Is the future of dentures digital?

February 23, 2017

Exploring the ways that technology is changing one of the oldest dental workflows.

The drawbacks of traditional, analog dentures are well known: They take a long time to make and require multiple appointments, raising your overhead. They’re prone to errors in the fabrication process and they’re inconvenient to patients. On top of all of that, they’re not even profitable for general dentists.

“In the U.S., it costs about $5 a minute to run a practice,” says Stephen Wagner, DDS, whose primary clinical investigative interests center around work simplification in removable and maxillofacial prosthodontics. “That’s an expensive overhead, and the 1950s denture technique accumulates a lot of chair time. Many dentists can’t afford to make dentures in their competitive market. The question on a lot of our minds was, “How do we shorten the denture-making technique but improve the final product?’”  

A few innovative clinicians knew the technology of digital dentistry had to impact dentures sooner or later. Many began dreaming up a simpler solution.  

Charles Goodacre, DDS, MSD, distinguished professor and previous dean at Loma Linda University School of Dentistry, imagined back in 1995 that digital files could be used in place of plaster molds to fabricate dentures. He developed an impression technique that would obtain the clinical data necessary for making a denture in just one appointment. Stephen M. Schmitt, DDS, milled early concept CAD/CAM dentures in accordance with Dr. Goodacre’s technique.

It has taken a while for digital dentures to enter the market. After a few attempts by individuals and dental companies, digital dentures have finally become a reality-although they are still in their infancy.
The digital workflow tackles the issues plaguing the traditional denture process by eliminating some of the back and forth between dental offices and laboratories. Adding digital steps to the traditional workflow alone drops the number of patient visits by about half.

Since 2007, at least six different companies have applied CAD/CAM technology to denture fabrication. In 2007, Tae Hyung Kim, DDS, a chairman of removable prosthodontics in the Division of Restorative Science, Ostrow School of Dentistry, USC, joined six other dentists to come up with the concept behind DENTCA digital dentures. A patent was filed on the technology in 2009 and the dentures were on the market in 2012.

The AvaDent Digital Denture was created in 2011 by Global Dental Science and became available for use in 2015. That spring, both the Wieland Digital Denture from Ivoclar Vivadent and the PALA Digital Denture System from Heraeus Kulzer entered the market. Canadian company Perfit Dental Solutions introduced their digital denture in 2017. And finally, Glidewell Labs has a “digital spin” on a traditional denture.

Companies are also creating denture design modules as add-ons in their CAD software. At this point, the software offers the ability to print or mill digital dentures. Examples include 3Shape Dental System 2015 Denture Design and Dental Wings DWOS Full Dentures. Exocad is also launching a denture module for their DentalCAD software.
DENTCA, Wieland and PALA all allow impressions and bite registries to be taken in one step with their proprietary impression trays. That information is then transferred to design software. AvaDent also offers their own impression techniques, though they can use the clinical data from any impression system, so long as these six key values are defined, including the vertical dimension and the incisal point.

(It’s helpful to point out here that some-though not all-of the experts interviewed in this article have an affiliation with AvaDent. Therefore, many of the examples of the digital denture workflow will be based on that technology.)

Impressions can then be scanned and turned into a digital file to send to the milling facility, or they can be physically mailed in. Once the digital files are created, a virtual 3D image of the denture is available to the dentist for tweaking. They can either print or mill a try-in, or they can go straight to the final prosthesis. The total number of appointments for digital dentures can be as few as two (or three with a try-in).

Glidewell’s process looks more traditional, while Perfit’s looks a bit different than how it’s been done. That digital “spin” Glidewell references is the ability to scan a stone model into the design software. Compared to the other digital systems above, that requires an extra step beyond the traditional impression. It’s done by the laboratory once they’ve received the initial impression (as opposed to receiving a digital file). Perfit is unique in that it relies on a 3D intraoral scan for the clinical data.

“Most of the digital dentures are traditional dentures with digital workflows,” says Dr. Wagner, who argues that the AvaDent denture is the only true digital denture available. “There are two components to the digital denture workflow: the final product and digitally augmented clinical steps.”

“For the last three years, denture fabrication has become exclusively digital,” says Stephen F. Balshi, MBE, president of CM Prosthetics laboratory. “Prior to that, some were digital and some were traditional, depending on the patient circumstances.”

Up next: Advantages of digital dentures ...

