Our Stories 02 Advance into the Medical Product Field

Story 02Expanding the Technical Possibilities of Ceramics and Developing Artificial Bones for Medical Treatment.

Due to the aging of the population, the prevalence of bone disease including osteoporosis and osteoncus is expected to increase. In response to the situation, doctors use bone prosthesis or bone-graft substitutes that replace damaged or absent parts of the body as a treatment.
NGK SPARK PLUG CO., LTD. has implemented advanced techniques for ceramics in the form of sintered bone prosthetic materials, which are made by sintering materials incorporating the inorganic component of bones, and hardening-type bone prosthesis, which can fit to replace absent parts of the bones during surgery and harden in bodies afterward.
We have built trust and credibility with medical health professionals working on the leading edge of medicine. Currently we are creating new artificial bones that can support the function and have similar features of natural bones.

Sawamura:Involved throughout the entire process of the project such as development, communication with doctors, and clinical tests.

Mizutani:Engaged in the development of materials of artificial bones and devices used by surgeons.

Kasahara:Involved in the establishment of the production process based on sterility testing and the application for pharmaceutical approval.

Developing Artificial Bones to Satisfy Demands in Medical Treatment.

We are proud and happy to be able to bring back smiles to people in need─

NGK SPARK PLUG CO., LTD. makes a valuable contribution to people's lives and society by development of ceramic materials and components. The reason we expanded our business into areas related to production of medical equipment including artificial bones is to bring smiles to people in need all over the world with our materials and techniques.

We have developed ceramic bone prostheses such as Ceratite®, which is used to supplement a part that needs bone grafting, Cerapaste®, which is injected to missing part in order to repair and heal bone tissue, Cerarebone®, which is absorbed and replace missing bone or repair fractures, and also developed Zirconia femoral heads.

Doctors use Ceratite®, Cerapaste®, or Cerarebone® differently in surgical procedures according to each patient's case. This is because the structures and features of bones are quite different, for example, from leg bones to head bones. In addition, doctors may use bone prosthesis that are different from the materials previously used by other doctors even when treating same parts. Accordingly, the development is a truly complex process.

"Artificial bones not only need to be materials that bring back happiness to patients after surgeries, but we need to facilitate surgeries by our product development. In order to achieve this goal, technical skills, knowledge and capabilities in all areas are required," said Sawamura, who engaged in the process of the whole project.

Moreover, even though they are made of the same materials, when the manufacturing process is different, artificial bones sometimes can't create a same bone substitute. Sawamura emphasized that the manufacturing process making full use of materials is also our strength. "In that sense, Cerapaste® is our best representative product."

New Ceramics Made with Non-Fired Finishing Techniques.

It is necessary to control bone hardening while doctors are performing operation, and to harden soon when it is injected into a body in order to reduce the burden of surgical harms. So the main point is how we control the reaction rate.

Cerapaste® is a medical product made by mixing the powder of tetracalcium phosphate and anhydrous dibasic calcium phosphate with kneaded fluid in injectors. Then, it is injected to replace the absent parts of bones. It hardens in a body and finally becomes tightly integrated into the bone.
It needs to be soft until doctors inject it into absent part of bones and to harden after that. It is difficult to control the reaction rate at which it hardens. Ceratite® and Cerarebone® were developed by utilizing our ceramics shintering techniques, but as to Cerapaste®, we used a new technique that we had never used, because Cerapaste® is not hardened by firing them, but is hardened by a chemical reaction in the patient's body.

"During the product development, a fatal error occurred while working on it, and the bone hardening wasn't done properly although we had designed it to do so. We concentrated all of our energy on finding the cause."
Mizutani, who was in charge of the development of materials, conducted experiments over and over to achieve controllable reaction rate. However, in order to primarily ensure the safety of medical equipment, all we had to do was creating the best combination of materials and additives whose each safety had already been verified. Finally, after many trials and errors, Mizutani succeeded in coming up with the solution.

