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The Smile Goes DigitalThe Smile Goes Digital

As a result of new rapid prototyping and manufacturing processes, the $8.8 billion U.S. dental restoration industry is transforming from a craft into a digital business.1 Just a few years ago, when patients needed any kind of replacement teeth, a dental technician designed what the dentist ordered using a centuries-old process of sculpting the restoration in wax that was laboriously heated over an open flame.

Bob Steingart

January 1, 2010

16 Min Read
The Smile Goes Digital

As a result of new rapid prototyping and manufacturing processes, the $8.8 billion U.S. dental restoration industry is transforming from a craft into a digital business.1 Just a few years ago, when patients needed any kind of replacement teeth, a dental technician designed what the dentist ordered using a centuries-old process of sculpting the restoration in wax that was laboriously heated over an open flame. Whether the dental restoration was a single crown, a complete set of dentures, a bridge with several adjoining teeth permanently placed in the mouth, or a removable appliance onto which a few denture teeth are affixed (called a partial), the restoration was produced entirely by hand.

This partial framework was designed using a touch-enabled dental CAD/CAM system. Digital technologies are transforming the speed in which dental labs can create restorations such as crowns, bridges, partials, and veneers. Images courtesy of MINOT DENTAL LABORATORY.

Today, dental labs are adopting CAD/CAM systems and rapid prototyping and manufacturing techniques at a vigorous pace. The number of dental restorations fabricated using CAD/CAM technology is expected to grow 75% by 2013.2 Working digitally and using new techniques and materials offers benefits to patients, labs, and dentists.

CAD/CAM has also revolutionized other industries, such as medical modeling, that previously depended on highly skilled individuals to create models by hand. Patient-specific implants such as hips and shoulders, as well as replacement parts for cranial bone pieces that are missing due to trauma or disease, are now digitally designed much faster than by hand and fit precisely. Custom orthotics and prosthetics such as noses and ears are additional examples. As the CAD/CAM evolution in dentistry continues, the opportunity for other industries to benefit is growing. New design ideas involving surgical planning and drilling guides, materials, and techniques that are initially applied in the dental industry may spur innovations in medical modeling and vice versa.

Although there will always be artistry in creating dental restorations, digital processes and new production methods enable them to be created efficiently, with better aesthetics and a precise fit. A crown that may have taken two to three weeks for the lab to create just a few years ago can now be produced in a dentist’s office within an hour. Similarly, aesthetic restorations like veneers are becoming more accessible and affordable due to advances in digital design and manufacturing processes. OEMs can take advantage of this trend by speaking with technicians about their needs.

This image shows a three-unit bridge that was created using a dental CAD/CAM system.

New Digital Processes

Digital processes that address industry challenges and add efficiencies are arriving on the market at a pivotal time in the dental industry. Demand for aesthetically pleasing restorations is on the upswing as baby boomers age, dentists aim to preserve more of the existing tooth structure, and patients are seeking more cosmetic dentistry. New digital methods are made possible by several systems and processes.

Dental CAD/CAM Systems. The introduction of zirconia in the 1990’s for use in milling copings—the thimble-shaped substructure that covers the tooth and forms the foundation of a crown—began the transition to digital design. In recent years, dental manufacturing processes such as 3-D printing, aesthetic materials for milling, and the increase in dental implants have accelerated the demand for CAD/CAM systems tailored to meet the design challenges of patient-specific dental restorations.

In dental labs, the benefits of using CAD/CAM systems extend beyond time and cost savings. Dental CAD/CAM systems’ digital files can drive many output devices, whether it’s a milling machine for carving an anatomical restoration in translucent porcelain, printing a 3-D coping in resin for subsequent casting, or printing the restoration in precious metal. Additionally, digital systems reduce waste because they enable labs to do away with Bunsen burners and reduce their use of plaster and other materials. In the case of new fabrication techniques, digital systems can reduce the energy consumption associated with casting ovens. The accuracy of digitally modeled restorations also allow dentists to quickly affix, or seat, restorations into a patient’s mouth.

New dental CAD/CAM systems use components that have been tightly integrated to take advantage of the latest technologies while providing accurate and consistent results. For example, such a system could include a 3-D scanner, design system, and resin printer, and case management software.

