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Inside Dentistry
July 2020
Volume 16, Issue 7

3D Printing Goes Chairside

Efficient in-house manufacturing of models, guides, dentures, and more

Jason Mazda

Michael D. Scherer, DMD, MS, owns nine 3D printers. And yet, the California prosthodontist says, "There is always room for more." That is because 3D printers come in all shapes and sizes. Some cost less than $5,000, while others cost six figures. Some are built for extreme precision, and others are built for volume and speed. Regarding the technologies enabling 3D printing, there is Digital Light Processing (DLP), stereolithography (SLA), MultiJet printing (MJP), fused deposition modeling (FDM), selective laser sintering (SLS), selective laser melting (SLM), and other methods. Perhaps most importantly, the advantages and disadvantages of each vary by application, from models and surgical guides to digital dentures and more. The future appears endlessly promising. "If you have a sparkle in your eye to make something really cool and distinguish yourself as a dentist," Scherer says, "then you are ready for 3D printing."

Entry-Level Applications

Each practice's needs are different, but several of the most popular chairside applications for 3D printing are relatively user-friendly and can be printed on low-cost machines.

"Good printers are available in the $4,000 to $10,000 range," says Marko Y. Tadros, DMD, a prosthodontist in Atlanta, Georgia. "You can achieve a strong return on investment within a year."

One of the oldest and most common applications is printing models from digital impression scansa practice that was referenced in this journal as early as 2009.1

"Instead of taking alginates and pouring them up, I can use an intraoral scanner and print models quickly," says David W. Honey, DMD, a general dentist in Libertyville, Illinois. "Instead of pouring and trimming the models, assistants can sit at the computer. There is less work."

Richard Sullivan IV, DDS, a general dentist in Brentwood, Tennessee, says that he sold off all of his impression trays this year because he went fully digital.

"Printing models is the most common application on a day-to-day basis," says Sullivan, who had been scheduled to present "3D Printing for the Everyday Dentist" at this year's Thomas P. Hinman Dental Meeting before it was canceled. "The workflow is more efficient, the models are stronger, and unlike a stone model, the file is saved and can be reprinted if necessary."

Printed models also can be leveraged for orthodontic applications, using the "suckdown method" to fabricate clear aligners. Walter G. Renne, DMD, assistant dean of innovation and digital dentistry at the Medical University of South Carolina College of Dental Medicine, notes two distinct workflow options. One involves designing the aligners in-house, exporting the STL files at different stages, printing them, and executing quality positive-pressure suckdowns to make the aligners. Alternatively, a hybrid model can be employed, which involves contracting a laboratory or design service for the tooth movements and then printing from those STL files in the office.

"Both workflows dramatically decrease the cost to the clinician," Renne says. "We are able to avoid passing those expenditures on to the patient and, at the same time, increase our profitabilityespecially because we can typically utilize other team members for parts of the workflow so that the dentist does not lose chairtime."

Honey notes that a workflow can be set up that allows the patient to leave with his or her aligner the same day. "You can scan the patient, have an assistant design the aligner, and print it very quickly," he says.

He also notes that certain manufacturers charge upwards of $1,500 to $1,800 per case for clear aligners, but that the cost of fabricating them in-house is approximately one-quarter of that. "You can save more than $1,000 per case," Honey says, "so after only a few cases, you have paid for the printer."

"The time and cost savings also extend to any necessary revisions, which can set a case back several weeks when working with a third party," says Rick Ferguson, DMD, a private practitioner in Davie, Florida. Ferguson notes that the flexibility afforded by in-house production can allow dentists to set a more acceptable price point for minor cases, such as those involving lower anterior crowding, which typically have lower rates of treatment acceptance.

Another application that can realize dramatic cost savings is the in-house printing of implant surgical guides, for which free design software is available.

"The cost savings associated with printing surgical guides is profound," Renne says. "Ten years ago, we were spending approximately $400 each for surgical guides that were designed and printed by third parties. Now, with just a few clicks of a button, we can have the implant planned in the perfect location with the restorative treatment plan based off of a DICOM data set. We can then export the STL file and, in another click or two, have it printed and ready to go for an all-in cost of $5 to $10. It is a fundamental paradigm shift to be able to offer that level of quality without passing along additional costs to the patient."

