Ceramic Microscaffolding Process May Improve Jaw Reconstruction

Originally Published MDDI September/October 2003

R&D DIGEST

Scientists from the University of Illinois (UI; Champaign-Urbana, IL) and Sandia National Laboratories (Albuquerque, NM) have collaborated to create a ceramic prosthesis that can simplify jaw reconstruction procedures and improve patient outcomes.

The device was used recently during a reconstruction procedure conducted at Carle Hospital in Urbana. The device was fitted into the mouth of an elderly patient who had lost most of her teeth and a portion of her jaw. The fitting was intended to determine whether the implant, created at Sandia, had been accurately designed. Because scientists have performed only lab studies of the device's strength and permeability, however, the woman then had to endure the standard method of bone replacement, which involves transplanting bone from the pelvis.

If approved by FDA for in vivo testing, the scaffoldlike structure, made of layered mesh that is stronger than bone but porous, could be used to replace a portion of the mandible. The material would be gradually replaced by healthy, newly grown bone and blood vessels. The researchers believe that the ceramic scaffolding could reduce patient trauma and chances of infection.

The device is built mainly of hydroxyapatite, a material already approved by FDA for bodily implants, so approval of the new device is expected to be rapid.

"Surgeons and patients would love to eliminate both the bone retrieval and implant preparation processes," says Sandia scientist Joe Cesarano, whose team fashioned the new implant. "This test showed we can make artificial porous implants prior to surgery that will fit perfectly into the damaged region. The reconstructive procedure would then only require attaching the implant and closing the wound."

Autologous bone is used now to minimize rejection by the body. Harvesting bone, however, poses problems, says surgeon Michael Goldwasser, who performed the Carle Hospital procedure. Not only is a new area of patient discomfort created but the operation is time-consuming and requires anesthetics. These raise the risks of complications during the operation and in healing. "We could use cadaver bones," he says, "but then we face risks of rejection by the host and of possible transfer of disease."The body may also dispose of the foreign bone prematurely by absorbing it.

"What we want," Goldwasser says, "is a method by which I can see a patient in Illinois, then transmit x-ray information to someone who can make a part that would have the porous properties that would allow bone to grow into it, yet be strong enough for normal function." He learned of a process system at Sandia that could do the job.

The Sandia-patented process, called Robocasting, was developed to fabricate defense components out of ceramics in a way no ordinary mold or machining procedure could achieve. Situated on a truck, the system can make replacement parts on a battlefield, eliminating the need to carry millions of parts onto a site. Another goal of the Robocasting project, led by Cesarano, is to develop a way to form advanced catalyst supports that operate like a maze (rather than straight channels) to maximize chemical reactivity.

To cast a part, a computer-controlled machine dispenses liquefied ceramic paste—much like toothpaste squeezed from a tube—to form shapes of varying complexity along a prearranged path. To create the simulated bone scaffolding, the machine dispenses a hydroxyapatite mixture arranged in cross-laid slivers, each about as thick and as far apart as the diameters of ten human hairs.

"Bone, blood vessels, and collagen love to grow into a structure with pores of that size [500 µm]," says Cesarano. "The material becomes a hard-tissue scaffold for promoting new bone growth."

One challenge the researchers faced in developing the process was that although a CAT scan could accurately delineate the shape of a diseased existing bone, it could not show what wasn't there: the exact dimensions of what the bone would have looked like, were it healthy. This required the potentially expensive presence of the surgeon Goldwasser working with the computer programmers to create the dimensions of what should have been there but actually wasn't.

"Eventually, if it could be done electronically, it may be a very simple thing and cost-effective," Goldwasser says. Cesarano adds, "There is nothing inherently expensive about either the materials or the process."

Using a CAD/CAM method where a surgeon need only sketch the shape needed, a piece might quickly and inexpensively take shape at a remote site. "We'll see if the clinician, the bioresearcher, and the engineer can come up with a method to implement it," says Goldwasser.

Photos courtesy of RANDY MONTOYA/SANDIA NATIONAL LABORATORIES

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