UBC Reports | Vol. 48 | No. 5 | Mar. 7, 2002

Researcher searches nature for better human implants

Shells, teeth may hold clues for hip, joint replacements

From heart valves to teeth, replacing faulty body parts with artificial implants is becoming increasingly common. In Canada alone, there are now 37,000 hip and knee joint replacements performed annually.

The problem is that many of the clinically engineered materials -- called biomaterials -- used to replace or repair living tissues have a limited lifespan and will need to be replaced eventually. It's a costly and painful prospect that UBC researcher Rizhi Wang says we can avoid by designing biomaterials that will last longer and function better in our bodies. And he says we need only look to nature for some engineering inspiration.

"You can always find some model in nature that is very close to what you are working on and in this you can find ideas and tricks to use in design solutions," says Wang, an assistant professor in the Dept. of Metals and Materials Engineering.

He calls his field of research "bio-inspired materials design and processing" because, he explains, he isn't trying to duplicate materials found in nature. He is looking for good examples of natural design interfaces that he can incorporate into the design of materials processed in the lab like plastic, polymer and titanium.

Wang's research focus is strengthening the gap, or interface, between an implant and the bone surrounding it with the goal of encouraging tissues to regenerate. Currently, most implants are made of titanium with a polymer cement or ceramic coating that may disintegrate in the body, causing the implant to loosen.

In his search for more bone-friendly materials, Wang has studied the teeth of horses, cows, alligators and even sea urchins, to examine their different surface structures and how effectively these act as an interface. He's also explored the pearl oyster's ability to produce a strong protective nacreous layer, the material responsible for creating a lustrous pearl.

Shiny, brittle human teeth have also yielded up some valuable lessons for Wang. He discovered that although a tooth's surface is covered in cracks, it is still able to function because of a thin, soft area between the tooth's hard, outer shell of enamel and inner core of dentin. Called the enamel/dentin junction, it performs much like a bumper for cracks.

In addition to continuing his studies on the interfaces found in mammal and human teeth and other biological systems, Wang hopes to gain a better understanding of how and why bones and teeth become deformed or fracture by examining them on a nanoscale. He will also conduct research on how surface patterns can help improve the fit between biomaterials and bone and teeth.