Surgical guides also are among the applications that offer the best quality when printed. "Digitally planned, 3D printed surgical guides are more precise than those that are fabricated with analog methods," says Paul Zhivago, DDS, a prosthodontist in Westfield, New Jersey, and the director of digital dentistry in the postgraduate program at the New York University College of Dentistry. "Certain printing materials can be brittle, but for the most part, it is a one-to-one comparison with analog if the correct thickness is used. And the cost savings are enormous."

Zhivago was trained as an implant surgeon and completed an implant fellowship at Columbia University under Dennis P. Tarnow, DDS, so he says he feels very comfortable placing implants without the help of a guide, but he prints them anyway. "Such little effort is required, and they are so cost-effective," Zhivago says. "Even if it is not a full rigid guide with metal sleeves, I print a guide for orientation for every surgery. The cost is so negligible that we do not charge patients, and it takes only 20 to 30 minutes at most to print them on a DLP printer."

Sullivan notes that, even if a dentist prefers not to design surgical guides, third-party design services typically charge only $20 to $30 per guide. "We literally just print it," Sullivan says. "It is very efficient."

In addition to the cost savings, the time efficiency of printing guides in-house is difficult to match when compared with using a third party to print. "I can have a patient come in during the afternoon on the day before a 7:30 AM surgery and have a surgical guide printed and ready to go for that surgery," Sullivan says.

Another same-day service involves the printing of temporary restorations. Ferguson notes that although they are not as strong as conventional temporary restorations right now, they are sufficient for short-term use, and longer-term materials will soon be available. "Printed temporary restorations are especially useful for mock-ups to increase patient acceptance," he says. "You can quickly do a digital mock-up yourself or outsource the design and then print in-house. When the patient accepts the treatment, you can send that mock-up to the laboratory to use as the basis for the final restorations."

Occlusal Guards

Similar to surgical guides and orthodontic models for clear aligners, printing occlusal guards can prove to be very profitable for dentists; however, the design is important and not always easy.

"Many dentists want to print occlusal guards, and the resins are good enough," Sullivan says. "The challenge that I have experienced involves obtaining good designs. Dentists and assistants need to become more familiar with third-party software programs, and once they do, articulating models and fabricating high-quality occlusal guards can still be difficult. There will be dentists who want to do all of their designs themselves, but from an efficiency standpoint for a busy practice, outsourcing the design often makes more sense. You still get the benefits of time, efficiency, and lower cost by printing that design in-house."

Scherer agrees that attempting to design occlusal guards in-house is not always wise.

"Design challenges should not be a limitation for dentists," Scherer says. "There are so many great design centers. Within 24 hours of scanning the patient, you can have a high-quality occlusal guide design ready to pop into your 3D printer."

Digital Dentures

Another more complex application is the fabrication of dentures. Both the denture base and the teeth can now be 3D printed, and the manufacturers of these materials continue to innovate to provide strength and esthetics that rival milled and analog production methods.

"When you mill a denture," Renne says, "arguably, you are getting a much higher-quality product. The resins have been heat-processed under high pressure, so they are denser, stronger, and more biocompatible; however, you pay a premium cost. A $5,000 to $10,000 printer can fabricate quality dentures. Manufacturers are constantly improving their resins to be stronger and more esthetic. We are seeing reinforcement of the fibers in the resins for strength and the development of multitranslucency printing for esthetics, but we are just scratching the surface. I envision that milling will be obsolete in 10 yearsmaybe even 5."

Arguably, the most popular printable denture material currently on the market can only be printed on one type of machine,2 and the cost of that printer is easier for a dental laboratory with high volume to justify. So, for the time being, many dentists are utilizing lower-cost options to print immediate/temporary dentures.

"You can literally scan a patient, start extracting the teeth virtually, design the denture, and print it while the procedure is being performed," Renne says.

