IEEE PULSE presents

New Dental Tech Says a Mouthful

Feature July/August 2015
Author: Leslie Mertz

Above: Dentistry has evolved considerably, first with digital dental radiography, then cone beam computed tomography, and now intraoral scanning, which includes scans made with lasers, a series of LED lights, or high-speed video imaging, according to Jonathan Ferencz. Here, he uses the Color Trios Scanner (3Shape) to perform an intra-oral scan. Photo by Pasquale Fanetti.
Not so long ago—in some cases a matter of just a few years—patients could scan the dentist’s office and understand what they saw: a tray of poking tools, a suction device, a spitting bowl, possibly the articulating arm of an x-ray machine, and other easily identifiable instruments.
But today’s dentist’s offices are getting a new look, thanks to digital technologies that are designed to provide better oral care. This includes next-generation radiography, digital scanners, computer-aided design and manufacturing (CAD/CAM) systems, and a selection of new materials.
A number of factors (see “Making the Leap”) will determine how quickly any particular office adopts the new technology, but experts believe it is just a matter of time before nearly every dental procedure will be updated to incorporate digital components.
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The dental field is a bit slow to embrace new digital technologies for several reasons, but the two most notable are training and costs.
Dental schools seem like a good place to start for training, but it’s more complicated than it may seem, says Lyndon Cooper, director of the prosthodontics graduate program at the University of North Carolina. At present, schools are grappling with a possible curriculum overhaul. “We are looking ourselves in the mirror and asking, ‘Are the old techniques we have been teaching valid today?’ For example, schools may offer a dental-materials class that spends weeks teaching about the physical properties of laboratory plaster and wax, acrylic resins, and polymers, but they may not teach computer science and what an STL file or an OBJ file is, or how a software program delivers this to a CAD/CAM mill.” That has led dental school to confront the potential of a major revision in how they teach.
Such a curriculum shift would include the addition of lots of expensive equipment. “Scanners can cost $20,000-$50,000, and mills can run between $30,000 and $150,000. So if you need to outfit a group of 100-200 dental students, you’re looking at million-dollar investments,” Cooper says. On top of that, equipment can become obsolete in a matter of a few years, which would lead to regular and also expensive upgrades. In answer, he says, dental schools are beginning to think about other educational avenues, including joining together to create multi-school centers where students can share equipment.
While the schools consider their options, individual dental practices are facing their own struggles. “Dentists are now faced with moving their practice models from businesses where they bought commodities, such as impression material or retraction cord and stone, on a monthly basis to capital-equipment models where after two or three years, they have to look at tens of thousands of dollars of investment in hardware and software just to remain current,” Cooper describes.
This new model may favor group practices over solo practices, he says, because a piece of equipment that is economically viable for a group of four or five dentists, may simply be untenable for a single practitioner. The other option is for a practice to use a state-of-the-art dental laboratory as a conduit to the digital workflow, he says. “This represents a remarkable opportunity for dentists to be engaged. Of course, this requires the dental laboratory field to also be fully engaged and ready to adopt these technologies, and fortunately, many of the most talented technicians in our country have fully embraced digital as a better way of working.”
As individual practices and dental schools weigh their options, one thing is certain: Digital technologies will continue to propel the field of dentistry forward, Cooper says. Change is coming, and even if it takes a while, schools and dentists will eventually adapt.
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Seeing in 3D

