By Liz Stevens, contributing writer, UV+EB Technology
Headquartered in Chicago, Illinois, Myerson LLC, founded in 1917, is a manufacturer of high-quality, aesthetically appealing denture teeth. The company specializes in the removable prosthetics market: in addition to denture teeth, it offers materials and equipment for fabricating flexible partial dentures and sleep appliances.
The company is earning attention for its innovative use of UV curing of a patented plastic resin formula used to create ultra-strong, natural-looking permanent replacement teeth. Jim Swartout, Myerson LLC’s CEO, described the industry’s history and the collaborative journey that led to the company’s 3D-printed, UV-cured dental appliances.
In the early 1900s, ceramic (specifically porcelain) became the material of choice for replacement teeth. Ceramic teeth are affixed by hand into the denture base material, using a tiny gold pin to anchor each tooth. The rising price of gold and the labor-intensive nature of the assembly process made this method increasingly prohibitive and, in the 1960s, the industry embraced the ’60s miracle substance: plastic. Heat-polymerized polymethacrylate – natural-looking and affordable – became the world’s favored tooth material.
In the last decades, the baby-boomer population has created a surge in demand for replacement teeth and, simultaneously, the tooth-setting craft has declined dramatically. As with other industries eager to modernize, dentistry began to embrace digitization. The traditional method of making of dental impressions, for example – utilizing a platter of soft silicone – is giving way to digital wands that record the contours of a patient’s gums and teeth. For the manufacture of replacement teeth, CNC milling has become the mainstay, and while it is fast, it also has limitations and is wasteful of materials. Additive manufacturing has looked attractive for dentistry, but it is only since the cost of printers has dropped and CAD software has matured that it has become a feasible avenue to explore.
Dental laboratories began buying 3D printers early on but, until just recently, they were used mostly for process material for in-lab use rather than for appliances in a patient’s mouth. Jim Swartout explained that one big reason the industry has not yet fully jumped onboard with 3D printing for dental appliances is “the materials have not met the need. They have tended to be very short-term as opposed to being suitable for permanent use in the mouth – which is a very challenging environment for any material. The first generation of 3D material was not sufficiently tough and didn’t have the right aesthetic qualities for it to be widely accepted.”
Twelve years ago – Hybrid Ceramics, a San Francisco, California, company led by a dental bio-materials specialist and a prosthodontist – presented Myerson LLC and Swartout with a new and improved plastic material for making conventional, heat-cured denture teeth, and asked if the company would like to use it.
“We spent 10 years,” said Swartout, “trying to take this highly advanced formula and put it into a 1960s-based manufacturing process for heat-curing false teeth.” Three years ago, Swartout brought the trend toward digital manufacturing in dental labs and the dental industry to the attention of his business partners. “I said 3D printing is where people ultimately want to go. So instead of buying prefabricated denture teeth, for example, they would want to be able to print them on-site, right away, using 3D resins.” Swartout wondered whether the improved material created by Hybrid Ceramics, which has some remarkable mechanical properties, could be converted to a 3D printing material. He checked with Hybrid Ceramics. “The bio-materials expert said ‘I think it would make an excellent printing material,’ and that’s what really started us on our journey.”
A host of unique mechanical properties is necessary for dental applications since the human mouth is a complicated environment, and teeth must withstand extraordinary pressures. The new printing material created through Myerson’s collaboration with Hybrid Ceramics has extremely high mechanical properties, comparable to engineered polymers like PEEK, which is used for orthopedic implants.
With this patented-formula material, said Swartout, “you can achieve incredible toughness that’s retained in the presence of water.” Other materials might be tough, but they may not remain tough in the watery environment of the mouth, or they might not be bio-compatible, or they might not look nice. Swartout explained that replacement teeth must withstand sudden or prolonged biting force without cracking or deforming, which calls for high strength plus some flexibility. They also must have a low rate of absorption to resist picking up stains or odors from food and beverages. “The unique thing about this material that Hybrid Ceramics developed,” said Swartout, “is that it is very tough, it maintains that toughness in water and you can make dental materials out of it that look very natural and are almost indistinguishable from human teeth. The ability to do all of those things is what is unique.”
Swartout described that the biggest challenge during the multi-year project was the team-building angle. “We’ve been in business for over 100 years, but it doesn’t mean that the relationships we built over time were the right relationships to advance this technology. I had to build an entirely new network of advisers and people to help bring this project along at a fast pace.” To develop a resin material with specific properties that was also amenable to 3D printing, Swartout had to build a network of scientific and business advisers to help commercialize a radically new dental application. “We had to find the best people in their fields to help us. It’s still a new area in dentistry, so the experts weren’t falling out of trees.”
The team considered DLP printing but realized that – while this method is portable, fast and predictable – it does not easily allow for working with multiple colors. Natural-looking replacement teeth need to have the translucence and variation in color that matches real human teeth. 3D inkjet printing was chosen since it can work with multiple colors. UV stood out as an affordable curing method that delivers the high quality required for medical devices. Swartout pointed out that the UV wavelength employed for this project is based on standardization and availability. “The first wave of 3D printers tended to be in the 405 nm wavelength,” he said, “because it was affordable and fast and accurate. You are seeing more and more 385 nm printers because they are able to be even faster and still deliver excellent resolution. Our job is to tune our formula to those two standard platforms – the 385 nm and 405 nm.”
Myerson LLC’s plan, which was delayed somewhat by the pandemic, is for beta testing of the new material and 3D printers during the last quarter of 2020 and commercialization in the first half of 2021 in dental laboratories within the company’s existing network.
RadTech, the nonprofit for UV+EB, celebrated the 2020 Emerging Technology Award winners at the RadTech 2020 Conference, March 8-11, in Orlando, Florida. RadTech’s Emerging Technology Committee selects award winners among end users of the technology, based on new, promising and/or novel use of UV and/or EB. RadTech has recognized applications ranging from 3D printing/additive manufacturing to floor coatings to novel electronics to unique uses for automotive and aerospace. Myerson LLC was one of the 2020 Emerging Technology Award winners.