3D Printing for Regeneration of Skeletal Defects

The ability to produce exact replacement parts for the skeleton has been a reality since the development of 3D printing. However, the ability to produce exact replacement parts that regenerate into normal functional tissue has been a goal of academic and industrial research for many years with no products achieving the goal to date. Our team at SteinerBio has been in pursuit of this goal for many years and we are pleased to announce a major breakthrough. Before we do that, however, we will first walk you through what needs to be accomplished to achieve the goal of 3D printing of science-based bone grafts to regenerate skeletal defects.

The most highly biocompatible, osteoconductive, and resorbable material known to science is pure phase crystalline beta tricalcium phosphate.

Because of those characteristics, it is currently the most studied bone regenerative material. While beta tricalcium phosphate (βTCP) is the best bone regeneration matrix, it still requires something to be added that stimulates bone formation. In our case, that is provided by the addition of our SteinerBio putty.

The biggest obstacle of printing βTCP is that it will not print with any known binders. Therefore, if your goal is a βTCP structure, you must first find a powder that will print, and then after printing, convert it into βTCP. There are many ways to produce βTCP, but most all require additives which make printing possible. However, the result is not pure beta tricalcium phosphate.

At SteinerBio, we decided that the powder used for printing must contain only the atoms that compose βTCP. Therefore, we could only start with the ions: calcium, phosphate, and oxygen. Now we needed to conceive of a compound that could be created that would produce a powder that could be printed and later converted into βTCP. Once we settled on the powder composition, we needed to calculate the exact molar ratios of the various molecules we were combining to produce the exact ratio of calcium, phosphate, and oxygen ions to form the precise crystalline structure.

To convert the molecules into the crystalline structure, intense heat is required for the ions to scramble into the desired structure. In addition, the various molecules must be in immediate contact with each other with the proper ratio for the scrambling to occur correctly. This is achieved with what is called a turbula. This is a scientifically designed machine that is used to mix molecules of different densities and spread them all out equally through the powder.

This is a turbula at work. Compounds of different densities are now spread throughout the powder in equal distribution.
Once all compounds are evenly mixed, the compounds need to be broken down and brought to the proper environmental conditions so they can reform into the desired structure. This is accomplished with intense heat. Exact time, temperature, ramping, and cooling are needed to achieve the desired result.

Once fired, the material must be cooled in a precise progression to achieve the final crystal structure. At this point, we have gone from a powder consisting of different molecules to a liquid, to a solid crystal, and it then needs to be ground to return it to a powder that can be printed.

The printing process applies a liquid to a powder which then sets. There are no printers designed to print TCP, so you purchase a printer that prints calcium sulfate, using water as a binder. In its manufactured form, the printer is useless for printing other materials. So not only are you using a different powder, but you must also use a different liquid that will react with your newly created powder. In the end, the printer must be completely modified for its new purpose for which there is no guidebook.

With the proper powder created, a binder now needs to be developed that will react with the powder and print it into a structure that can be handled. After printing, the printed structure needs to be converted into βTCP. Again, sintering is used to convert the printed structure into pure βTCP.

Early clinical tests showed promise, but we did not feel it was where we wanted to be for performance. Therefore, a few years ago we decided to start over. We learned that if we wanted the best βTCP on the market irrespective of how it was made, we needed to start with the perfect powder that would go into the printer for printing. About 6 months ago, we achieved that goal with a 100% pure composition in a highly crystalline structure which would combine with our binder to produce the best possible printed structure. After printing, we then needed to convert that structure into the purest, most crystalline βTCP possible. This month we achieved that goal.

Below is an XRD of our finished printed structure. X-ray powder diffraction (XRD) is an analytical technique used to identify the composition and phase identification of a crystalline material:

This XRD shows a 100% beta tricalcium phosphate. Each spike is βTCP and the sharpness of the spikes indicate the material is highly crystalline. There is no background noise noted. This XRD indicates our final product is composed of the purest most crystalline βTCP we have seen. We know this will perform to the highest standard and this is now under clinical testing.

We have resolved the regulatory requirements to bring this product to market and from previous experience we have worked out the logistics of making this technology available to your patients. The protocol is for your office provide a CT scan of your patient with a model of the dentition. Once the CT scan is loaded onto our computers, we will locate the position and size of the implants for your approval. Upon your approval, we will design the 3D graft around the implants. When the graft design is approved, we will print the βTCP grafts. The next step is to connect the graft design to the occlusal surfaces and print a surgical guide in resin. You will receive a surgical guide for implant placement. Once the implants are in place, you will cover the implants with putty, fill the 3D βTCP graft with putty, and place it over the implants. The grafts are designed to be covered with a d-PTFE membrane and then the tissues closed. Like our early implant protocol for single tooth replacement, the bone will grow into the graft and integrate to the implant. Cases will vary but loading is planned for 4 months after grafting. We will keep you posted on our progress and plan to have this technology ready for you in 3 to 6 months.


American Society for Bone and Mineral Research (ASBMR)

Tissue Engineering and Regenerative Medicine International Society (TERMIS)