The biggest evolution in dentures is almost here

October 22, 2018

Article

With digital dentistry taking the industry by storm, the future of dentures is looking bright.

Dentures have been replacing human teeth for thousands of years. In the last 80 years, we’ve seen them evolve at a rapid pace. However, with digital dentistry poised to tackle removable full and partial dentures, we might be on the cusp of the most significant evolution in dentures since humans started mounting false teeth in Vulcanite back in the 19th century.

A brief history of dentures

Per the History of Dentistry, the earliest dentures were thought to date back to 2500 BC. Found in Mexico, these early dentures were made from the teeth of wolves. In Italy, evidence of dentures made from gold wire and human and animal teeth were found dating back to 700 BC. Archaeologists also found two false teeth made of bone and wrapped in gold wire in a tomb in ancient Egypt.

Dental materials didn’t change much in the early days of dentures. Using human teeth pulled from both the dead and living, along with animal teeth, were the first choice for early denturists. The first wooden dentures appeared in Japan in the 16th century, and they were used there until the early 20th century.

Denturists began to explore other denture materials in the 1700s, including ivory from rhinos, hippos and elephants, and using teeth from cadavers and animals. Ivory remained the popular denture base material for the next 100 years - but only for the wealthiest patients.

One wealthy recipient of early dentures was former U.S. President George Washington. However, contrary to popular belief, his teeth weren’t made of wood. The base was lead and the teeth were a combination of horse, donkey and human. One of the interesting features was the springs that retained the dentures. President Washington would have had to clench his jaw to keep his mouth closed when he wasn’t eating or speaking.

One of the foremost contributors to the evolution of denture materials was sugar. The wealthy were losing their teeth quickly as their consumption of sugar rose. Since no restorative dentistry existed in those days, these wealthy dental patients had their teeth pulled and needed replacement teeth.

There was some experimentation with porcelain teeth in the late 1700s, but extracted human teeth were the preferred replacements. Patients liked them because of their durability and effectiveness for eating.

In 1815, per the BBC, “Waterloo teeth,” which were teeth pulled from the tens of thousands of soldiers who died in the Battle of Waterloo, were popular and mounted in a base made from animal ivory. Dental technicians at the time would boil the teeth, chop off the roots, and then attach them onto ivory bases. The dentures were held in place by springs, like those used in President Washington’s prosthesis.

Other sources for human replacement teeth were grave robbers. However, live donors would also sell their teeth for wealthy people’s dentures. Usually the poorest of the poor, the live donors would have their teeth yanked for money - without anesthesia, of course.

Dr. Shirin Khoynezhad, director of second-year pre-clinical dentistry at the University of Alabama, is a prosthodontist who lectures on denture materials and CAD/CAM dentures. She compared the process of selling your teeth to organ donation.

“A lot of slaves or people who needed money used to sell their teeth for making dentures for the wealthy. It was very high-end dentistry to have a denture in those days, a luxury,” Dr. Khoynezhad says.

Continue to page two to read more...

By the mid-19th century, porcelain teeth replaced human teeth in dentures, and Vulcanite, a flexible rubber compound, replaced ivory. Per the British Dental Association, Charles Goodyear discovered how to make Vulcanite from India Rubber (also known as caoutchouc) in 1843.

A few years later in 1854, the first Vulcanite denture was made. Vulcanite became the preferred denture base. It could mold to the patient’s gums and palate. After curing the Vulcanite and adding the porcelain teeth, the upper denture used suction cups to self-retain, which made springs unnecessary.

Patients liked that Vulcanite was more durable and lightweight than ivory. Perhaps most importantly, however, Vulcanite was affordable and made dentures available to people other than those of the wealthiest classes.

The process was patented and sold to the Goodyear Dental Vulcanite Company. The company sold licenses so that dentists could make a Vulcanite denture. However, the licensing fee was highly unpopular with the dental community, and it led to some experimentation with other dental materials that weren’t subject to a license fee. Some of these alternative materials were successful but faded from use after the license expired on the patent for the Vulcanite denture process in 1881.

Vulcanite wasn’t perfect though. The finished product was dark red and didn’t look natural in patients’ mouths. To get the color pink on the gum section of the denture, the technician would affix a pink-colored piece of porcelain to the Vulcanite base. It was also smelly and hard to process.

Porcelain teeth had problems, too. Early porcelain teeth would chip easily. Dan Elfring, CDT and in-house technician for Pickle Prosthodontics in Colorado Springs, Colorado, says they were also hard to grind and noisy. “They clack and make a lot of noise,” he says.

Despite these shortcomings of both Vulcanite and porcelain and the unpopular licensing fees, Vulcanite dentures with porcelain teeth were the preferred material for nearly 75 years.

Continue to page three to read more...

Dentures in the 20th century

The 20th century was the plastic era for dentures. Experiments in plastics began in the second half of the 19th century, but none proved to be better than Vulcanite dentures.

In 1909, Dr. Leo Bakeland introduced Bakelite, a phenol-formaldehyde resin. It was easy to get, but it wasn’t uniform enough, it was challenging to mend and it had color problems. However, Bakelite paved the way for further experimentations in plastic dental base materials, resulting in more successful plastics later on.

