Additive Manufacturing Technologies in the Medical sector

Subject - 3D Printing

Introduction: -

The term three-dimensional (3D) printing was initially used to describe a process to deposit a binder material by inkjet printer heads, layer by layer, onto a powder bed. It was developed mainly as a rapid and cheaper alternative to the industrial prototyping process. It has become the first choice of industry for prototyping and is known as rapid prototyping (RP). Over the years, people have realized the immense potential of this technology and are being termed the third, fourth, and fifth industrial revolutions by various opinion-makers. The use of 3D printing technology in medicine is proliferating rapidly and is being extensively used in research, teaching, prosthetics, and orthotics for customized implants, pre-surgery 3D modeling, and tissue printing.

History: -

The first mention of 3D printing RP is as an application filed for a patent in 1980 in Japan by Dr. Kodama. He did not subsequently file the full patent specifications required and therefore was not given the patent. The first patent was given to Chuck Hull in 1986 for stereolithography apparatus (SLA). He is the co-founder of the 3D systems corporation. In 1989, Carl Deckard was issued a patent in the US for selective laser sintering (SLS) another RP process. Furthermore, in 1989, Scott Crump, a cofounder of Stratasys Inc., was issued a patent for fused deposition modeling (FDM) another technology for 3D printing. In fact, FDM has become the most popular technology in low-cost 3D printers, the world over.

Material Used: -

Ceramics

Paper

Wood

Glass

Metal

Food

Combinations

Biomaterial

Medical Applications of Additive Manufacturing

Medical applications of additive manufacturing can be classified in several ways but this article follows application classes-based classification. AM applications can be classified into the following classes: “models for preoperative planning, education, and training”, “inert implants”, “tools, instruments, and parts for medical devices”, “medical aids, supportive guides, splints and prostheses” and “biomanufacturing”. For a more general classification, this can be modified so that implants do not need to be inert, and models for preoperative planning, education, and training could also include postoperative and operative models using the term “medical models”. shows an example of an application in each category including an

(a) preoperative model of a skull and heart,

(b) craniomaxillofacial implants,

(d) personalized and mobilizing external support and

(e) a scaffold for zygomatic bone replacement and resorbable orbital implants.

(a) Medical models; (b) implants; (c) tools, instruments, and parts for medical devices; (d) medical aids, supportive guides, splints, and prostheses; (e) biomanufacturing.

Classification of medical applications of additive manufacturing:

Medical models;
Tools, instruments, and parts for medical devices;
Medical aids, supportive guides, splints, and prostheses;
Biomanufacturing.

Medical Models

Medical models are based on patient anatomy, and they can be used for pre-and postoperative operative planning and training; training medical students, and informing patients and patients’ families. The geometry can be transformed, for example, by taking only interesting sections or scaling them up or down. If models are used for training, such as bone drilling, the haptic response might be desirable to be close to the bone. Medical models are widely used in the craniomaxillofacial area, but there are also cases, for example, from different limbs and other bone structures such as the spine and pelvis. If these are utilized in the operating theater, it might be recommended that the models be sterilized, but usually, the material option can be quite freely selected which highlights also that these are one of the most common applications. a typical process workflow for manufacturing medical models starts from patient anatomy captured via medical imaging, such as computed tomography (CT), magnetic resonance imaging (MRI), or ultrasound, followed by constructing a 3D model geometry for AM using segmentation algorithms. After AM, there is often a need for post-processing such as removing the support structures.

Typical process flow for implants

Tools, Instruments, and Parts for Medical Devices

Tools, instruments, and parts for medical devices allow or enhance a clinical operation. They might utilize patient-specific dimensions and shapes, for example, in drilling guides, and can be invasive and need a sterilization process, since they can be in contact with body fluids, membranes, tissues, and organs for a limited time. This class includes surgical instruments and orthodontic appliances. One of the largest and most successful businesses in this class is using the VAT photopolymerization process to create molds for vacuum forming clear orthodontic aligners. When patient-specific dimensions are utilized, the process is similar to that of implants and preoperative models from medical imaging or 3D scanning. 3D modeling can be conducted by referring to the 3D model of the patient’s anatomy or from scratch if a patient-specific geometry or fitting is not needed. Post-processing might include support removal, heat treatments, machining, and sterilization. Tools, instruments, and parts for medical devices are typically made with the process flow shown in. For example, the process starts by taking an impression of the patient’s teeth, 3D scanning it, followed by 3D modeling, VAT photopolymerization AM, post-processing, and using the part made as a mold for soft orthodontic aligners.

Typical process flow for tools, instruments, and parts for medical devices.

Medical Aids, Supportive Guides, Splints, and Prostheses

In this class, parts made with additive manufacturing are external to the body, and these can be combined with standard appliances to allow customization. Long-term and postoperative supports, motion guides, fixators, external prostheses, prosthesis sockets, personalized splints, and orthopedic applications are examples of applications in this class. The process can start with medical imaging followed by segmentation, 3D scanning, or 3D measurements that can provide data directly for use in the 3D modeling phase. Alternative manufacturing methods for additive manufacturing are quite often computer numerical control (CNC) technologies. Parts may require different kinds of post-processing depending on the application such as support removal, heat treatments, and painting or coating. The typical process flow for medical aids, supportive guides, splints, and prostheses using AM is presented. The example case is a personalized and mobilizing external support for a pilon fracture, where 3D modeling is based on measuring the patient’s ankle movement and adjusting the additive manufacturing pieces to locate the hinge so that it controls the movement under force close to the free movement of the ankle.

