Sunnybrook Magazine - Spring 2018

How facial prosthetics are made using 3-D printing

Silicon prosthetic ear

Here’s the step-by-step process that Sunnybrook has developed for building a craniofacial prosthetic with 3-D printing.

Meet the newest member of the team in the Craniofacial Prosthetics Unit (CPU). It chugs through the long, dark hours of the overnight shift. And it doesn’t take any breaks.

This team member is a 3-D printer, brought in to help Sunnybrook’s craniofacial team save time and eventually reach more patients. “The new printer takes away the four or five hours it would take us to sculpt an ear in wax,” explains anaplastologist Ann McLaren. “We are so keen to learn and use this new technology. It is the future.”

Used worldwide to make everything, from trinkets and cup holders to medical devices and cars, 3-D printers generate solid three-dimensional objects from a digital file through a layer-by-layer printing process.

At the CPU, McLaren and her colleague David Morrison create prosthetics for people who do not have an eye, ear or nose due to illness, injury or birth defect. It’s a long process with many steps as well as a lot  of artistry.

The recent addition of this 3-D printer to their team is streamlining their workflow. McLaren, a figurative sculptor and former makeup effects artist for the film industry, explains how the CPU team uses the 3-D printer in the process of making prosthetic ears.

First step in process of making prosthetic ears

1. First, an impression is taken of the patient’s existing ear (if the patient has one). Then, using a scanner, the team scans that impression into a computer. The 3-D printer is ideal for making prosthetic ears because it allows McLaren and her colleagues to easily take impressions and scan patients’ ears. For nose and eye prosthetics, however, McLaren notes that the team still uses sculpting techniques.

Image of the scanned ear is reversed

2.On the computer, the image of the scanned ear is reversed and turned into a mirror image. If needed, adjustments and slight corrections are made to the shape and size of the prosthetic.

Prosthetic ear being lowered into a tray containing a fine layer of liquid resin, which is hardened by a laser

3. The file is then downloaded to the CPU’s SLA (stereolithography) 3-D printer. The printer’s build platform lowers into a tray containing a fine layer of liquid resin, which is hardened by a laser. Lowered again, the platform exposes more liquid resin for the laser to harden. Repeated multiple times, this procedure creates a finished printed ear. The 3-D printer allows McLaren and her colleagues to make the prosthetic an exact match in size and shape to the existing ear. If there is no existing ear, the team will either sculpt it from previous photos or scan and print a family member’s ear, if available.
Before the CPU had the 3-D printer, the team would hand-sculpt a reverse ear in order to create a mold.

3D printed prosthetic ear

4. Usually, the 3-D printer does its magic overnight. “In the morning, we come in and the ear is waiting for us,” McLaren says. “We clean it up and cure it in a UV [ultraviolet] light box.” But it isn’t the prosthetic yet, she notes, because the material is too hard and inflexible.

Wax copy of prosthetic ear

5.McLaren and her team make a rubber mold of the printed ear and fill it with wax, producing a wax copy of the ear. Wax is used because it lets them modify the ear to fit onto the patient’s face. Depending on the patient’s needs, the wax ear prototype is contoured and trimmed to suit where the prosthetic will be located. During the sculpting process, care is taken to achieve a fine skin texture, as well as wrinkles, so the final prosthetic will blend in with the patient’s skin. Once those adjustments are made, the final mold is created.

Prosthetic hardware for surgical implants

6.If the prosthetic is going to be surgically implanted, McLaren says the CPU team then works with Dr. Ezster Somogyi-Ganss, a maxillofacial prosthodontist, to plan and place the hardware (shown above) for the prosthetic.

Silicone prosthetic ear

7. Next, the team creates the silicone prosthetic ear. Every prosthesis must be custom-colour-matched to the patient’s skin tone, McLaren points out. Once the colour tone is determined, the silicone is layered into the mold, then baked in a laboratory oven. The patient then comes in for a final fitting, which is when skill and artistry are important.

“We double-check that the prosthetic will sit flush to the face. We match the skin colour and add texture through freckles, capillaries and veins,” McLaren explains. “That’s when the prosthetic really comes to life. At the end of the process, if the patient is happy, I’m happy.”

Prosthetics help restore patients’ self-confidence. Some of McLaren’s patients have told her that, before they got prosthetic ears, for years, they wouldn’t get their hair cut, so the hair would conceal the missing ear. Or they’d always wear hats.

“[Now] they are excited they can wear their hair tied back, or wear an earring, or go [somewhere] and not have people stare,” McLaren says.
“We are delighted to have the 3-D printer as part of our team. It’s changing lives.”

» Read more about craniofacial prosthetics and facial reconstruction

All photography by Kevin Van Paassen

About the author

Alexis Dobranowski

Alexis Dobranowski is a Communications Advisor at Sunnybrook.