 

Stephen Balshi started working with AvaDent shortly before the introduction of their digital denture. He was impressed with their work in dental implants and dental implant prostheses and now appreciates the shorter workflow and consistent quality esthetics.

“The dentist makes the clinical records and fills out a prescription to me in the lab, and I digitize those records and submit them to AvaDent for digital design,” he says. “In the lab, I can modify the design. I send the link to the dentist for review, and once it’s approved, I authorize AvaDent to mill it on my behalf. Most of the time, the denture can be delivered in two visits.”

“We no longer have to do the try-ins because we know what the arrangement can be on the computer,” says Thomas J. Balshi, DDS, PhD, FACP, co-author of “A Patient’s Guide to Dental Implants” and contributing author to “Dental Implants: The Art and Science (2nd ed.)” and “Zygomatic Implants: The Anatomy-Guided Approach.” (Stephen Balshi is Dr. Balshi’s son.)

“The master impression can be made during the first visit. If they’re wearing a traditional denture and they need a new one, we can simply take a wash impression in the patient’s denture and scan it while they’re waiting. If you have to send something out, you can make a duplicate denture and take the master impression and the occlusal registration and send that off to the lab for scanning.”

“It allows us to provide a denture to a person in two to three appointments instead of the typical five,” Dr. Goodacre says. “Besides the obvious convenience of it for patients, you can create more cost-effective dentures.”
Digital dentures leave room for the traditional process as well. A dentist can go digital after the initial impression, or they can choose to keep the traditional workflow, adding in the digital aspect by designing and milling the final prosthesis from the digital software.

“They want to make sure dentists were comfortable doing it either way,” Dr. Wagner says. “Maybe a dentist doesn’t want to use our technique: they’re comfortable with the old method and five appointments doesn’t bother them. They can still end up with a superior digital denture, but they could also avail themselves of these newer time-saving techniques.”

A fully digital process would start with an intraoral scan of hard and soft tissue. However, because the perfect fit depends on accurately measuring the soft tissue of the mouth, that process would be ineffective.

“Every time you put the wand inside someone’s mouth, you’re moving soft tissue and everything is changing,” Stephen Balshi says. “It would be nice to find a way to remove functional impressions, whether that’s with an MRI or some scan we don’t know about yet. But for now, it’s extremely accurate and we get tremendous results.”
The technology isn’t available yet that would facilitate an entirely digital denture process. But things are progressing rapidly.

Read more: Why companies are offering a digital try-in ...

 

Digital try-ins

All of the digital denture companies offer a try-in, but whether that’s for the benefit of the patient or the dentist is uncertain. AvaDent claims that defining those six values is the “holy grail” that produces a perfect denture the first time, but many dentists still find a try-in reassuring, at least at the beginning.

“Originally, most digital dentures were advertising themselves as a two-appointment technique,” Dr. Wagner says. “But there was a component missing: trying the teeth in to make sure everything is correct.”

“There’s a learning curve for both practitioners and technicians,” Stephen Balshi says. “It’s natural for a first-time user of any technology to want to do a try-in. Being able to conceptualize virtually compared to what they see clinically is a big leap.”

Foreseeing that difficulty, Dr. Goodacre created a prototype CAD program for dental students in 2009. The 3D Tooth Arrangement Program was used in 2010 at Loma Linda University School of Dentistry “to teach students how to arrange teeth virtually before performing the actual laboratory procedure.”

“The only downside [to using digital dentures] is making a change and being able to visualize the final denture,” Dr. Goodacre says. “It’s certainly doable, and for the younger generation, it’s an easy step for them. Adaptable dentists might make two to three dentures and then be perfectly comfortable. It’s pretty easy to sort out, generally speaking.”
After the first time, the number of dentists who choose to do a try-in for a new denture seems to decrease.

“I would put the denture in the patient’s mouth and sit down with a handpiece getting ready to adjust the bite,” Dr. Balshi notes. “It took me a while to look in there and think, ‘Whoa, if I adjust this, I’m only going to make it worse because this is as good as it gets.’”

But there are still plenty of situations in which a denture try-in is still essential.

“Occasionally we do a try-in when we’re making a significant change or a first-time denture,” Dr. Balshi says. “Unlike a wax try-in that produces the esthetic appearance, these are functional try-ins. The patient could wear it home to test it out.”

“Another type of try-in allows the practitioner to move the teeth around in a thermoplastic resin,” Stephen Balshi observes. “It’s a little more traditional in that teeth can be moved around because it’s temperature sensitive. It’s not a fully functional try-in; it’s more of an esthetic try-in.”