One of the earliest upgrades came with the availability of digital dental radiography, designed to replace analog, film-based x-rays. Digital radiography, which started to appear in dental offices about two decades ago, not only reduced the patient’s exposure to ionizing radiation, but also allowed the dentist to see the image instantly and share that image with a colleague anywhere in the world via the Internet.
More recently, cone beam computed tomography (CT) took radiography to a new level, generating images of bone and soft tissue, says Jonathan Ferencz, scientific chair of the first International Symposium on Digital Dentistry held in Florida last fall. He is also clinical professor of prosthodontics at New York University College of Dentistry, adjunct professor of restorative dentistry at the University of Pennsylvania, and a practicing prosthodontist (see top featured image). The cone beam CT rotates around the patient, capturing data in three dimensions using a cone-shaped X-ray beam. While not routinely used for typical office visits, this technology is becoming more commonplace for gathering information to help plan implant surgeries and placements, and certain root canals. “We used to have to send patients to hospital-based x-ray centers to get 3D x-rays taken, but cone beam CT machines are now small enough to be used in a dentist’s office,” he says.
Digital views of the patient have now expanded even further to intraoral scanning, a broad term that includes scans made with lasers, a series of LED lights, or high-speed video imaging. Like most other electronics, their scanners’ performance has increased while their size has decreased, Ferencz said. “For example, I was at the International Dental Show in Germany in March 2015, and a company called 3Shape rolled out a new scanner that can take 3,000 video images a second, and scan a full arch of teeth—14 teeth—in 30-40 seconds. That’s amazing.” Headquartered in Copenhagen, 3Shape touts its new TRIOS 3 as a handheld device that includes an intraoral scanner, and produces highly detailed digital scans as well as tooth-shade measurements (1).
When digital scans are combined with different modeling computer formats, such as OBJ and STL, the results are 3D images that are accurate at both the bone level and at the surface level, explains Lyndon Cooper, Stallings Distinguished Professor of Dentistry in the Department of Prosthodontics and director of the prosthodontics graduate program at the University of North Carolina. This gives dentists images of the teeth, the restorations, and the soft tissue (below).

When combined with different modeling computer formats, digital scans can produce accurate 3D images at the bone and surface levels. New capabilities are now adding the extra-oral environment, including the nose, lips, and other facial features, to produce “an entire digital patient,” days Lyndon Cooper, who is shown here working with a patient. Photo credit: Ramona Hutton-Howe, UNC School of Dentistry.
When combined with different modeling computer formats, digital scans can produce accurate 3D images at the bone and surface levels. New capabilities are now adding the extra-oral environment, including the nose, lips, and other facial features, to produce “an entire digital patient,” days Lyndon Cooper, who is shown here working with a patient. Photo credit: Ramona Hutton-Howe, UNC School of Dentistry.

“What is emerging right now, and what I think is very exciting, is this ability to make three-dimensional scans of the patient’s extra-oral environment—their lips, their eyes, their nose—and superimpose these to produce an entire digital patient,” Cooper says. “There is yet functional information that can be integrated into this to show things like the tracking of the jaw, so now we can begin to really assemble a virtual patient that has all the physical and functional attributes of the person who is sitting in the dental chair.”

CAD/CAM and the Virtual Patient

With this information, dentists can view 3D replicas of the patient’s teeth on the computer screen, and then apply CAD to suggest a design for a crown, bridge, or other restoration, which the user can modify as needed, Ferencz describes (below). “That design is then sent to another computer that looks like a computer numerical control (CNC) machine or a 3D printer, and that can transform plastic, wax, glass, ceramic, zirconia, metals into a very complex geometric shapes.”

New technology allows dentists to view 3D replicas of the patient’s teeth on the computer screen, and then apply computer-aided design that can ultimately help with the fabrication of a restoration, such as a crown or bridge. Here, Ferencz reviews a CAD design with laboratory technician Marissa Notturno. Photo by Pasquale Fanetti.
New technology allows dentists to view 3D replicas of the patient’s teeth on the computer screen, and then apply computer-aided design that can ultimately help with the fabrication of a restoration, such as a crown or bridge. Here, Ferencz reviews a CAD design with laboratory technician Marissa Notturno. Photo by Pasquale Fanetti.