The typical process flow for medical aids, supportive guides, splints, and prostheses

Biomanufacturing

Biomanufacturing is a combination of additive manufacturing and tissue engineering. Materials need to be biologically compatible and often active with the body so many different polymers, ceramics, and composite materials are used. Porous structures with cultivation and a 3D matrix can affect cell specialization. The materials can be osteoinductive, osteoconductive, or resorbable. Shapes can be personalized to correspond to defects. For personalized shapes, the patient’s geometry needs to be captured using medical imaging or 3D scanning. In the 3D modeling phase, micro-and macrostructures are modeled, and porous structures are often used for attracting cells and cell growth. The process often needs to be sterile or parts made with the ability to be sterilized after printing. Before final application, there might also be the need for cell growth in vitro or in vivo. an example of an orbital floor resorbable implant stating patient geometry with CT and segmentation followed by 3D modeling and AM of the implant. After manufacturing, the implant is sterilized

Additive Manufacturing for Medicine and Healthcare

The use of additive manufacturing applications is on the rise, with the market value expected to increase from $6 billion in 2017 to nearly $26 billion by 2022.

The advantage of additive manufacturing comes from creating complex structures that vary in complexity, customization, lightweight, strength, and speed. As additive manufacturing for medical devices continues to gain momentum, there are five main areas where we are seeing the most growth opportunity from this evolving technology. Let’s take a look at how the capabilities of additive manufacturing have become the de facto method of production in these industries

Dentistry

The largest market for additive manufacturing in medicine right now is dentistry and related orthodontics such as bridges, crowns, braces, and dentures. Currently, digital dentistry is a $2.5 billion industry and this is set to more than double in a few years.

Digital dentistry is more of a workflow than a single technology. This process typically begins with a scannable model or impression that’s subsequently converted into 3D digital data.

Many 3D-printed dental appliances are easily customized for a precise fit while also being printable in a variety of substrates, from flexible polymers to rigid titanium.

Dentures from EnvisonTEC

There are also specialized printers configured to use the dental scanning software, along with biocompatible resins, that can fit in small offices and clinics for immediate, on-the-spot solutions ready in a single day.

Anatomical Models

The human body is complex and each is unique. Therefore, when doctors and clinicians need to consider individual treatments, it helps enormously to see an accurate model of the subject in question – whether that’s a bone, an organ, a tumor, or a limb

3D scanned and printed anatomical model for the study

Luckily, this is now a reality. Great strides have been made in medical imaging technology, including highly accurate full-color 3D scanning down to the vascular level. Using this data, along with sophisticated topological mapping software such as Materialise, biomedical engineers can use 3D printers to create realistic models for analysis.

From these models, doctors can then devise surgical strategies like where to make incisions. Also, models assembled from multiple pieces can be disassembled to reveal structures within that might otherwise have been blocked from a surgeon’s view. The number of hospitals in the United States with a centralized 3D printing facility has grown exponentially, from three in 2010 to more than 100 by 2019.

General Tools

This is a broad category of auxiliary equipment that would be expensive and time-consuming to develop in smaller volumes. It includes clamps or grips designed for an individual patient’s anatomy, possibly to aid in examinations, treatments, or surgical procedures.

3D printed parts from iLab/Haiti

Additive manufacturing applications are also being used in many developing countries to design non-specific clamps, catheters, and other fittings that are fast and economical to produce on the spot as needed.

Prosthetics and Orthotics

Additive manufacturing technology has helped expand patient options for prosthetics and orthotics in terms of fit, function, and aesthetics. A prosthetic can be a replacement of a body part, either internally (i.e., hip joint) or externally (i.e., a missing limb).

Taiwanese girl with 3D printed articulated prosthetic

Traditionally, prosthetic limbs were inadequate in their customization options. They were either limited in their functionality or incredibly expensive, requiring a lot of measurement, test fitting, and hand-craftsmanship that is inaccessible to many people. This is especially true in remote areas or regions experiencing military conflict, where such prosthetics are in high demand. Orthotics are also custom pieces, made to assist the wearer’s bone structure with extra support or by correcting misalignment issues. Using modern polymers, 3D printed plastic orthotics are strong, lightweight, durable, and also pliable for added comfort. They can also help mitigate foot pain caused by conditions such as diabetes, arthritis, or plantar fasciitis.

Health Monitoring and Drug Delivery

Another advantage of additive manufacturing for medical devices making make complex micro gadgets that work inside the body to deliver medicine to monitor a patient’s health.

MIT, in conjunction with Harvard’s Brigham and Women’s Hospital, has developed an ingestible device that can remain in the stomach for a month. Self-powered, it delivers discrete amounts of drugs for patients requiring long-term care, including those who require treatment for cancer or HIV. This device is currently in the testing stage, but it represents the kind of approach that many other researchers are trying to refine Such micro devices will soon be able to transmit data wirelessly to an external medical wearable for detailed health monitoring. Other printed sensors can be injected into the bloodstream to provide active monitoring of blood glucose levels, blood oxygenation, and other critical metrics that doctors will use to quickly respond to a patient’s medical condition

Advantages:

1. Flexible Design

2. Rapid Prototyping

3. Print on Demand

4. Strong and Lightweight Parts

5. Fast Design and Production

6. Minimising Waste

7. Cost-Effective

8. Ease of Access

9. Environmentally Friendly

10. Advanced Healthcare

Disadvantages:

1. Limited Materials

2. Restricted Build Size

3. Post Processing

4. Large Volumes

5. Part Structure

6. Reduction in Manufacturing Jobs

7. Design Inaccuracies

8. Copyright Issues

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Additive manufacturing Technologies in medical sector

Additive Manufacturing Technologies in Medical Sector