What you need to know about the evolution of dentures

Dentures are, certainly, nothing new. They have been around in some form or another for almost 3,000 years. For much of that time, denturists used human or animal teeth to give edentulous patients the chance to chew again. And while that may sound uncivilized in this day and age, the fact remains they were the best materials for the job.

Materials and processes have most certainly evolved – especially in the last century. In fact, laboratory technicians have seen the biggest development in the past two decades. As such, those same technicians have had to change the way in which they work.

A time of change

“Both dentures – full and partial – have been fabricated the same way for the last hundred years,” Justin Marks, CDT, founder and CEO of 3D printer manufacturer, Arfona, says. “You take prefabricated denture teeth and arrange them in wax, on a box or model, and that wax-up would be covered with more plaster inside a flask. That process called ‘lost wax casting’. The denture would be either injection molded or pressure packed with acrylic polymer, or in the case of a partial denture, the wax would be burned out or evaporated in the high temperature furnace, and then cast in metal alloy. Both of those procedures, whether it be full dentures or partial dentures, didn’t really change all that much for the greater part of a hundred years.”

In the 21^st century, CAD/CAM changed all that, but not immediately so. Technicians, like Marks, tend to adopt a digital workflow incrementally.

“I started to experiment with CAD/CAM going back about 10 years, maybe a little more,” Marks remembers. “At the time, digital full dentures hadn’t really been invented yet.

Digital partial dentures were starting to make their way into the marketplace. But it was really limited to being able to do a digital design on a screen, print out a resin pattern, and then you would cast that in metal using old-fashioned techniques. A few years after that, you were able to design dentures, digitally, because the software caught up, but the manufacturing techniques really hadn’t. For both dentures and partials, the first CAD/CAM systems were: You could design it and look at it on a screen, but you couldn’t actually take it off the screen and turn it into a tangible object. That really has been more in the last five years that we have actually brought digital dentures to fruition, and not just with 3D printing, but even milling, before that. There are ways to actually produce that now, as a tangible item.”

Workflows

While CAD/CAM is certainly gaining in prevalence, not everyone has jumped ship from the analog workflow. Technicians like Dan Elfring still rely on those traditional, analog methods.

Elfring has been a dental lab technician for four decades – the first 28 years in the Air Force and for the past 12 as an in-house lab technician at Pickle Prosthodontics in Colorado Springs, Colorado.

Even though that workflow has been more or less the same for the past hundred years, it has evolved. The dentures that Elfring makes now are different than the ones he made at the beginning of his career.

 “A lot has changed over the years, especially in the way of dental materials, equipment and processing,” Elfring says. “Before I was press packing and heat curing, and then I went to Ivocap, which is injected processing. Now I’m currently using IvoBase, which is continuous injection. The acrylic is cured much differently and I’m using better acrylics, better material, and better teeth.”

Change is a good thing, and the results are evident in better prostheses.

“Denture bases are denture bases, teeth are teeth, if you will, but the way I inject or process the acrylic has really changed,” Elfring says. “We feel we can get a better end product, and because so much of our work is hybrid work, which means it’s fixed-removable, it’s all-on-four fixed hybrid, so it’s dentures that are implant-retained and screwed into the mouth. We get a better, denser acrylic by injecting it, versus press packing it and heat curing it. Because we are a high-end practice, we want to use the best materials and processes we can. It fits well with our workload to try and improve the process. We’re not a high-production laboratory to where we’re looking at, ‘How can we do it faster and cheaper?’ We are more customized and we are looking at, ‘How can we do it better?’”

Enter CAD/CAM

While the industry tends to look to the digital nature of CAD/CAM as the next, greatest step in dentures’ evolution, it is not without its limitations. Especially when it was first introduced, there were some aspects of CAD/CAM that just didn’t live up to the hype.

“There were two manufacturing challenges,” Marks says. “One had to do with the materials, themselves, either being developed or going through the regulatory process. There were materials that were under development at the time, or even market-ready, but they still had to go through the regulatory process of FDA and all of the foreign governments that they are exported to. The other factor was economic. Just because it’s such a paradigm shift moving from making things by hand to making them digitally that the types of products that were being sold and needed to be purchased by laboratories have changed.

"Now, all the large manufacturers that make denture acrylics and denture teeth, they wanted to find a revenue model that was going to suit them. Because, all of a sudden, if you’re not buying pre-made denture teeth anymore, if you can make a tooth either from 3D printing or from the milling process, then all the manufacturers who had been supporting denture teeth, they need to find a way to get some skin in the game. I would mention both of those as, not drawbacks, but reasons that the adoption rate was a little slow, initially. Now that some of those challenges have been overcome, digital dentures are at the forefront of everything we talk about, nowadays. I think they’re really going to become extremely pervasive in the next five to 10 years.”