A lab designed this full-contour crown, which is fabricated as an all-ceramic pressed restoration.

In the new digital work flow, lab technicians start with a digital scan of the impression, or a digital file produced by an intraoral scanner at the dentist’s office, which can be electronically sent to the lab. Using the computer, technicians design, refine, and iterate on the restoration where exacting thicknesses, settings of mesh patterns, margin lines, and locations of clasps can be specified. Once the digital designs are complete, the system automatically creates 3-D model files for fabrication.

3-D Printing. With a CAD front end, labs can explore a range of rapid manufacturing technologies, including 3-D printing. Used for many years in numerous industries to create product prototypes, the presence of 3-D printers in the dental industry is relatively new.

3-D Printing Applications

The adoption of 3-D printing has been accelerated by innovative materials and printers that have evolved to a new level of speed and sophistication. These printers are being used to create a variety of dental applications.

Working and Study Models. Using digital design files, 3-D printers can readily make working models (the master model or a duplicate of the master model used to design and fit the dental restoration) and study models (a diagnostic model used for planning dental procedures), instead of requiring a lab technician to create them by hand.

These veneers were designed using a customized, touch-enabled 3-D veneer modeling application. Image courtesy of REMEDENT INC.

Making an accurate-fitting dental restoration heavily depends on the accuracy of the original patient impression, which is used to create the master design model. One of the main benefits of digitally creating these types of models is the speed with which the accuracy of the impression can be assessed. If necessary, a new impression can be made before the patient leaves the chair and before the lab spends any time designing and producing the restoration. An intraoral scan of the patient's teeth made in the dentist's office can be sent to a lab in digital form, and from there, a positive model can be printed in a plasterlike material.

With the manual method, if a distorted impression is taken, problems don't typically emerge until the master model is made and analyzed by an experienced lab technician. Manually creating a master model can take about 45–75 minutes (this includes spraying for contaminants, mixing, pouring, drying, and trimming time). In contrast, digital impressions are very accurate, and if there is a problem, most scanners show holes or other issues on the screen immediately. This allows the dentist or support staff to immediately rectify any issues. The digital file is then printed to produce the working model, and the technician can begin the design phase.

Additionally, study models can be efficiently printed out at the same time as the master model, using the same patient scan.

Orthodontic Applications. For example, in the case of invisible aligners, a digital system can scan the patient’s current arch and reposition the teeth into the desired result. The CAD system creates a series of 20 digital models depicting the intermediate steps required to achieve the final result. Each model is then printed out in a plasterlike material, enabling a design with a precise fit of the aligners at every stage.

Cast or Pressed Resin Patterns. New dental CAD/CAM systems give labs the flexibility to digitally design removables (partial dentures) as well as fixed restorations (crowns and bridges) that are printed in resin and fabricated using traditional methods and materials, including popular alloys, flexible nylon, porcelain composite, and glass ceramic. Veneers are also being digitally designed, printed in resin, and produced in porcelain.

Modeling software generates views of veneers at several different angles and displays their precise shape and thickness. Image courtesy of REMEDENT INC.

Drilling Guides. The increase in dental implants has created the need for a viable way to manufacture a patient-specific drilling guide that assists dentists in placing abutments (a titanium cylindrical connector placed on top of the implant that provides the foundation for a crown), based on the patient’s computed-tomography data and the actual implant design. The drilling guides can be printed in a biocompatible resin or milled in a number of materials.

Restorations. Restorations that are direct-printed in metal require little finishing work. New processes using precious metal powders, such as gold or titanium, can be printed and then sintered to rapidly manufacture metal restorations such as copings, full metal crowns, or partial frameworks. Given the advances in additive fabrication with biocompatible materials, 3-D printers can also streamline the creation of try-ins (a completed partial framework with denture teeth that have been placed in wax). Dentists use try-ins to test fit and occlusion.