One of Honey's patients brought in a broken denture that she had glued together, and he was able to scan it and immediately print a new one for her to wear to a job interview the next day. And Zhivago once had an edentulous patient walk into his practice at 9 AM for an impression and walk out at 5 PM with full upper and lower dentures.

Ferguson notes that during the COVID-19 shutdown, some of his patients wore their temporary dentures longer than usual, and none fractured. "If you follow the rules in the design process and make it thick enough," he says, "the dentures can be worn for 6 months to a year."

Despite these advantages, the consensus still seems to be that dentures printed chairside are not quite ideal regarding strength and esthetics. "They tend to be more brittle and fragile at this point in time, so they break faster," Zhivago says. "There is definitely some work to be done on the part of the manufacturers to enhance the amount of elasticity. Although traditional denture making was more of an art form, with five appointments, waxing up, festooning, etc, conversely, why should we not offer this type of service at this type of price? I am very happy that this option is available. Nearly all patients can now afford a quality denture."

What's Next?

The next major frontiers of 3D printing in dentistry will likely involve permanent restorations and clear aligners.

Although the US Food and Drug Administration (FDA) has not yet cleared any 3D printing materials to be used for permanent restorations, at least two European manufacturers offer them. The German company BEGO offers VarseoSmile Crown plus, a tooth-colored ceramic-filled hybrid material for 3D printing permanent single crowns, inlays, onlays, and veneers.3 And Austrian manufacturer Lithoz produces the CeraFab 7500 Dental, which prints LCM 3Y-TZP zirconia crowns using lithography-based ceramic manufacturing (LCM), a modified form of DLP-style printing.4 Several other companies are developing zirconia printing, as well.

The printing process for zirconia utilizes the same principles involved in SLA, DLP, resin jetting, SLS, SLM, and extrusion technologies.4 The post-processing is where it gets complicated because zirconia restorations emerge from the printer in a green state and must be pre-sintered and sintered.4 These post-processing steps are more cumbersome for printed zirconia than for milled zirconia, although volume can offset this factor in a printer that can produce several units in one build cycleas DLP printers can.

"Printed permanent restorations could be a game changer, especially if you could print multiple crowns at one time," Honey says. "I am a big proponent of chairside milling, but each crown needs to be milled for 4 to 5 minutes and then fired, whereas 20 crowns can be printed in one 20-minute session."

Of course, one advantage that milling offers is the use of multilayered discs. However, the capability to produce a multilayered result could be on the horizon for 3D printing. MJP technology already allows for the printing of multiple materials in one build.5 DLP printers can only hold one material in each vat of resin, but a new solution being developed utilizes segmented wavelength, or multimaterial actinic spatial controla technology that incorporates two projectors in a single machine to cover different wavelengths, enabling the use of two photoinitiators in a single vat.5 Another strategy being developed to vary translucency involves the manipulation of exposure.

"When you overexpose the resin in some areas while printing denture teeth, you are able to make the teeth more translucent toward the incisal edges," Tadros says.

These are just some of the many methods being tested, so multimaterial printing could become a reality in the not too distant future, theoretically producing restorations that require minimal post-processing steps.

"If we could print a restoration in 5 to 10 minutes with virtually no post-processing or staining and glazing required, that would be huge," Sullivan says.

Another development is 4D printinga concept in which the printed product further transforms when subjected to heat, light, moisture, or other stimuli. At least one current digital denture material leverages this concept, doubling in strength when it reaches body temperature while maintaining the elasticity of a lower-strength material.6 In addition to denture applications, the development of 4D materials could also help to unlock the vast potential of direct-printed clear aligners.

"Unquestionably, the proverbial holy grail of dental 3D printing has for many years been the direct printing of clear aligner devices," Scherer says. "The challenge is that we have a combined physics/chemistry problem. We can print super-small, and we can print super-clear, but we need to be able to print both small and clear while maintaining the physical properties that are necessary for the appliance to withstand insertion and removal on a regular basis. Generally, 3D printing materials tend to be more brittle than vacuum-formed materials. A vacuum-formed appliance is very pliable, elastomeric, and forgiving. We need to rely on our manufacturers to develop better chemistry. Whoever can make it happen will have a multibillion-dollar idea."