Two or three appointments is the norm so far, but Dr. Wagner had been utilizing a faster approach long before he teamed up with AvaDent.

“As a maxillofacial prosthodontist, I’d been doing a three-appointment denture in my practice for years,” he says. “I did that in two ways: one was to develop a new way of making impressions that eliminated that preliminary impression and custom tray. Then I developed techniques where I could pre-set most of the teeth prior to trying them in the patient’s mouth. When I saw that AvaDent was making a digital denture, I approached them and said the two-appointment technique wasn’t viable, because there were too many potential errors.”

Up next: Milling digital dentures ...

 

Milling

DENTCA, AvaDent, Wieland and PALA use CAD/CAM technology to mill final dentures, although the prototypes used for try-ins can be printed, since they’re not intended for long-term use. (Available printing materials aren’t yet strong enough for daily denture wear.) Ultimately, the final prostheses are milled before adding the denture teeth.

The AvaDent denture is unique in this matter. It is milled from one piece of material, making it kind of a monolithic mystery.

“I recently gave a talk and was trying to demonstrate the differences between two AvaDent dentures: one that was made with AvaDent’s traditional technique of milling from the same material, and one in which the teeth were milled separately,” Dr. Wagner says. “I couldn’t tell them apart, almost to my embarrassment.”

The monolithic process is said to make it both more esthetically pleasing and hygienic.

“Traditionally, denture resin is squeezed and compressed under a couple of hundred pounds,” Dr. Wagner explains. “AvaDent puts the resin under 40,000 pounds of pressure. It is denser and much less permeable to bacteria, making it more biocompatible.”

While most companies use CAD/CAM, AvaDent offers computer-aided engineering (CAE) to produce dentures in a digital workflow. “Think of it as CAE being the brains to CAD/CAM’s brawn,” the company writes on their website.

“The AvaDent line can also be used for final prostheses for implant patients,” Dr. Balshi notes. “You can have a fully milled titanium framework with a monolithic denture or an Accelerset Prosthesis: The first section is pink resin for the gingiva, the second is a block of titanium to fit on the implant and support the gingiva, and the third is a block of ceramic material for crowns, which will be milled onto the framework. All three are milled at the same time off the same file system for that individual patient.”

Labs

The denture modules available through Exocad, 3Shape and Dental Wings offer chairside printing or milling. The other four mill the denture in their respective facilities, though there is the potential for crown-and-bridge labs to add digital dentures to their workflow.

“For the high-end proprietary dentures, you have to send [the AvaDent data] to the GDS lab,” Dr. Wagner says. “But they’re developing techniques where a local lab can mill the base. That will be available to dental labs in the first quarter of 2017.”

This news, announced last October, is a result of the recent alliance between Dentsply Sirona and AvaDent.

“Now that Dentsply [Sirona] and GDS have merged in effort, they’re going to start offering milled denture techniques for labs,” Dr. Wagner observes. “With Dentsply [Sirona]’s software and design help, they can now make dentures in their own laboratory.”

Having the ability to send files to a milling facility is already changing laboratories, according to Stephen Balshi.
“It’s completely changed my lab,” he says. “It’s quite rare now to set denture teeth traditionally, and the inventory of denture teeth in the laboratory is going down because it’s not necessary to maintain those different molds and shades.”

Dr. Wagner agrees that the changes are positive.

“AvaDent’s final denture is better than I can make in my own lab, and in the last year, it has become superior to anything that’s been made before,” he says.

Read more: The learning curve ...

 

The learning curve

Although digital dentures offer a multitude of benefits for everyone from the patient to the lab owner, there is a learning curve.

“Dentists are going to have to learn a new technique and be digitally inclined,” Dr. Goodacre says. “You have to learn how to look at something virtually instead of holding it in your hand as it’s done in a traditional process.”

“The clinician has to embrace living in a modern world,” Dr. Balshi says. “We have digital medicine all over-robotic surgery is being done, catheterizations are being done digitally-so why shouldn’t the dental profession embrace the digital technology that’s out there?”

The learning curve is minimal, however. Even dentists who had previously held out on going digital in their practice have made the transition.

“I didn’t have digital systems at all,” Dr. Wagner says. “I’d been doing it for 40 years, so I had my way of doing it. I was happy with my process, but then I realized that this technique was much better than analog.”