A major benefit of digital design and computer-aided manufacture is that it provides very precise restorations. “If we were to compare 10 crowns made by hand to 10 crowns made by machine, I’d say that maybe one of the 10 handmade crowns would be better than those made by machine, perhaps three or four would be just as good, but at least half would not be as good,” Ferencz says. The reason is that hand-made restorations incur more variables that can reduce their success: Perhaps the technician is having a bad day, high humidity in the office is affecting one of the manufacturing steps, or the porcelain furnace isn’t calibrated correctly, he contends. CAD/CAM systems, on the other hand, eliminate those types of uncertainties, and consistently produce restorations that are fine-tuned for each particular patient.
The actual restoration isn’t the only application for CAD/CAM, according to Cooper. “Some of the most important things we make are surgical guides. For example, implant surgery has advanced to a point where we can plan it virtually, and then make a surgical guide with great precision to enhance the safety and the accuracy of treatment,” he says. A surgical guide rests in the mouth, often on adjacent teeth, and directs the surgery so that the implant is ideally (with remarkable accuracy and in three dimensions) anchored in the bone, and aligned with other teeth, while avoiding any unnecessary damage to nearby nerves. “This reduces the amount of time one spends doing the surgery, and increases the quality and safety of the surgery.”
In addition, new technologies are allowing dentists to enter the rapid-prototyping arena, creating accurate facsimiles of the final prosthesis, Cooper says. “We can make prototypes of teeth or implants that the patient can test for maybe an hour, a day, even weeks, and these prototypes can then guide the final design. The nice part is that with CAD, the design is completely iterative.” This allows the dentist to make sure the patient is happy with the comfort, esthetics, and the fit of the restoration before the final prosthesis is placed.
Same-day implants are also possible through similar milling processes used for rapid prototyping, and their success is improved with the use of surgical guides, Cooper says. He has conducted several studies of the so-called immediate loading of implants, in which a patient has a tooth (or teeth) removed, and a replacement made and installed all within a single visit (2, 3). His studies have shown that the removal of a tooth and its immediate replacement with an implant, an abutment, and a crown can have “very high aesthetic, phonetic, and health outcomes over a five-year period, when performed correctly by well-trained individuals. It’s not without risks, but it does offer the patient the opportunity to go without multiple surgical procedures and without a tooth, so I think immediate loading is here to stay, and guided surgery will help with the accuracy of the implant placement.”

Materials Behind the Technology

A basic requirement of making a good crown or other restoration – immediately loaded or not – is the availability of materials that are strong, have the right look, and are capable of being milled to specifications. As digital technology makes milling more accessible, whether the restoration manufacture occurs in a laboratory or right at the dentist’s office, new materials are necessary.

George Tysowsky is vice president of technology for Ivoclar Vivadent, which develops dental materials, including high-strength dental ceramics. Photo courtesy of Ivoclar Vivident.
George Tysowsky is vice president of technology for Ivoclar Vivadent, which develops dental materials, including high-strength dental ceramics. Photo courtesy of Ivoclar Vivident.

Over the last two decades, materials advances have introduced categories of high-strength dental ceramics. “Testing and clinical trials have shown that these ceramics rival the clinical performance of metal-supported restorations, such as porcelain fused to metal, which is a benchmark of dentistry,” says George Tysowsky (above), vice president of technology for Ivoclar Vivadent (4). Headquartered in Liechtenstein, Ivoclar Vivadent is a leading company developing a range of materials, products, and systems for dentists and dental technicians. He explains that the ceramics are a step up, because layered porcelain can chip off the metal. “With glass ceramics, the restoration is either cemented or bonded onto the tooth structure to provide a very natural-looking appearance, and yet provide excellent durability and support for patients, so they have a very reliable restoration.”
Strength is a requisite, particularly with new digital-based manufacturing equipment, he explains. “A dentist in the early ‘90s could mill out a restoration through digital technology and he could cement it, but the fracture rates were unpredictable, especially for molars and premolars, which are under heavy stresses (from chewing or grinding of the teeth). Now with the high-strength materials with higher density crystal structures, the resiliency and the durability are just leaps forward in improvement,” Tysowsky says.
The latest trend in dental materials today is high-strength zirconia (zirconium oxide). Although zirconia’s optical properties are not quite comparable to some other ceramic choices, he asserts, it does have a natural tooth-like appearance. Perhaps most importantly, zirconia can have up to triple the strength of other ceramics. “In clinical cases where you have people really clenching a lot or exerting great forces, zirconia is extremely resilient,” Tysowsky says (below). That strength also makes zirconia a good choice for restorations in very tight spaces. For instance, dentists sometimes have situations where they can’t reduce a tooth any more, so to prevent a root canal, they will design a thin restoration. Unless it is made of extremely strong material, such as zirconia, a restoration that thin will likely fail, he explains.
One of the materials that has drawn considerable attention recently is zirconia. Its high strength makes is an excellent candidate for dental work, says Tysowsky. He is sitting here in front of a scanning electron microscope, which is used in ceramic testing, Photo courtesy of Ivoclar Vivident.
One of the materials that has drawn considerable attention recently is zirconia. Its high strength makes is an excellent candidate for dental work, says Tysowsky. He is sitting here in front of a scanning electron microscope, which is used in ceramic testing, Photo courtesy of Ivoclar Vivident.

