An interview with Ms. Ban - 30 years of dental ceramics development.

The development of ceramic dental materials has a long tradition at Noritake Co., LIMITED (Noritake). It started in 1978, when Kiyoko Ban, who is a Technical Consultant at Kuraray Noritake Dental today, was a member of the teaching staff at the Tokai College of Dental Therapy in Nagoya, Japan. There, she trained her students in producing porcelain-fused-to-metal (PFM) restorations, and encountered the problem of porcelain fractures and cracks that often occurred after the firing process. Her desire to solve this problem resulted in the first dental porcelain development project at Noritake.

Failure analysis
Kiyoko Ban gives an account of her early activities: “I received many inquiries from dental technicians on why cracks occurred inside veneering porcelains of PFM during firing. I wanted to find out what was causing this problem. Hence, I started analyzing the available materials and manufacturing procedures. In the course of my research, I concluded that in order to obtain better results, it would be necessary to develop a new porcelain material with fundamentally different physical properties. The reason was that the physical properties of the
available porcelain materials were unstable. One problem was that the coefficients of thermal expansion of the porcelain were changing under varying firing conditions, and sometimes fluctuated even if the firing temperature remained constant. Due to the differences in the coefficients of thermal expansion of the metal framework and the veneering porcelain, high stresses inside of veneering porcelain were generated, which ultimately led to the observed cracks.”

Joining forces with Noritake
For support in her research, Kiyoko Ban approached a leading expert in the measurement of residual stress in ceramics, Dr. Hiroshi Inada. He was the Manager of the Research & Development Department at Noritake. Together, they decided to initiate a
joint development project. In the first phase, the market research was conducted in order to define the project aims. “We found that there were three factors that troubled dental technicians fabricating PFM restorations: cracks and fractures in the porcelain layer, limited reproducibility of the natural tooth colors and yellowish discoloration caused by silver in the framework material. Consequently, we decided to develop a crack-free material that was resistant to yellowish discoloration and matched the colors of natural teeth by offering a tooth-like fluorescence,” states Kiyoko Ban. She continues: “The first steps in the development process were relatively easy. We soon were able to ensure constancy of the coefficient of thermal expansion. The most complicated part, however, was to develop different material shades. As understanding and reproducing tooth color is a highly complex task, we collaborated with dentists and dental technicians. They evaluated the optical properties of our trial formulations and helped us improve them until they were satisfied with the outcomes. This process took us three years and finally resulted in the 16 material shades launched in 1987.”

Image  2: The product launched more than 30 years ago: Noritake Super Porcelain AAA.

The name – Noritake Super Porcelain AAA – was suggested by the former Vice President of Noritake and at that time Managing Director, Motoki Nawa. It refers to the three basic needs it satisfies, and expresses that the product aim for becoming class A. Noritake Super Porcelain AAA became available in Japan, where Morita Corporation became the distributor. Soon, a network of instructors was established and training courses were offered to ensure technicians would use the product in the best possible way. Within a very short time, the product got a market share of approximately 30 percent. At this time, Noritake Super Porcelain AAA also started to conquer overseas markets (where it was given the product name Noritake Super Porcelain EX-3). Until today, many dental technicians around the world favor the porcelain material.

Additional shading options
One of the instructors who taught the use of the material worldwide was Hitoshi Aoshima, a representative of Perla Aoshima. He was famous for his excellent technique in the fabrication of porcelain restorations. Kiyoko Ban approached him at the 15th anniversary symposium of the international journal of dental technology in Tokyo in 1988, and initiated what would soon become a fruitful collaboration: “I decided to visit him in his laboratory soon after our meeting and provided him with a complete Noritake Super Porcelain AAA kit. One month later, during my second visit, he suggested developing porcelain stains, which do not generate air bubbles during the firing process even when you stain inside the veneering porcelain. This would enable dental technicians to imitate the complex color of natural teeth easily. We started working on the project immediately. With the support of Hitoshi Aoshima, our efforts came to fruition, resulting in the introduction of the product Internal Live Stain.”

Eyeing the next step: Research into zirconia
With the growing interest of dental technicians in porcelain materials, Kiyoko Ban was moved to predict that in the future, ceramics would evolve to become the preferred restoration material. She began investigating suitable ceramics and mmanufacturing technologies. In November 1998, Noritake’s Development Division and Noritake Dental Supply initiated a joint project to develop a new dental zirconia. “As a ceramics company with 15 years of experience in the field of industrial zirconia, Noritake foresaw that zirconia was going to be the next leading dental material. Consequently, we started developing the raw materials. Thanks to our high level of know-how in ceramic materials, we were soon able to present a new dental zirconia having less deformed after sintering. We observed the material trends and market needs for a while, and finally decided to go for finer esthetic properties and develop multi-layered disc. The product – KATANATM Zirconia ML – was introduced at the International Dental Show 2013 in Cologne, where it made a spectacular debut. The product received worldwide recognition. Today, three variants of the multi-layered discs are available. They offer different levels of flexural strength and translucency to meet the requirements oof various clinical situations.

Image 3: Launch of KATANA™ Zirconia ML at the IDS 2013.

Towards the future
More than 30 years after its launch, Noritake Super Porcelain AAA is still the product of choice for many ceramists around the globe. “With satisfied users in approximately 100 countries, I am happy to conclude that we have succeeded in developing a PFM porcelain that is virtually trouble-free,” says Kiyoko Ban. “Due to the success of the development projects, so far, in the field of dental ceramics, we are highly motivated to keep on developing new products that satisfy the needs of dentists, dental technicians and patients alike.” Kiyoko Ban, Kuraray Noritake Dental’s Technical Consultant, is still working hard to help enhance treatment outcomes in dentistry and contribute to an improvement of oral health.