Elfring is not standing still. While his work is still rooted in the analog workflow, he is considering a foray into digital dentistry, but incrementally so.

“Our first step would probably be to buy a lab scanner,” Elfring says. “And there’s a lot we can do to design our titanium bars. We do a lot of titanium bars, and if we could cut our costs in half and also use the scanner to scan models and design dentures, then we could use it to get into the digital dentures. There are various steps that we could use in printing things like intraoral scans, bites, radiographic guide stents, and bone reduction guides.”

Learning a new skill set

There is, obviously, a new skill set for technicians venturing into the digital workflow, and for some, it might be daunting.

“In some regards, that has been challenging, and in some regards, it’s been relatively easy,” Marks says. “The way in which we communicate now, digitally, makes it easier to teach these techniques. The educational opportunities are more widespread. But, at the same time, technicians who have been trained in traditional ways and have, up until now, had no exposure or experience with CAD/CAM, they are at a slight disadvantage over technicians that have. And I say that because technicians who already are exposed to CAD/CAM and have experience with it, even if they’re not skilled in removable prosthetics, whether it be full dentures or partial dentures, they understand the tools, they understand the software at this point.

“So, it’s a small step for them to learn the background of how to fabricate or design a removable prosthetic, and I would say they have an advantage over a technician who is slow to even use a computer. From my own experience, my lab used to be a much larger service bureau. We did both metal frameworks and Valplast dentures for other labs, and I can’t tell you the number of other labs that I used to work with that didn’t even use email – that’s going back five years. So, it’s going to be tough for them if they haven’t already adapted, just the way we communicate, to totally change the way they work in the laboratory with digital tools.”

Getting into the digital workflow can be intimidating, especially as it seems to change on a seemingly daily basis.

“Especially because of how quickly it’s developing,” Elfring says. “Five years ago, if you wanted to buy a scanner, you might have three options. And if you consider A, B and C, the decision point might be very specific. But now there’s getting to be so many scanners and so many software options, that the decision making has been exponential. Then, because of the growth of the industry, what I hear is one of the major problems is customer support in the software line. If you’re new to digital and you don’t know what to do, and you buy the thing and don’t get support, then that becomes a concern. There are definitely concerns about buying the right equipment from the right people to get decent support when you have a problem.”

In some regards, technicians who are just coming out of school have a leg up on technicians who have been working in the field for decades. That is, they have been exposed to computers their entire lives, and are even trained in digital dentistry in school.

“I teach it as an adjunct at New York City College of Technology,” Marks says. “We have the largest dental technology program in the country. We are also the first college to offer a full-time CAD/CAM course in the fourth semester for our students. I do believe that some other colleges have followed suit since. Even though we offer a separate CAD/CAM course, as an elective, we are now looking at ways to also bring digital into some of the other core courses of the curriculum, including dentures and partial dentures. Even if I don’t have my students do it in the semester, I teach the partial dentures course there, and, at a minimum, I will still give them demonstrations and show them examples of how digital is used to make dentures.”

3D printing

CAD/CAM is a far cry from the human and animal teeth used to craft dentures 3,000 years ago. The latest iteration of CAD/CAM is possibly the most exciting – 3D printing. Rather than mill the CAD/CAM-created dentures, the appliances are sent to a 3D printer.

Arfona sells 3D printers that can be used to print dentures. Before that, he worked for Valplast Corporation, a manufacturer of flexible nylon for partial dentures.

“We had researched and developed, over the course of about 10 years, a method for 3D printing flexible partial dentures,” Marks says.  “Arfona is really a spin-off of the work we were doing at Valplast.

“The majority of cases that I do are partial dentures, and the majority of them still come from traditional impressions,” he continues. “Dentists either send us physical impressions or models. We digitize that as soon as it gets to the lab. We will either scan the model, or in a lot of cases, even scan the impression, and not have to pour a model, because that will be done digitally, and then we’ll fabricate the appliance, whether it’s a denture or a partial, digitally. All of our Valplast partials are 3D printed, and the teeth get custom-made through a milling process. All of our full dentures are milled through a subtractive manufacturing process. The full digital implementation has been in the last six months. I have not made a traditional denture or Valplast partial in the last six months.”

Everything evolves over time. Even though something might seem “good enough”, there will always be room for improvement. And while the 3D printed, CAD/CAM-designed dentures of the 21^st century are a huge leap over the animal teeth dentures of 700 BC, there will almost certainly be better materials, processes and tools in the years to come.