Milling. Although dental milling has been around for about
15 years, there have been advances in materials, speed, and cost. In addition to being able to digitally design restorations, ceramic and glass materials can be milled to create natural-looking substructures for crowns and bridges. As a result, labs and dentists can rapidly deliver strong, visually appealing restorations to their patients that are less labor intensive and time consuming to produce. Output devices, whether mills or printers, are faster than previous machines and are being produced in a range of sizes that make them more affordable for dental labs. There are also future promising technologies that could enable labs to “print” teeth or complete sets of dentures.

Benefits Outweigh Challenges

New CAD/CAM systems and digital processes present some important choices and challenges for dental labs. It could improve productivity so dramatically in one area of the business that lab owners might need to rethink how to most effectively deploy their resources. For example, a lab that has several technicians designing and waxing partials by hand could free up some of the staff by designing digitally.

Choosing what level of design control labs want to maintain is a critical concern. Labs can choose to scan, design, and fabricate in-house, or scan and design in-house and outsource production. Many labs find that having the design capability in-house provides enough control, while others prefer also having control over the fabrication process. Making this choice can depend on a variety of factors, including a lab's growth strategy and its interest in gaining new revenue streams by offering design and fabrication services to other labs.

Carefully evaluating not only which CAD/CAM program is right for their business but also how they want to be serviced is another key challenge that lab owners face when adopting digital technology. Some advanced CAD/CAM systems can be used to design multiple types of restorations. Some labs might choose systems that offer tightly integrated hardware and software and responsive, one-stop service, rather than disparate components offered by multiple manufacturers. These types of systems help maximize up-time for labs, increase productivity, and provide consistent quality.

Another hurdle that labs may face is a lack of staff experience with highly technical equipment. Although some technicians send text messages, surf the Internet, and communicate via e-mail with ease, other technicians may not be as computer literate. They may jeopardize their lab’s future by lagging too far behind in embracing new technologies that can help expand and streamline their businesses. CAD/CAM systems that make working digitally natural and intuitive—emulating the traditional tools and techniques that experienced technicians may prefer—can help ease the transition to digital systems.

Digital design, when combined with new fabrication techniques, offers labs more choices and a streamlined design and production process. It also enables labs to produce suitable fitting and often less-costly restorations. The following are two examples of how digital technology is benefiting patients and dental practitioners.

Veneers Go Digital

Remedent Inc., a Belgian cosmetic dentistry company, combines CAD/CAM, rapid prototyping, and rapid manufacturing techniques to design and produce very thin and precise-fitting veneers. After extensive R&D, the company launched the GlamSmile veneer concept in 2007 and has since further enhanced the product by incorporating a number of digital technologies. In the past, veneers were handmade in the dental lab. Technicians hand-waxed models to fit each tooth even though it was difficult, if not impossible, to achieve the desired thinness in wax. In addition, a good wax-up took a dental technician at least one hour per veneer. Designs for specified veneers were then finalized, fabricated, and provided to the dentist as individual porcelain veneers for one-at-a-time placement on the patient’s teeth using adhesive techniques.

With these particular veneers, the company transitioned to using an all-digital system including digital scanning, CAD/CAM design, and a proprietary fabrication technique. Based on the patient’s impressions, a model was scanned in a 3-D scanner. The information was imported into a tailored 3-D veneer modeling application that was developed using a customized version of design software. Since technicians design by holding a haptic (touch-enabled) device instead of a computer mouse, they could produce thin veneers that precisely fit a patient’s existing tooth structure in 10 minutes per veneer instead of an hour. The veneers are on average only 0.5 mm thick, but the technician can vary the thickness to create an aligned dental arch. Because the source file is digital, the traditional “lost wax” fabrication process is made precise and efficient by the 3-D printing of resin patterns of the ultrathin veneers, which are used to produce the final porcelain version.

The veneer design system also allowed the company to offer a digital preview system to dentists. The software can readily compile veneers into views at various different angles. The preview files show the exact shape and thickness of the future veneers and can be sent to the dentist for evaluation and approval.

Beyond its use of digital technology to accelerate the design of veneers, the technology also incorporates a patent-pending tray delivery system that precisely positions the veneers and allows the dentist to apply them all at once, instead of individually.

