The 3D Printing Revolution

Many dental professionals feel that 3D printing will actually save dentistry. "Five years ago, we spoke about printing models; now, with rapid advancements, we are talking more about definitive prosthetics such as digital dentures, crowns, inlay/onlays, veneers, and implant-supported restorations," says Walter Renne, DMD, a private practitioner and Founder of the Modern Optimized Dentistry (MOD) Institute in Charleston, South Carolina. As digital workflows, materials, and technology develop, indications and new restorative solutions are offered to our patients. "When it comes to 3D printing, the person that wins the most is the dental patient," says Mauricio Lavie, DMD, MSD, a prosthodontist and Clinical Instructor in the Department of Postgraduate Prosthodontics at Rutgers School of Dental Medicine. In particular, the new advancements in nano-ceramics technology may transform how we think about restorative technology and 3D printing. "We can print a crown within 15 minutes that exhibits the esthetics and properties conducive to permanent prosthetics," Renne says.

The continuously increasing adoption of intraoral scanners—specifically for orthodontic treatments followed by restorative workflows—was the first impetus for dental professionals to seek an efficient, cost-effective way to produce a physical dental model, according to Chris Brown, BSEE, Principal Consultant at Aclivi LLC. "The 3D printing market for dental laboratories was initially driven by the prevalence of intraoral scanners, which necessitate model solutions," Brown says. Tran adds: "The majority of 3D printing innovation and the original driver within dentistry was clear aligners, because they presented the opportunity for mass customization and scaling. To this day, the leading clear aligner manufacturer is probably the largest 3D printing user in dentistry, producing upward of 400,000 models per day for orthodontic treatments globally."

As 3D printing evolved into a comprehensive solution within dental technology, innovations and newly emerging materials forged new pathways to manufacturing dental prosthetic solutions successfully and efficiently. "We have passed through the discovery phase," Brown says. "Similar to subtractive manufacturing, a period of time was required to get dialed in. The discovery phase allowed us to see what is needed, and it allowed manufacturers—both on the hardware/software side and materials side—to innovate and offer their solutions to the market. We have now hit the sweet spot in additive manufacturing with better printers and better materials, and that has driven even greater adoption. Whether it is the evolution of projectors and their significantly heightened resolutions, or other factors, the profession just loves the continued innovations and solutions."

Dental professionals need to be aware of how to produce efficient prosthetics through 3D printing, which has demonstrated a significant ROI. "At my practice," Renne says, "we normally print at least five night guard appliances per week; we have printed several hundred veneers that provide for same-day definitive restorations; and we have completely stopped directly bonding resins, simply because 3D printing options offer ease of fabrication and are better for longevity. We can print 10 veneers in 10 minutes, and they hold up better than the direct resin. All of our implant restorations have been 3D printed in the last 2 years, as they offer great shock absorption when compared with the alternative materials." The patient ultimately wins, Lavie says, because they enjoy fast turnaround with greater customization and a high level of accuracy. "As an example, for my denture patients, I can now quickly and easily print a couple of tooth libraries for try-in and it costs me very little additionally, but the patient can now select their smile in real time, rather than virtually on a screen," Lavie says. "I may try three different denture try-ins in one visit for the patient to select their ideal smile." Scenarios like these lend themselves to providing an elevated dental patient experience and an efficient use of the dentist's chair time. Printing fast-tracks the outcomes, whereby the patient and clinician can both benefit greatly, and the profession is changing to accommodate new workflows using these digital technologies.

As hardware and materials continue to evolve, so do output and accuracy. We can now print with a heightened level of accuracy at a very rapid pace. "3D printing has achieved better accuracy as it evolved from the first generation, and I am sure it will keep evolving," Tran says. Lavie says it is already sufficient. "Accuracy is absolutely there, without question," he says. The hardware, meanwhile, has advanced significantly across multiple platforms. "The resolution improvements have been tremendous and several published articles have indicated even better accuracy than subtractively fabricated prosthetics," Renne says. "The accuracy of 3D printers has exceeded that of mills, and it even rivals that of pressing or casting methods. When you have a photon with an X/Y resolution of less than 50 µm, you will never be able to achieve that level of accuracy in milling, especially with the new printers that have high pixel density voxel technology."

The printers also are getting faster and faster, and the ability to 3D print multiple crowns on the same printer presents a significant advantage over milling. "Printing wins with efficiency in quadrant dentistry, because milling even just four or five crowns, one at a time, takes hours," Renne says. "Printing four or five crowns—or maybe even more—can be accomplished in 15 minutes." The technology that produces higher-resolution 4K projectors—digital light processing (DLP)—allows for the ability to have 20 µm or even smaller resolution. "That could be the difference between an open or closed margin, contacts, etc," Brown says. "The first-generation technology allowed for a resolution of 100 µm, but today, the resolution is better, so the accuracy and consistency of the printed resins are indeed superior. Now, we have pixel sizes that can get to the 20- to 30-µm range, providing for more accurate models and parts, as well as greater detail in the actual prosthesis."

The open vs closed conversation is different for 3D printing. "Every system on the market can accept an STL file; open and closed in printing are different than milling by virtue of the system," Renne says, adding that all printers are open but some printer manufacturers will only use resins that they validate and are confident in to produce successful outcomes. "Certain companies spend a lot of money and time to validate these resins, following strict protocols because these will be used in the human body," Renne says, "so users should adhere to these validations and processes."

