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Inside Dentistry

August 2013, Volume 9, Issue 8
Published by AEGIS Communications


Small Digital Dental Labs

Local labs assist when cases are complex or time-sensitive

Bob Cohen, CDT

Until recently, dental laboratory analog workflows have remained stagnant for decades. With the accelerating introduction of new digital technologies and materials—particularly computer-aided design (CAD) and computer-aided manufacture (CAM) applications—the landscape of products and relationships between dentists and commercial laboratories has transitioned to provide superior products and reduced manufacturing cycles.

These digitally manufactured products are stronger, faster, and more economical. In addition, fabrication of the most complex cases can now be automated. This automation has significant advantages for laboratories, dentists, and patients. The following will touch upon CAD/CAM for the most complex cases and provide a laboratory crown-in-an-hour workflow.

Izir Bridge Protocol

When evaluating automation of complex cases, there are many advantages to digital production. For instance, the Prettau® (Zirkonzahn, www.zirkonzahn.com) bridge and the Izir™ (Advanced Dental Technologies, www.adt-us.com) bridge (Figure 1) are implant-supported, screw-retained restorations that are digitally fabricated and made using zirconia, the strongest all-ceramic material available. These restorations can be fabricated for any number of implants. As a result, they are a viable treatment option for cases ranging from single units to 14-unit bridges.

The final restorations are fabricated using CAD/CAM technology. This includes the digital design as well as the milling of the restoration from a zirconia disk. Once milled, the green-state zirconia is multi-shaded for improved esthetics. Next, the bridge is sintered at a high temperature for 8 to 13 hours. Once sintered, pink porcelain is added to the Izir zirconia bridge to create the illusion of soft tissue. This minimal porcelain application represents the vast majority of analog work needed to fabricate an Izir restoration.

The Izir protocol includes fabrication of a CAD verification bridge (CVB) (Figure 2) that is used to confirm all essential elements of the digital design. Once treatment is planned and designed, the Izir CVB is milled from a polymethyl methacrylate with subsequent intraoral try-in. Design elements to be evaluated include—but are not limited to—fit, tooth placement, tooth form and size, hygiene, function, incisal edge placement, and occlusion.

The CVB may also be used as a screw-retained provisional. When using the Izir protocol and CAD/CAM, the digital design file of the CVB will be saved long term. This has several advantages. First, once the CVB is confirmed appropriate for all design criteria, the original CVB digital design file is brought back into CAM software and an identical bridge is milled for the final zirconia material. If the CVB design requires small alterations, the original CAD file is loaded back into the design software and all needed changes are made prior to fabrication. Fabrication, confirmation of the CVB, and subsequent manufacturing of the final restoration use the original CVB design file for fabrication. This digital workflow ensures that the final restoration will be an exact duplication of the CVB. This provides a very predictable end result while keeping the treatment protocol practical.

In addition, if for any reason an Izir case needs to be remade, whether several months or several years later, the laboratory simply finds the original file and mills a new case. As a result, the cost of remaking an Izir bridge is a fraction of the cost of making a new one. Longer term restoration failures can therefore be remade with minimal appointments, or possibly even a single appointment. When needed, the clinician can contact the lab that fabricated the original case and request a duplicate case of the original design file. The lab simply pulls the original .stl file and remills the needed new case. If the reason for remake is breakage, the lab can edit the design file and add material to the fatigued area. In this unforeseen event, it is possible to schedule the patient for one appointment to unscrew the old case and screw in the new Izir restoration.

Because implants have been popular for several decades, many patients are now returning for replacement of old, worn out prosthetics. With the advent of digital manufacturing, this process is now much more streamlined and cost effective. No new impressions, bite registrations, or try-ins are needed. Single appointment complex case prosthetic replacement is now viable and available. Complex case treatment through digital manufacturing is more predictable, enables use of state-of-the-art materials, and reduces cost significantly.

Offering of Izir will provide dentists and dental labs a meaningful differentiation for their practices. It can easily be accomplished while providing services to the most needy patients and still maintaining high profit margins. The rapid advancement of CAD/CAM for dental labs has now made it far more economical to enter the CAD/CAM market and also provides improved ease of use when compared with just 5 years ago. In the unlikely event that a replacement bridge is needed, the process for manufacturing a new restoration is a small fraction of the original restoration. Prescribing complex treatment using analog workflows is simply more expensive and offers no backup plan when problems occur.

Crown-in-an-Hour

In addition to working with laboratories to provide complex digital prosthetics, there is now the potential for new workflows that can improve patient experience and reduce costs in the dental practice. The 1-day crown, or “crown-in-an-hour,” protocol no longer requires chairside milling systems. Through recent advancements in CAD/CAM, small local laboratories can now invest in solutions that do not require huge investment or large volumes of work generate a favorable return on investment. In addition, intraoral scanners such as the new 3Shape’s Trios® (www.3shapedental.com) now provide instant data to the dental lab. With the combination of comparatively small investments, small local laboratories can now afford CAD/CAM that can quickly produce lithium disilicate (Figure 3) or resin nanoceramic materials such as Lava™ Ultimate (3M ESPE, www.3mespe.com). Lithium disilicate can be used for inlays, onlays, crowns and some 3-unit bridges.

Over the past several years, there has been pressure on small local labs. Many have gone out of business. Five years ago, there were approximately 13,500 labs in the United States. Today that number is under 10,000. The closings have occurred for a number of reasons, including outsourcing to foreign countries, in-office milling, large labs moving rapidly to CAD/CAM, and a general slowdown in the economy. It will now be possible for small local labs to obtain a significant advantage by working with dentists within a 20 to 30 mile radius of the dental lab, as the crown-in-an-hour workflow cannot be provided by offshore labs or large national players.

For dental practices, the benefits of digital impressions and a crown-in-an-hour with a local lab are many. Until the advent of the 3Shape Trios, dentists were required to spend more than $100,000 to provide this service. Maintaining an inventory of milling blocks and tools, keeping up with machine maintenance, and the steep learning curve of CAD and finishing techniques also required a significant investment of time and money.

With the current availability of sophisticated laboratory CAD/CAM, smaller local labs can now partner with dentists who use an intraoral scanner that provides instant data (some devices do not make data available immediately) to provide the crown-in-an-hour workflow. For the dentist, the investment is a small fraction of the cost to purchase the entire CAD/CAM system and related items. The benefit for the laboratory is significant market advantage in the geographic region surrounding their business.

Final Thought

In terms of dental-specific CAD/CAM and related dental applications, we are moving today from a period of infancy to more mature digital solutions. The advantages of moving analog workflows to digital have been well documented, and future advancements will likely go even further beyond current benefits.

About the Author

Bob Cohen, CDT
Founder, Advanced Dental Technologies
Stoneham, Massachusetts


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Image Gallery

Figure 1 The Izir bridge for complex cases can be fabricated with lab assistance.

Figure 1

Figure 2 A fabricated computer-aided design (CAD) verification bridge, part of the Izir protocol.

Figure 2

Figure 3 Lithium disilicate final restoration created using CAD/CAM technology through a small, local lab.

Figure 3