Mizutani had just joined NGK SPARK PLUG CO., LTD. when he also developed a dedicated injector in order to mix the powder with kneaded fluid, make it a paste and injected it into the body.

From Animal Tests to Clinical Tests.

After the development of materials, we faced challenges such as ensuring safety through animal tests and investigating the real effects and safety in cooperation with patients in "clinical tests."

The clinical tests determining the future of products started in 2000. They took place in five facilities commencing operations with the University of Tokyo, Faculty of Medicine, and the results were investigated. The applications in about 80 cases were confirmed. The target was "making a curettage procedure for a part of a bone tumor", "supplementing fracture parts" and "supplementing the gap part between an internal fixing material and bone."
As a result, the percentage of "very useful" was 82% and the one of "useful" was 15%, that is to say, 97% of all cases had the estimate of "useful" and above. The result was quite excellent for the outlook of the development and production of Cerapaste® as new medical equipment for doctors.

"After the clinical tests started, I felt very nervous because Cerapaste® was injected into a human body in a surgery. Although I had a confidence in the product, I had nightmares about the result every day." In those days, Sawamura spent tense days. However, he also tried hard to pass the clinical tests with tenacity.

There are lots of cases in which not broken bone but fracture can occur in elderly patients whose bones are weak. Their bone remains deficient due to the crash. When bone prosthetic materials are injected into the damaged part that is repaired completely, it then provides a better quality of life.
When Sawamura and his colleagues realized through clinical test that their effort could contribute to the quality of life of many elderly patients, they forgot all the hardship they faced in the product development.

From Manufacturing Guaranteed Bacteria-free Products to Developing New Artificial Bones.

It should be absolutely safe, because it is a medical equipment—
This is a Kasahara's passionate speech. He led the establishment of the process guaranteeing the biological clean of Cerapaste®.
"What I made the genuine efforts for was making the manufacturing process permanently germ-free and fulfilling the pharmaceutical industry's requirements in order to obtain the approval to use it as a medical equipment."

How the process can guarantee biological clean.
The product will be injected into patients' body, so if there is any bacteria in the product, it will cause an infection. Kasahara and his colleagues designed a manufacturing process whose purpose was to guarantee that each component of Cerapaste® such as materials or parts was germ-free. And they were mainly focused on making a system to verify whether the process regulations they had made were adhered to.
For powdered materials injectors, both the injectors and powdered materials should be manufactured as germ-free products. We applied another sterilization method to a container in which there can be a kneaded fluid to harden the paste and to a container in which there can be a fluid to adjust viscosity. We also applied another sterilization method to two injection needles. Only when they were kept germ-free, Cerapaste® can be a finished-product.
They said that it was a hard work but they thought it was not exhausting because it was what they could accomplish by themselves.

In May 2005, making the manufacturing process ended up with receiving an approval of production from Ministry of Health, Labor and Welfare. And about ten years have passed since we started to distribute the products in the market. The realization that they have greatly contributed to society triggered more of the project members' enthusiasm.

"We continually make further advances in our core technique of ceramics, and lead the development of artificial bones made from plastic," said Sawamura. It is completely new artificial bones technology using Poly Ether Ketone (PEEK).
PEEK has the highest-level heat resistance among plastics as well as an excellent chemical resistance. So it is widely used in the industrial field. It is notable that PEEK has a mechanical characteristic of low elastic modulus and high bending strength and these characteristics are very similar to natural bone. In recent years, mainly overseas manufacturers have promoted the creation of artificial bones. Its safety as a medical equipment has been already confirmed. There is a challenge in a characteristic of PEEK that it doesn't have bone-binding properties like natural bones, but if only we can add bone-binding properties to it, we can approach wider global markets with our products.

"Exploring the challenging field of developing artificial bones made from plastic is based on the successful experiences that have been made by taking utilizing our ceramics technique, and we enhance more the potential of NGK SPARK PLUG CO., LTD.," said Sawamura, and both Mizutani and Kasahara agreed with confidence.