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Process

Using the case of a 73 year old female who has experienced severe bilateral bone loss in the mandible, materials scientists, engineers, medical 3D artists, computer-aided designers, and the patient's attending physician created a workflow by which a synthetic ceramic scaffold was designed, and fabricated specifically for this patient. This workflow involved true collaboration between all parties involved, as the surgeon sought to transfer his intuitive knowledge of the precise structure of the implant to the 3D modelers at Beckman, who then in turn transferred their work to the fabricators of the implant at Sandia.

Credit: Imaging Technology Group, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign
Credit: Imaging Technology Group, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign

2D CT Scan Image Data (left) and Isolated Mandible (right) in Volumetric 3D Reconstruction

 

This process required ITG to extract the necessary 3D information from the 2D image slices of the CT scan. The surgeon then worked with with ITG in defining the boundaries for the implant and making accommodations for an existing nerve. ITG worked with CT technicians at Carle to ensure the accuracy of the CT data measurements and to establish that the extracted model was true to the original data.

Credit: Imaging Technology Group, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign
Credit: Imaging Technology Group, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign

Sketches by Sinn-Hanlon and Goldwasser defining the path of the inferior alveolar nerve (left) and the boundaries of the implant (right).

 

ITG then created a computer-generated 3D model whose bottom surface precisely fit the eroded mandibular surface that it would rest on. A canal was built into the ventral surface of the implant that was large enough to accommodate the exposed nerve, but would leave an adequate amount of contiguous surface on either side for jaw strength and the insertion of screws to anchor the implant into the mandible. The top surface of the implant was modeled with the intent of restoring the natural shape of the jaw and providing a surface that would support dentures. The two surfaces were welded together to complete the model for the implant.

Credit: Imaging Technology Group, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign
Credit: Imaging Technology Group, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign

The final precise-fit undersurface of the implant with nerve accommodating canal (left)
and the final model blended onto the new top surface of the implant (right).

 

Once the implant was created, the model was 'printed' use ITG's rapid prototyping machine so that the researchers could evaluate the fit of the implant with a physical model. Evaluation of these models concluded that the fit was very precise and well within the tolerances required. The 3D computer model was then e-mailed to Sandia, while physical prints of the jaw and implant for shipped for reference.

Credit: Imaging Technology Group, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign
Credit: Imaging Technology Group, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign

The final implant model (left) and a physical 'print' of the jaw and implant model (right).

 

Once received at Sandia, they proceeded to investigate methods for fabrication of the object using their patented process called 'robocasting'--a technology similar to the rapid prototyping machine used by ITG, but unique in its ability to work with various speciality materials. In this project, the device is used to create scaffolds of a substance primarily made up of hydroxyapatite--a substance chemically identical to those found in human bone. These scaffold structures, developed by Dr. Jamison, are unique in their ability to withstand the extreme forces that a bone implant would undergo.

The robocasting device is used to create a block of scaffolding material that can later be milled to a precise shape. The block is temporarily embedded in wax to provide strength to the object during the milling process.

Credit: Dr. Joseph Cesarano, Sandia National Laboratories

The milled implant from a wax-embedded scaffold of hydroxyapatite.

 

Once the device is milled, the wax is melted out, and the implant is finished. The porous structure of the scaffold allows bone to grow into it, providing the future basis for the growth of new bone in a patient.

Credit: Imaging Technology Group, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign

The final implant scaffold after the wax has been removed.

Credit: Imaging Technology Group, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign

The underside of the final implant scaffold, showing the modeled canal for the nerve path.

Credit: Dr. Joseph Cesarano, Sandia National Laboratories
Credit: Dr. Joseph Cesarano, Sandia National Laboratories

The final implant scaffold fit tested in the previously 'printed' jaw.
Exterior side (left), and interior side (right).

 

Finally, during the patients' previously scheduled autograft procedure, the implant was sterilized in an autoclave and inserted into place for fit testing. The surgeon proclaimed the implant to 'fit like a glove'.

Credit: Carle Clinic, Urbana, IL

The final implant scaffold fit tested in the patients jaw.




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