Although CAD/CAM offers benefits to designing veneers, there were challenges too. This company used proprietary materials and processes to manufacture their veneers; therefore, the design and fabrication processes needed to be fine-tuned, which resulted in making specific adjustments to ensure consistent results. For example, the software optimizes the design to the 3-D printer's resolution, providing the fine edges required in the GlamSmile veneers.

Ceramic Crowns and Bridges

Pressing ceramic, referred to as pressables, is a manufacturing technique that allows for a fast, cost-effective, and natural-looking outer layer to be applied to crown and bridge work. For years, dental labs have maintained pressed ceramics equipment on-site for cases in which aesthetics dictated its use, such as for anterior teeth. However, labs have avoided their widespread use after the publication of studies revealing that the materials were not as strong as other restoration types. However, within the past five to seven years, new ceramic composite materials have provided enough strength to make them superior for posterior teeth, where chewing and grinding create intense pressure.

Some CAD/CAM systems support the design of full-contour crowns (overstructures), bridges (multiple replacement crowns affixed together), and copings (substructures). Driven by the precision and speed of these advanced systems, pressed ceramic processes can enable labs to deliver a finished crown in 15–30 minutes. This shorter time frame is compared with the 90 minutes or more required for the traditional method of hand-stacking layers of ceramic onto the base substructure of a crown. As a result, the pressables business has recently seen a resurgence.

In the traditional porcelain-fused-to-metal (PFM), also known as the hand-stacked porcelain method of fabrication, after a metal or zirconia substructure (coping) is made, the ceramist spends one to two hours applying three or more layers of porcelain. This process ensures that the metal or zirconia coping resembles a natural tooth. Each layer also requires heating and cooling time, as well as hand grinding before the next layer is applied. The ceramist performs intensive manual checking of each crown to ensure proper contour and color match, and then adds stains and glaze for the final shade matching.

With pressables, dental labs can make two-part crowns that include metal or zirconia copings, or they can make all ceramic restorations (that require no copings), which are directly bonded to the prepped tooth. In either case, once the mold is ready, an ingot of ceramic is heated and pressed into the mold to create a pearly, luminous restoration that is custom shaped to the patient’s dental morphology.

For example, Minot Dental Lab (Minot, ND) moved to an all-
digital process for creating fixed restorations such as crowns, bridges, and partials. Sixty percent of the lab’s crown and bridge work uses pressable technologies, with the balance done as PFM. Pressing all-ceramic restorations or pressing ceramic over zirconia can produce a superior fit, as well as aesthetic appearance over PFM approaches. Pressables can also be easier and less time consuming to manufacture than typical PFM processes and are often indicated by the condition of the tooth, because they are strong.

One of the lab’s cases involved a patient who completely sheared off the top of a molar and required a crown to restore the tooth. The lab chose an all-ceramic pressed restoration for its appearance and high tensile strength, which could withstand the constant pressure of the chewing required by a molar.

The dentist prepared the top of the patient’s remaining tooth. Using one of its new dental CAD/CAM systems, the technician designed a full contour crown that anatomically matched the patient’s other teeth in two minutes. The digital design was then printed in resin, which was used to create a mold. In one final step, the ceramic ingot was pressed into the mold to produce the final restoration.

Conclusion

Digital technologies are revolutionizing the dental industry at a time when the demand for quality is matched by the need for speed. The same scanning, CAD, rapid prototyping, and rapid manufacturing processes that have transformed traditional manufacturing industries, such as automotive and aircraft, are now helping to create the next crown or veneer. From using powdered gold to print foundations for crowns on a 3-D printer to creating a designer smile with the veneers placed on a patient’s teeth in an hour, it is an exciting time for the dental lab industry, and the benefits extend directly to the patient.

 

References

1. iData Research, “U.S. Market for Dental Prosthetics and CAD/CAM 2008,” Rapid Today, June 2008; available from Internet: www.rapidtoday.com/dental.html.

2. P Johnson, “CAD/CAM Smart-Sourcing,” Dental Lab Products, October 2008; available from Internet: http://dentalproductsreport.com/articles/show/dlp1008_ft_cc-smart.

Bob Steingart is president of SensAble Dental Products, a group within SensAble Technologies Inc. (Woburn, MA).

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