3D printing a straighter smile

No longer is it necessary to be saddled with bracket and wire braces for consecutive years in order to achieve a straighter smile: people around the world can correct their teeth alignment using customized clear aligners, which are not only much more discrete, but can be removed without professional intervention. The growing adoption of clear aligners—the market was reportedly worth over $2 billion in 2019—is due in no small part to 3D printing, a technology which has enabled orthodontic labs and specialist companies to achieve customization on a mass scale.

Clear aligners, the beginning

Though non-metal aligner systems for teeth have been used to some extent since the 1940s, digitally driven clear aligner technology, as we recognize it today, was pioneered and popularized by two students from Stanford University. In the late 1990s, these students invented the Invisalign system, the first solution of its kind to rely on a single impression to create a series of digitally modeled aligners.

Align Technology, the company behind Invisalign, was for years the dominant player in the clear aligner market. This dynamic was upheld by the company’s many U.S. and international patents, which prevented competitors from gaining a significant foothold in the digital dentistry subsegment. When these patents started to expire, however, new players burst onto the market with clear aligner solutions that in some cases were more affordable and efficient. This, in parallel, sparked the participation of many 3D printing companies in the production of clear aligners, often on a mass scale.

How do clear aligners actually work?

Today, people around the world use clear aligner solutions for cosmetic orthodontic correction. But before we dive into which 3D printing companies are playing a key role in the production of said orthodontic devices, we want to first illustrate how the aligners actually work.

In succinct terms, aligners are used as an alternative to conventional orthodontic braces—it should be noted that they are not a suitable replacement in many cases—and consist of clear plastic shells that fit over the patient’s teeth and move them incrementally until the desired placement is obtained. Unlike wire braces, aligners can be removed by the wearer, making daily tasks like eating and dental hygiene practices easier.

Clear aligners are customized to the patient and are designed to be worn for up to two weeks (variably) before a new, slightly modified aligner replaces it. Typically, patients will have their mouth digitally captured either using an intraoral scanner or a scan of a physical impression. This scan data is then used to generate a 3D model of the patient’s teeth, which is used as the basis for the alignment planning. A series of aligners are then manufactured (using various technologies, as we’ll see), each with a slightly different shape to gradually straighten the teeth.

When worn, the clear aligners put slight pressure on the teeth that need straightening, which triggers a response from the jaw bone to move the tooth socket. The alignment process is designed to be comfortable for the wearer and is thus incremental, very gradually shifting the teeth in the mouth. If patients conform to wearing their clear aligners for most of the day (roughly 22 hours per day), smile correction results can be seen within a year in most cases.

Mass customization with 3D printing

So far, we haven’t really addressed how 3D printing plays a role in clear aligner manufacturing, but that doesn’t mean it isn’t critical. Today, most if not all clear aligner companies utilize 3D printing in the production of the patient-specific dental products. It has been a key enabler of customization on a mass scale.

Interestingly, there isn’t a dominant 3D printing process for the production of clear aligners, but the overall workflow is similar. That is, whether a clear aligner company is leveraging Stratasys PolyJet, HP Multi Jet Fusion, DLP or SLA technologies, most utilize 3D printing to produce a model of the patient’s teeth, rather than the final product itself. In most cases, the 3D printed orthodontic model undergoes thermoforming, a process in which a transparent plastic sheet is heated to the point of being pliable and is formed over the mold to create a final product.

3D printing is presently the only manufacturing process on the market that is viable for the mass customization of orthodontic aligners: other more traditional manufacturing processes would be far too costly. Further, 3D printing has enabled the production of multiple aligner molds at once.

Key players in 3D printing orthodontic aligners

In this segment, we’ll begin by first looking at one of the pioneers of digitally manufactured clear aligners: Align Technology, the company behind Invisalign. The company’s technology of choice in the production of its tooth-straightening products is 3D Systems’ stereolithography. The companies have been partners from the get go, leveraging 3D Systems’ 3D printing to produce custom molds for aligners for over 5.8 million patients. As of late 2018, Align Technology was operating an end-to-end manufacturing workflow capable of producing over 320,000 custom aligners per day.

Another key player in the clear aligner market is SmileDirectClub, a U.S.-based company founded in 2014. The company is the leader in the doctor-directed at-home clear aligner industry, meaning that customers can either have a 3D imaging session at one of the company’s many SmileShops or they can use an at-home kit to create intraoral impressions. SmileDirectClub produces millions of custom aligners for its clients around the world and leverages HP’s Multi Jet Fusion 3D printing to achieve these rates. As of last year, the teledentistry company was operating 49 MJF systems to produce over 50,000 unique mouth molds a day—up to 12 million a year. Notably, SmileDirectClub is the largest producer of MJF 3D printed parts in the United States. The companies are also establishing a recycling program that transforms unused 3D material and processed plastic mouth molds into pellets for injection molding.

Stratasys’ PolyJet 3D printing technology is used by more than one orthodontic aligner provider, including Straumann-owned ClearCorrect LLC and DynaFlex. The former has utilized Stratasys’ Objet Eden500V 3D printer since as early as 2015 to produce 100% of its custom aligner models. DynaFlex, for its part, is a Missouri-based specialist in orthodontics which has sought to scale up its production of clear aligners in recent years. Today, the company operates a 3D printing center equipped with several J700 dental 3D printers, enabling it to scale manufacturing of the models and realize on-demand production. Stratasys’ J700 solution is also employed by Malaga-based Ortoplus for “out-of-the-box” clear aligner production.

On the other side of the world in China, Hanyang Technology produces custom orthodontic aligners using EnvisionTEC DLP 3D printing. Other dental and orthodontic practices, including Cranston Orthodontics, also use EnvisionTEC’s technology to produce clear aligners in house. Other companies like Prodways and Formlabs have brought to market orthodontic aligner solutions which can be implemented by dental and orthodontic labs around the globe.

Prodways’ solution was launched in 2019 and offers a modular, highly automated process for producing dental aligners. That is, to boost productivity for the dental aligner market, Prodways combined its MOVINGLight ProMaker L Series 3D printers with robotics and automation technologies. Further, the company partnered with a clear aligner workflow software provider to integrate the solution. Prodways’ modular system addresses the entire production chain, from design, to 3D printing, to thermoforming, to packaging. According to the company, its automated production solution can produce over 2,000 clear aligners per day. Formlabs’ digital dentistry solution is designed to be adopted by dental and orthodontic labs and is based on its Form 3B 3D printer.

Is the future direct?

Though the direct production of clear aligners using 3D printing is not currently available, it is being explored for the future. For instance, Align Technology sees massive potential in the direct production of 3D printed aligners and is investing in their development. EnvisionTEC, for its part, which has brought many dental 3D printing systems and materials to market, actually unveiled a material for the direct 3D printing of retaining aligners, E-Ortholign, back in 2018 (at the time it was progressing through regulatory approval processes).