Solution partner of measurements in interfacial chemistry: Kyowa Interface Science

Dr. Mari Koike, Director of the Clinical Research Support Office, Nippon Dental University, and the interviewer from Kyowa Interface Science (from left).

In dentistry, titanium is gaining attention as a material with a low risk of metal allergies. In recent years, the development of 3D-printed titanium dental materials has been progressing rapidly.

Dr. Mari Koike, from the Clinical Research Support Office at Nippon Dental University and an expert in prosthodontics, is at the forefront of research exploring how these titanium materials can be applied in dental treatments.

In this interview, we spoke with Dr. Koike about how our contact angle meter has been utilized to address one of the key challenges of 3D printing – surface roughness – and to evaluate how well these materials integrate into the oral environment.

The Start of Research Focused on Titanium Safety

――― First, could you tell us about your specialty and what got you started with titanium research?

Dr. Koike: My specialty is prosthodontics, which basically involves making dentures and dental crowns. In general practice, we often use cobalt-chromium alloys or gold-silver-palladium alloys. However, some patients experience metal allergies to these materials. That is what led me to start using titanium as a safer alternative, and that is how my research began.

Titanium is considered a safe material because it does not readily corrode in the body. But I wanted to understand how it behaves in the mouth's salty environment and explore ways to make it easier to use in dental applications. That has been the focus of my research.

――― How has the technology for working with titanium evolved over time?

Dr. Koike: Titanium has a very high melting point of around 1,860℃, so it could initially be processed only with specialized casting machines. Later, digital methods emerged, where shapes could be scanned and designed on a computer before manufacturing. Today, the third major method is 3D printing.

In 3D printing, layers of titanium powder are spread and then fused with a laser or an electron beam. Because the process is fully digital, it is expected to reduce patient burden and improve treatment efficiency.

Challenges of Surface Roughness Unique to 3D Printing

――― Are there any challenges that are specific to 3D printing?

Dr. Koike: Yes. Because 3D printing builds objects from powder, the heat may not fully melt every particle, leaving the surface uneven. For materials used in the mouth, the surface needs to be smooth and resistant to buildup, such as biofilms.

▲Samples and metal materials used to evaluate differences in surface properties depending on 3D printing method.

Another factor is the printing angle. Surface roughness can vary depending on the orientation of the object during printing. For example, printing at 0 degrees (horizontally) versus 90 degrees (vertically) affects how the laser hits the powder, which in turn affects the surface finish. So, it was crucial for us to carefully evaluate how the printing method and angle influence the surface characteristics of the final product.

Visual Impact Changed the Direction of the Research

――― So that is when evaluating surface characteristics became necessary?

Dr. Koike: Exactly. Alongside properties like strength and corrosion resistance, I had always wanted to investigate the "surface tension," or wettability, of the material. I remember seeing presentations at conferences where they dropped a liquid droplet on a surface and showed how it spread, and I thought that was fascinating. But at the time, I did not know who I could consult to actually measure it. By chance, I met a sales representative from Kyowa Interface Science at an exhibition. He suggested, 'Why don’t we try measuring it?' I left him some samples, and that became the start of our ongoing collaboration.

――― What significance did the contact angle measurements have for your research?

Dr. Koike: As we progressed, I already knew that surface roughness varied with the printing angle. But when presenting this in papers, just stating numbers like "the roughness differs" did not really convey the difference to readers. When I saw the droplet images provided by the team, it was immediately clear visually: "Yes, these two surfaces are definitely different."The visual impact was huge.

――― So both numerical data and visual information were important.

Dr. Koike: Absolutely. Just saying "the contact angle is X degrees" does not really give a clear picture. But if you show a photo where a water droplet is perfectly round versus one where it spreads flat, you can intuitively understand what the numbers mean. As the saying goes, "seeing is believing", and being able to visualize it is extremely important. What impressed me most about the team was Kyowa's thoroughness. Unlike other measurement services, which often provide results from a single measurement, Kyowa conducted multiple measurements to ensure reproducibility. Kyowa carefully checked the data for variations and provided meticulous support.

Thanks to Kyowa's efforts, we were able to express the surface roughness both visually and numerically in my papers, achieving exactly what I wanted with the materials. Although the droplet photos could not be included in the conference posters due to space limitations, the visual information from these measurements significantly enhanced our understanding of the research.

▲Excerpt from the evaluation report prepared for Dr. Koike on differences in surface properties by build method (partial extract).

Establishing Standards for Use in the Oral Cavity

――― How are the measurement results being used?

Dr. Koike: Measuring the contact angle is extremely important as a way to evaluate material properties, as we did in the paper we published. From this research, we gained insight such as, "With this level of roughness and this kind of surface condition, the contact angle will generally be around this value." This knowledge serves as a useful standard for determining whether 3D-printed titanium can actually be used safely and effectively in the oral cavity.

Aiming for Strong Collaboration Between Researchers and Companies

――― As the director of the Clinical Research Support Office, you also support other researchers, right?

Dr. Koike: Yes. Alongside my own research, I help others who may not be familiar with statistics, and I assist in building "connections" with external companies or experts, similar to what I have done myself.

Since graduating, I have not had many opportunities to learn new things, so I often attend seminars to keep my knowledge up to date. When webinars began during the COVID-19 pandemic, they were especially useful because I could participate without having to travel.

――― What do you think about our webinars and other information sharing?

Dr. Koike: "Collaboration between companies and researchers is really important."

In that regard, I think your seminars at Kyowa Interface Science are excellent. Often, seminars from other companies end with a pitch like, "You can only do this with our equipment," but your seminars rarely do that.

As a researcher, I want to hear a balanced mix of basic concepts and specialized applications. Continuing to share a variety of information — including cases like mine — can give other researchers hints and ideas, like, "Oh, this is one way to do it." I also hope to act as a hub myself, so that when someone is struggling, I can say, "Here is a method you could try."I look forward to continuing good collaboration in the future.

Related Paper

Below is the abstract of the paper describing the present study, for which Dr. Koike served as the first author.

Surface Morphologies on an Additive-Manufactured Titanium Alloy for Biofilm Formation
(2024 IADR/AADOCR/CADR General Session)

https://iadr.abstractarchives.com/abstract/24iags-3998155/surface-morphologies-on-an-additive-manufactured-titanium-alloy-for-biofilm-formation