The need for digital dentures

Going digital with dentures is not just a marketing ploy to get dentists excited. It’s here to stay not out of convenience, but out of necessity.

“It’s very difficult to find high-quality removable denture technicians,” Stephen Balshi notes. “Many of them are getting older and retiring and they’re not being replaced with younger technicians with the same ability; they’re being replaced by computers and people who know how to use computers. It’s happening, and it’s a good thing that it’s happening because the profession needs it to continue.

“There is a reduced number of quality technicians coming into the workforce and the number of schools for dental technicians have decreased because it’s not a desired profession. Applying the digital world to that industry and bringing in the new generation of people who can be taught dental fundamentals and apply their virtual mindset to whatever-digital dentures, single crowns-is a necessity.”

Dental school curricula

In the meantime, many dentists see digital denture technology changing the industry on a wider scale.

“The fees that a general dentist can get for a denture are competitive from city to city,” Dr. Wagner says. “There are people who make low-cost dentures. They’re not very good but the fees are low. Specialists make expensive dentures. The general dentist is in the middle, and they have to work at a competitive price. They learned they couldn’t profit so they stopped making them.”

Because dentures are done by specialists, dental schools have placed less emphasis on denture training, further exacerbating the issue.

“The other part is that millions of patients need dentures,” Dr. Wagner notes. “Young dentists don’t feel comfortable handling dentures because they didn’t make many in dental school. Even worse, the technique they learned wouldn’t earn them a profit. I feel that promoting a three-appointment technique will allow them to make a consistent, high quality, simplified denture, and they could then provide dentures for their patients and grow their practice. I’ve been on a mission for the last decade saying that we’ve got to make better techniques for those dentists that should be providing dentures that don’t. That’s kind of what we’re seeing.”

Dental schools are now making changes to their curricula in order to include digital denture training.

“I never thought an undergraduate dental program would ever change, but I’ve had seven dental schools call me already,” Dr. Wagner says. “They’re talking about changing their undergraduate program fundamentally. Administrators are getting a sense that the technology is advancing in the country.”

“The progressive schools are going to incorporate this into their curriculum so students will be in the position to provide the conventional and digital processes of making a denture,” Dr. Goodacre believes. “When the digital denture becomes the major way, the students won’t have to be re-educated. They’ll already know how to do it.”

Up next: Improving digital dentures ...

 

Potential improvements

When the iPod first became available in 2001, there weren’t many people who lamented the weird circular scroll bar or the comparably terrible graphics. Consumers didn’t complain about the small screen or the weight of the device. Instead, users were impressed and obsessed with the technology. Suddenly, a portable music library that could hold thousands of songs in your back pocket became the norm. Had someone asked anyone what they would change if they could, no one would have described the iPhone of today (or 10 years from now).

That’s kind of how experts feel about today’s digital denture workflow.

“It’ll just be refinements in the ways in which you can make the records: obtaining the information you need for the denture and improving the fabrication process and the speed and volume with which it can be done,” Dr. Goodacre explains. “All of those will lead to improvements in quality and cost, which can be transferred to the public.”

“This technique that we’ve developed is Generation One,” Dr. Wagner says. “Materials aren’t going to change radically. It’s more about technique. It’ll be more of an evolution.”

Nobody is certain what the second generation will look like, but there is one common request: Eliminate the functional impression.

“I think the holy grail of the process will be when we can digitally take the impressions,” says John Flucke, DDS, and chief technology editor for Dental Products Report. “That’s really been the whole idea of digital impressions for crowns and bridges, but the mouth is not static, and that can greatly affect the denture fit. They might be able to get to a point where there is some kind of camera that can take images of the mouth and identify where the edge of the denture should be. I can see that being worked out in the not-too-distant future.”

As general dentists practicing in the U.S. are able to add digital dentures to their repertoire, the tide will rise and lift all boats. The burden of 178 million edentulous patients on prosthodontists will be lessened, patients will have greater access to quality, affordable care, and dentures will become profitable for the general dentist.

“It’s growing rapidly, and it’s going to change the whole paradigm by which dentures and denture teeth are made,” Dr. Goodacre says. “It’s a true paradigm shift in removable prosthodontics.”

“I think we’re in the denture-making renaissance,” says Dr. Wagner. “People are respecting dentures more. We are understanding that patients need them and they need to match the quality of the finest bridge work. As soon as dentists learn they can make dentures more effectively and with more confidence, that will be the game-changer.”