3D printing is a hit in the mouth

Has a new technology been crowned in dental production?

Cobalt-chrome is a good material for dental parts because it can withstand continuous force and has good wear resistance. Photo courtesy of 3D Systems.

Additive manufacturing (AM) can be a faster, cheaper, and simpler way to make metal dental parts when compared to conventional machining. AM advocates also say that metal 3D printing is more precise, consistent, and customizable than subtractive machining while creating less waste.

While the AM production method is rare in North America, using metal 3D printers to make dental parts is extremely popular in Europe, according to Rik Jacobs, vice-president/general manager, dental for 3D Systems.

This popularity stems from high European labour costs and a shortage of skilled dental machinists capable of making parts the traditional way. To survive, European dental labs invest in automation. To combat these trends, labs are increasingly incorporating 3D printing into their daily work flows.

The beginning

Dental parts production typically begins in a dentist’s office.

“Normally the patient has an appointment at the dentist [and] a tooth imprint is created,” explained Roland Spiegelhalder, product manager, additive manufacturing North America, TRUMPF.

Imprints traditionally are created by putting dental impression trays containing silicone against a patient’s upper and lower jaws. The resulting impressions are filled with liquid plaster to mould a cast (also called a model), which serves as a template for production.

In a traditional machining scenario, dental parts are shaped by either die casting or milling. Depending on the part and complexity of the job, the entire process—from the dentist’s chair to final fitting in the patient’s mouth—can take days or even weeks.

In an AM application, the dental impression cast is scanned. If the dentist has a manual dental scanner capable of capturing 3D images of a patient’s mouth, the entire casting step can be skipped. Scan data is utilized to create a digital CAD model for part design purposes. Once a part is designed, the CAD file is transferred to a 3D printer. Metal 3D printing software then prepares the digital model for processing.

“You press the start button and the machine starts [working]. It’s really no work at all at that point. You can easily run overnight, and in the morning, the part is ready,” said Spiegelhalder.

During AM production, a thin layer of metal powder is spread, and a laser melts the particles together, creating a “slice” of the part. The process is then repeated until the whole part is built up layer by layer. Eventually a solid part is detached from the build plate.

Fixation plates and surgical guides used in oral and maxillofacial surgery are examples of dental parts now created using additive manufacturing. Images courtesy of ADEISS.

When metal dental parts are the products being printed, some finishing with traditional machining methods is required to gain the necessary finish requirements.

Traditionally thought of as a slow means of production, AM for dental applications actually can be quite fast.

“A TruPrint 1000 [3D printer] can do around 80 to 90 units, which means crowns and bridges, in three hours. It’s a really fast technology to make parts because there’s not much machining needed at all,” said Spiegelhalder.

This relatively short printing time also means 3D technology can cost less.

“In traditional dental work, a lot of craftsmanship is involved. People need a lot of time. You have to make a mould and pour in material. [Now] you are more productive and at a lower cost per part,” said Jacobs.

Biocompatible metals

Cobalt-chrome and titanium alloys currently are the most prevalent metals used for metal 3D dental parts. In general, metal parts that go into your mouth, including bridges, dentures, and crowns, usually are printed from cobalt-chrome. Conversely, anything surgically implanted in the body that connects with bone usually is made from titanium.

“Dental implants, which are basically screws, are typically done in titanium because it is good for bone ingrowth. With regards to denture structures, you may use cobalt-chrome because that sort of surface is going to be under continuous force. You want to ensure there’s low wear happening,” explained Dr. Yara Hosein, technical manager at the Additive Design in Surgical Solutions (ADEISS) Centre.

Based in London, Ont., ADEISS is eager to promote 3D metal printing as a viable option for making dental parts.

“We were launched back in 2017 with the idea of supporting research commercialization. We’re owned by Western University here in London and we’ve had extreme support from Renishaw. We were set up with the intention to basically support any sort of innovations happening here in London at the university and teaching hospitals,” said Hosein.

The centre’s work is highly market-focused.

Dental partials are good candidates for additive manufacturing using cobalt-chrome. Photo courtesy of 3D Systems.

“With the utilization of 3D printing technology for metal specifically, the idea is that we could support taking [certain] innovations through the pipeline all the way to commercialization,” said Hosein.

Operating by ISO 13845 standards for medical device manufacturing, ADEISS is equipped with a pair of Renishaw laser powder bed AM 400 3D printers. One printer is used to process cobalt-chromium alloy (F75), while the other uses titanium alloy (Ti6Al4V).

“The metal 3D printers can produce 200 to 400 units per plate. This could take anywhere from eight to 12 hours with a single laser, or half that time with a four-laser system,” said Mark Kirby, additive manufacturing business manager at Renishaw.

For its part, ADEISS also has 3D-printed custom fixation plates used for jawbone reconstruction surgery.

The centre hopes to grow its presence and assist companies, medical manufacturers, dental labs, and other health-care facilities interested in using 3D printing to create metal dental parts.

The benefits of this technology are quite clear, as far as Hosein is concerned.

“A problem with [traditional dental] casting is that it’s such a laborious process. There’s a lot of steps and technician time. If you can limit some of those steps, you can cut down on the time required,” she said.

Hosein also noted that 3D printing can be used to create part details and designs that would be difficult to achieve with subtractive machining methods. Also, metal 3D dental parts can be easily customized.

“3D printing can allow for the fabrication of intricate, small structures, like lattice structures. It can make very intricate and unique custom devices for humans. That’s why [the technology] works really well, because a lot of dental devices are patient-specific,” she said.

Reducing scrap

Unlike conventional machining, very little scrap is produced in 3D printing. A 3D printer can be loaded with the precise amount of metal powder needed to create a part, and no more.

“With regards to subtractive machining, milling is pretty commonly used in dentistry. It works well, but I think the one thing with milling is that you have a lot of waste material. So, you have a block that you then mill to get the final part. One advantage of 3D printing is there’s minimal waste,” said Hosein.

As Spiegelhalder notes, additive manufacturing systems can run unattended in lights-out fashion.

Also, 3D printing provides excellent digital traceability.

This is not to say that 3D printing is going to replace conventional machining any time soon in the metal dental parts sector. On top of the fact that metal 3D dental parts still require finishing, the initial investment is steep, and the process isn’t suitable for small volumes.

A 3D printer “is still somewhere around the $1 million mark, depending on what kind of machine you get. If you have a demand for 200 metal dental copings a day, 3D printing them makes sense. When the demand is 20 a day, which is more typical for a lab, maybe some of the existing [machining] techniques work just fine,” said Kirby.

That said, it’s a safe bet that metal 3D printing will grow in popularity in Canada. In the most likely scenario, dental labs that do large production runs will start incorporating 3D printers into their equipment lineups. As an alternative, facilities such as ADEISS could take up metal 3D printing duties for labs or companies that find the purchase price of a 3D printer prohibitive.

Regardless of how things unfold, it seems certain Canadian dentists and dental labs will increasingly use 3D metal printing technology.

“Dentistry and 3D printing work very well together because of the custom nature of the devices being designed and produced. As printer prices drop and productivity increases, more dental labs will employ the technology. Undoubtedly dentists will continue to use more and more metal 3D-printed parts. This includes products that are a hybrid of printing and milling,” said Kirby.

Contributing writer Nate Hendley can be reached at nhendley@sympatico.ca.


3D Systems, www.3dsystems.com

Additive Design in Surgical Solutions, www.adeiss.ca

Renishaw Canada, www.renishaw.com

TRUMPF, www.trumpf.com