The introduction of methyl methacrylate in 1937 as an “ideal denture base material” changed everything. By 1946, some experts estimated that 95 percent of dentures were made with methyl methacrylate polymers (PMMA). At first, PMMA resins were heat-cured, but by 1947, dentists in Germany were curing the materials using chemical acceleration. This process was the beginning of self-cure resins.

PMMA produced a superior denture to Vulcanite. It yielded better esthetics because of its translucent property. It was also harder than Vulcanite and didn’t have a bad smell or toxic property. PMMA is easy to fix and affordable. For all of these reasons, PMMA continues to be a popular denture base material even today.

“For the greater part of 100 years, dentures haven’t really changed that much, both full dentures and partial dentures. The commonplace method of constructing with a full denture is out of acrylic plastic, and the method of making a partial denture is from a chrome-cobalt alloy,” says Justin Marks, CDT and founder and CEO of Arfona.

Marks says there have been incremental changes in dentures over the past 80 years but that the method and technique have largely remained the same.

When Elfring started as a dental technician 40 years ago, he remembers “old-timers” talking about Vulcanite dentures. By the 1970s, however, most denture bases had transitioned to PMMA materials. The tooth materials had also made a transition to PMMA resins, which provided many benefits to both the technician and the patient.

“They [denturists] were starting to work different shades to get different layers and improve the esthetics of the teeth. PMMA teeth had advantages because you could grind on them and they would bond to the denture base material better than porcelain,” Elfring explains.

That said, acrylic resins aren’t perfect. Dr. Khoynezhad notes that when you process acrylics, they shrink. When dentures don’t fit properly, they create sore spots for patients. Also, the pores inherent in acrylics can gather microorganisms, which can result in bad odors, color changes and inflammation in the patient’s mouth.

“Besides that, there is also residual monomer, and while it is a limited number of people, some patients are sensitive to that,” Dr. Khoynezhad explains, adding that she would like to see more development that improve acrylics to address these problems.

Meanwhile, teeth materials evolved from PMMA to PMMA and composite. The composite added a durable surface to the tooth, which Elfring says is better for wear but worse for bonding. However, providing the composite and PMMA in layers allows there to be a PMMA layer that provides a bonding surface.

“There are pros and cons,” Elfring says. “You have to choose your materials based on what you are trying to accomplish. Choosing the right materials is a big deal.”

Continue to page four to read more...

Dentures in the 21^st century

It’s an exciting time for dentures today. Elfring says the end products are improving drastically from before, a sentiment echoed by Dr. Khoynezhad.

“Material-wise we are still dealing with the same PMMAs, but technique-wise we learned to work with those materials better to deliver more accurate care for our patients. We have fewer errors and less shrinkage and volumetric changes,” Dr. Khoynezhad says.

Marks agrees, adding that right now we’re experiencing the most significant evolution in dentures in the past 100 years.

“The paradigm shift only started in the past five years, and it’s about to explode in the next five, partly because the materials and the techniques themselves are becoming more refined and partly because of the penetration of digital equipment in the industry,” Marks says.

The latest denture evolution is CAD/CAM and 3D printing. Dr. Khoynezhad suggests that this latest evolution brings dentures to another level regarding patient comfort, quality of care and quality of the dentures themselves. In addition, it shortens the time it takes to produce a denture.

Elfring says the puck material used to mill the denture base is strong, pressed seven to 10 times the pressure of an Ivocap^®-injected denture. While 3D printing isn’t as strong or dense as a milled base, it’s faster, easier and more economical to produce.

Another driving factor for change, Marks says, is that many experienced denture technicians are retiring in the next five to 10 years. Because of that, dentists will need alternative methods of denture production to replace this aging workforce, especially as the Baby Boomer generation ages and their oral health declines.

“There is an influx of work to do, and the labor pool is drying up,” Marks says. “It’s the perfect storm of events for new technology to be able to address that market influx.”

With much of the 21st century still before us, the future of dentures could go many different ways. Marks thinks that digital dentistry will become the preferred method for fabricating dentures and the increased demand for dentures with a decreased labor pool will push the technology forward.

“We need to make more dentures with fewer technicians and digital can do that. The population that requires dentures now is already underserved,” Marks says.

Some dentists avoid dentures because of the extended delivery timeline and chair time involved, along with all of the adjustments and repairs. Marks believes that digital dentistry will improve the denture delivery process by reducing chair time and requiring fewer appointments. However, it will still need lots of help from a denture technician.

“It’s important for the dentist to know when we talk about 3D printing, they shouldn’t expect to run out tomorrow, buy a 3D printer, and all of sudden cut out their lab because everything is going to be coming out of the snazzy new box that they just bought. It still requires interaction with a dental laboratory and the expertise of the denture technician,” Marks says. “It would just be that the tools and format through which we do that is changed.”

Dr. Khoynezhad believes that in addition to developing better acrylic resins that address some of the problems with the present materials, scanners will also improve in the 21st century to capture the muscles around the denture bearing areas intraorally. Currently, traditional impressions are used to capture the soft tissue surrounding the denture.

“I would think that the next evolution would be some wearable scanner that can record the function of the muscles accurately and can be transferred to the software to generate virtual casts and, after denture design and virtual teeth set up, will be sent to milling machines where they design and build the denture out of it. That’s my sci-fi vision for dentures of the future,” Dr. Khoynezhad says.