Like similar companies, Ivoclar Vivadent is continuing to improve materials to keep step with dental technologies. “Digital technology is evolving very rapidly, and it involves a combination of materials development, software development, and hardware development,” Tysowsky says. “We’re partnering with other companies so we can continue to optimize materials to be even more resilient and more optically pleasing for future-generation technologies.”

Digital Dentures and More

The melding of materials, software, and hardware expertise will be especially important for the trend toward developing new products, such as digital dentures, Tysowsky notes. “Making dentures has been a custom process and a manual process until now, so the ability to combine new technology and new materials means that dentures can now become thinner, stronger, more accurately fitting, and more comfortable for patients.”
Digital dentures will have other advantages, Cooper adds. “Milling dentures via digital dentistry is appealing from a biological process too, because the new materials, including industrially processed acrylics, have some favorable properties in terms of their biocompatibility: They aren’t as porous, they may not collect bacteria as rapidly, they are highly polished, they are accurate, and they may have less distortion with temperature and daily use.”
Additional dental products and technologies may soon make their appearance. Ferencz notes that the demand is high for an intraoral scanner or camera that can deliver images through the gum tissue, as well as through saliva and blood. “Right now, the prepared tooth has to be absolutely visible to the camera or scanner, and that’s a challenge because when the dentist is working under the gum, there’s bleeding and there are sulcular fluids.” Such a product is still only on the wish list, he remarks, “We’re all definitely waiting and hoping for it.”
Real-time surgical navigation, on the other hand, is already in the works, says Cooper. This type of system shows the surgeon exactly where an implant is going while he or she is placing it. “That seems almost like a futuristic view, but I think we’ll see it in use probably within the decade,” he adds.
Another key advantage of digital dentistry is that it enables better communication between dentists and the technicians, Cooper believes. At present, the technician often has more direct access to technology and its capabilities, so as the interface between the dentist and the technician improves, both will enjoy a better visualization of what is possible. At the same time, digital dentistry will allow patients to be more engaged in their oral care, he says. They can also envision the plan in an engaging 3D visual manner that can inspire and clarify proposed therapies. “We must see an effort to create systems where patients have access and ownership to all of this data, so when they leave the dentist’s office, they’ll take their digital file with them. That will be important.”
In addition, the informational aspect of the digital technology will provide an unprecedented continuity in care, particularly in terms of tracking the progress of a patient throughout his or her life, including changes in gum recession or the patient’s bite. Cooper remarks, “Without a doubt, I think there will be a growing appreciation for the archival nature of digital technology.”
Another major shift in digital dentistry will come with additive manufacturing, according to Ferencz. Unlike milling, which is a subtractive process because it removes material to sculpt a crown or other restoration, additive manufacturing builds up the restoration through a process such as 3D printing. “One of the big breakthroughs for us will come when we can additively manufacture a ceramic material, because not only will the fits will improve dramatically, so will the ease of use.”
Tysowsky agrees. “The additive technology will be the future with 3D printing and other technologies that will allow you to take slurries of ceramics, and build up a crown, or create fillings or other restorations. That’s the next evolution, but it’s still a work in progress.” At this point, no one has been able to demonstrate the feasibility of additive manufacture of dental ceramics, he notes. “I’d say it’s perhaps several years out, but that’s just a guess because everybody’s R&D is still in proof of concept.”
For now, patients will still see the familiar tray of poking tools and the suction device, but they will also continue to see their dentists’ offices metamorphose. As they do, both they and their dentists can look forward to quicker visits, and safer, more comfortable, and better-looking results.

References

  1. “TRIOS reinvents impression taking,” 3Shape website.
  2. L. F. Cooper, F. Raes, G. J. Reside, J. S. Garriga, L. G. Tarrida, J. Wiltfang, M. Kern, and H. de Bruyn, “Comparison of radiographic and clinical outcomes following immediate provisionalization of single-tooth dental implants placed in healed alveolar ridges and extraction sockets.” Int. J. Oral Maxillofac. Implants, vol. 25, no. 6, pp. 1222–1232, 2010.
  3. L. F. Cooper, I. J. De Kok, F. Rojas-Vizcaya, P. Pungpapong, and S. H. Chang, “The immediate loading of dental implants,” Compend. Contin. Educ. Dent., vol. 28, no. 4, pp. 216-25; 2007.
  4. Ivoclar Vivadent.

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