That capability would eliminate the time- and labor-intensive steps from the process of fabricating clear aligners. "The cost of fabricating clear aligners in-office is less than the cost of purchasing them from a third party, and you can delegate a lot of the work to an assistant or other team member, but the challenge is that it still requires a lot of work to print the models, do the suckdowns, and trim the aligners for delivery," Sullivan says. "Directly printing clear aligners would be a game changer; everybody would do it."

Further in the future, affordable metal 3D printing could open up even more possibilities. Although metal printers currently cost closer to six figures, Tadros believes that within the next 5 years, they could be available in the $15,000 to $20,000 range. "For all-on-X cases and partial dentures, the ability to print metal frameworks will be huge in terms of time savings," he says.

Renne envisions an even more advanced potential for metal printing. "We could print custom titanium implants," he says. "We could print root forms based off of each patient's anatomy. We could virtually extract a tooth via cone-beam computed tomography data and hit a button to turn it into a perfectly shaped implant. Things like that could be coming."

Will It Catch On?

Of course, a similar level of excitement once surrounded chairside milling, which has plateaued with an adoption rate of approximately 15%.7,8 Will 3D printing gain a larger foothold? Opinions vary.

Tadros estimates that, ultimately, 40% of dentists will have 3D printers in their offices. "A lot of people like myself are telling our colleagues about the benefits, and the prices will decrease," he says.

Sullivan suggests that we are already seeing it. "The biggest obstacle is the cost of entry," he says. "When you can acquire a machine that only costs $5,000 or $6,000, it becomes a viable option for many more people. Many dentists are willing to take a risk on 3D printing without necessarily knowing its full potential just because it has such a low price point."

Renne believes that cost, capabilities, and quality will continue to converge. "If a $5,000 printer can print permanent crowns, dentures, and more, then that is an entirely different situation for dentists who were on the fence about jumping onboard," he says. "As the quality improves, we will see widespread adoption."

Honey agrees about the cost factor but adds that some dentists could be deterred by many of the complexities that are involved. "There is not an easy process like CEREC® where you simply pop a milling unit and intraoral scanner into the office and everything works right away," he says. "Everything is a little more complicated and volatile with 3D printing. It is getting there, though."

The Bottom Line

In-office 3D printing might not be for everyone. Thankfully, outsourcing production still remains a viable model. As the technology improves, dental laboratories will be able to offer an even higher level of quality as well as lower fees for design and production services. However, printing in-office offers seemingly limitless possibilities.

"3D printing has the ability to impact dentistry in a very positive way, making it easier and more affordable," Ferguson says. "Getting started as soon as possible is important. As the chemistry catches up, the impact will be greater. Unless you are planning to retire soon, 3D printing will impact your practice at some point. This is the future."

References

1. 3Shape. In-office CAD/CAM is rapidly becoming a necessity. Inside Dentistry. 2009;5(8):100.

2. Nakanishi M. Profitable, high-quality digital dentures are here. Inside Dental Technology. 2020;11(2):52.

3. BEGO. The world's first hybrid material for 3D printing of permanent restorations. BEGO website. https://www.bego.com/3d-printing/materials/varseosmile-crown-plus/. Accessed May 29, 2020.

4. Brown C. The next layer. Inside Dental Technology. 2020;11(6):22-24.

5. Stapleton C. Multimaterial printing: on the horizon? Inside Dental Technology. 2020;11(6):18-20.

6. Reck C. 3D Printing in 4 dimensions. Inside Dental Technology. 2020;11(6):26-27.

7. Johannes L. Are one-day crowns worth the no wait? The Wall Street Journal website. http://www.wsj.com/articles/SB10001424127887324009304579045193833093458. Published September 2, 2013. Accessed May 29, 2020.

8. Mazda J. Trends in dentistry. Inside Dentistry. 2019;15(1):14-24.

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