Some printing companies try to protect their processes through RFID tags—special chips in resin cartridges that are considered closed. This strategy is limiting, but it allows the manufacturer to control more of the process for a successful outcome. Open architecture, meanwhile, provides the freedom to choose the latest resin materials on the market. While Tran is an advocate for open architecture, he cautions: "The patient's safety is paramount and we need to make sure we are adhering to the validation and following the instructions for use (IFUs) to maintain the safety of the patients." An important component of 3D printing is the light cure box, and that also must be validated. "This is a much more complex issue with 3D printing," Brown says, "and that is why following the IFUs is so important. Biocompatibility is critical to ensure that validated printers with appropriate resins are cured with a validated light box. The FDA will take issue if you do not follow the IFUs. Not adhering to the instructions can very well lead to product failures, which will not be conducive to a successful future."

Resin materials are among the most significant recent innovations in the dental market, and they have led to the availability of better printed products with enhanced properties. "We are finding that, every year, more and more materials are biocompatible and effective for our dental indications," Lavie says. "There have been significant improvements in regard to printed material properties, durability, and toughness. The most impactful recent innovations are stronger resins with nano-ceramic fillers that are radiopaque and can be in the mouth for a long time." Tran adds: "On the resin side, denture materials will continue to evolve and get better, as will permanent crown resins, which look promising."

As of January 1, 2023, dental insurance companies changed their CDT coding to allow for reimbursement as a permanent crown for 3D printed resin crowns. "The viability and longevity of these types of permanent crowns remain to be seen," Tran says. "Personally, I am taking the ‘wait and see' approach on these." Resins are advancing rapidly and, unfortunately, often too fast for the research to keep pace. However, initial studies are promising. "Testing and published studies show that these materials bond better than milled ceramic materials with greater fracture toughness and wear resistance, and high levels of accuracy," Renne says. "Curing via the appropriate FDA-approved cycle and light wavelength, which constitutes a cleared and validated system, will produce a great prosthetic solution."

The CDT insurance code change indicates that if the material comprises 50% or more of inorganic filler particles, it could be coded as a ceramic restoration for insurance reimbursement. Because of this code change, Renne says, 3D printing manufacturers have invested millions more dollars in developing resins. It will ultimately reduce the costs for the patient—particularly those who rely on insurance—and create greater accessibility for dental treatment. "The nano-ceramic 3D printed resin properties remind me of gold material in the way the material wears and gives, and is able to be dynamic in the mouth," Renne says. "Other materials are very rigid and have no give, and perform like a rock in the mouth. This resin wears three times less than direct resin and wears equally to natural wear of dentition, which I am very excited about." Tran emphasizes caution, however. "Materials are typically tested in a dry environment," Tran says. "We know that the mouth is quite the opposite and the environment is very different than the way they are being tested in vivo. There is not much data available yet, but I believe ceramics will perform better than resin in vivo." Several new permanent crown materials are expected to enter the market in 2023. "Introducing nano-ceramic materials will ultimately come down to the resin bond, the material properties, and the chemistry involved," Brown says. "I look forward to seeing the research develop as it pertains to water solubility, water absorption, strength, and work of fracture. Having more materials optimized specifically for use in dentistry is very exciting and will further drive the 3D printing evolution."

Innovations continue to evolve and produce better material properties. "On the horizon, I anticipate better esthetic properties for dentures and crowns, and closed resin companies announcing that they are open for validation," Tran says. "Hardware will be more incremental, but the resin space is where I believe we will see the greatest innovation." Some manufacturers also are working on 4D materials, whose properties can change under certain conditions. These materials have a memory affect. "One company makes a smile clip and locks for implant components that, once subjected to heat or cold, respond and either open or close, which is a great benefit for patients who struggle with manual dexterity to remove their prosthetics to clean," Tran says. There will undoubtedly be more materials with creative indications in this space. "Multi-materials can be an exciting development in the future," Brown says, "whereby you might be able to commence printing and, mid-cycle, change the material or material property and continue the print job. It all depends on the science for viability. Evolution of 3D print materials will be the primary innovation in the coming years." Lavie says multi-materials would be more of a luxury than a need. "One day in the future, it might be more common," Lavie says, "but I do not think any indication needs multi-color or multi-material other than an attempt to solve the challenge with digital dentures of printing both the dentition and the denture base. I am more convinced that the integration of artificial intelligence will be the most impactful future development."

In the future, we can expect to see faster printing and artificial intelligence involvement to make nesting easier, more efficient, and more accurate. "You will also see printing ceramics," Renne says. "Two 3D printers currently on the market can 3D print zirconia, and some companies are looking at certain printable lithium silicate materials that are 99% ceramic after sintering or crystallization in a special way." Renne adds that he anticipates more and more definitive restorative resins entering the market, as well as further automated processes with faster printers and integrated workflows that have washing and post processes all streamlined and automated. Undoubtedly, the future is very bright for the dental profession as we harness these cutting-edge technologies, material properties, chemistries, and sciences in order to produce optimal prosthetics for our patients along with efficiencies and cost reductions for the dental laboratory and dental office.