This New Material Will Be Used to Reconstruct People's Faces

Whether it's for 3D printers or hand moulded, the new polymer has the potential to be a game-changer for reconstructive surgeries of the future.

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Aug 20 2014, 12:00pm

3D printed polymer skull fragment.

The discovery of a new polymer composite suggests doctors have found the perfect material to redesign face bones with holes from trauma or disease.

A team of researchers from Texas A&M University have developed a biodegradable shape-memory polymer (SMP) that can both fill in the gaps in your face and serve as a framework for your own bone cells to swoop in and grow into. That means face bones might be able to re-grow themselves using the polymer as a shell.

The team, which presented its findings at 248th National Meeting & Exposition of the American Chemical Society in San Francisco earlier this month, created the SMP by chaining together molecules of polycaprolactone, or PCL for short, and then whipping it into a sort of foam.

PCL, which has been on the medical scene since the 70s, is being looked at for use in drug-delivery systems and vascular grafts. It's also used for 3D printing and modeling, which opens up the new SMP to even more potential—a different study earlier this year used a custom 3D printer to print "anatomically shaped" PCL bone scaffolds. And other polymers are already being used to print missing parts of people's skulls.

Imagine you're missing a chunk of bone in your face too big for your body to naturally repair—maybe you had a tumour removed from your jaw, you were in a terrible car accident, or were born with a cleft palate.

Whatever the reason, bones are important to the structural integrity of your face and your current options for filling in the gaps aren't the most promising.

At the moment, the most popular procedure is an autograft, where doctors grab bone tissue from somewhere else in your body and try to shape it to fit the missing piece. Alternatively, they can fill in missing fragments with cement or putty.

The first option can cause serious complications at the donor site, which results in multiple surgical intrusions the patient has to recover from. The second option is worse: cement can become brittle when it hardens and doesn't allow for bone to grow back, stifling cells from reaching the interior cement.

But the new polymer—a porous, sponge-like material that's soft and malleable at 60°C (140°F)—stiffens up without becoming brittle when cooled to body temperature.

And the pores it leaves behind during the cooling process are important—they provide more space for bone-producing cells called osteoblasts to come in and start rebuilding.

Opening up the new polymer to 3D printing bones, like skull fragments, is a logical extension for this new material. Companies like Oxford Performance Materials have already used forms of polymer to repair patients with missing bone fragments.

But while the polymer OPM used for a procedure in 2013 also provided space for bone cells to fuse with the polymer, this new SMP hybrid allows for greater integration of the polymer to the patients own cells. Researchers also coated the SMP with polydopamine, a substance that helps the material bind to the existing bone and also encourages the growth of osteoblasts.

A surgeon can simply heat up the polymer, pop it in place, and let the new material cool.

In a three-day-long test, researchers found that polymer samples seeded with human osteoblasts and coated with polydopamine grow five times more osteoblasts than a polymer without the coating.

"The work we've done in vitro is very encouraging," study leader Melissa Grunlan said in a statement. The team's next move is to test out the polymer on animals with bone defects in their heads, and hopefully, Grunlan said, move their way up to clinical trials.

Instead of invasive surgeries gathering autograft tissues, a surgeon can simply heat up the polymer, shape it so it perfectly fills out the defect (potentially with a 3D printer), pop it in place and let it cool down.

The patient's bone cells would then start growing within the pores of the polymer, and since it's biodegradable, the scaffold would gradually disappear, leaving behind the newly-formed bone. And the drawbacks, so far, are minimal: at worst, it can take three to four years before it completely biodegrades and leaves the newly-formed bone behind.

The discovery has the potential to be a game-changer for reconstructive surgeries of the future. No more cutting bone out from someone's hip and trying to chisel it into the shape of the missing piece, and no more plugging in gaps with cement. Instead, the rise of shape-memory polymer could help make 3D printed fragments the go-to procedure for patients looking to fill the holes in their bones.