labs to have this technology in-house instead of out-sourcing. This involves surgeons in design optimizations and also helps in reducing travel time and cost. This technology is even expanding into the Bioprinting and Pharmaceutical industries. Though this technology is gearing up to become part of the medical field, the challenges of reimbursements from insurance companies and the absence of a proper regulatory framework are impacting its adaptation.
Despite the limitations, this technology is evolving rapidly thereby, transforming healthcare and helping save more lives
