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Digital Impression Technology
The current status of new advances and what to look for in the future.
Since the introduction of the first intraoral digital impression system intended strictly for indirect restorations in 2006, clinical adoption of the technology has been relatively slow. In the beginning, a very small number of early adopters dove in quickly, but the vast majority of the industry has been resistant. The impact of the economic downturn in 2007 left many clinicians with fewer restorative opportunities, which has led to decreased production and in turn, tighter budgets. The cost factors associated with those initial systems were relatively high.
The initial technologies launched onto the market involved two types of capture technologies. One captured a series of still images stitched together for the final three-dimensional (3D) “impression.” The second used continuous video capture to develop the final 3D image. A light application of titanium-dioxide powder applied to the tooth surfaces is required for some, but not all, digital impression systems.
CEREC® technology from Sirona Dental (www.sirona.com) is recognized as the pioneer of the “direct/indirect” digital impression capture category, introducing its technology almost 30 years ago. Initially the system was designed as an in-office capture and mill option. The 2nd generation Bluecam evolved as a highly effective capture option with excellent clinical results and provided a 3D stereolithography printed resin model option for the execution of multiple-unit complex-treatment protocols. The CEREC® AC Connect software (Sirona Dental) for web-based communication made the off-site production of single units in the laboratory a realistic option. The CEREC® Omnicam (Sirona Dental) is its most recent introduction. The technology is vastly improved with the elimination of powder requirements and the addition of 3D video capture in natural color. For clinicians, the color feature enhances patient communication and case acceptance.
The E4D system from D4D Technologies (www.e4d.com) is the other major participant in this category of digital capture and in-office restoration production. The iTero™ system from Align Technology (www.aligntech.com) has the longest track record in the capture-only category. It operates with a laser and still camera capture through parallel confocal imaging. Multiple images are captured and stitched together at completion. The auto-focus feature eliminates the depth-of-field issue, allowing the operator to rest the camera on the unpowdered teeth. It offers a reduction critique at the completion of the scan informing the clinician of the need for additional reduction for the intended restoration.
The iTero™ unit has been exceptionally accurate, reducing prosthetic remakes to less than 0.5%.1 This system also introduced the concept of concurrent manufacturing. This concept allows the digital STL file to be sent directly to a fabrication system (milling, 3D stereolithography wax printer, or alloy laser sinterer) for production of the restoration at the same time the milled models are being produced. At the completion of each component, they are combined, confirming adaptation, and completed. This has become a more common aspect of systems available today. Recently acquired by Align Technologies, the system will be very active in the Invisalign digital orthodontic marketplace.
3Shape’s TRIOS® digital impression technology (www.3Shape.com) is the newest addition to its product line. It operates with confocal microscopy, capturing thousands of images seamlessly. It offers a reduction critique at the completion of the scan, informing the clinician of the need for additional reduction for the intended restoration. 3Shape represents the best-in-class in the laboratory-scanning sector. Their open approach makes the scanners compatible with any production technology. The combination of software from the TRIOS and the laboratory systems makes it possible to virtually develop any fixed restoration—including digitally articulated diagnostics, temporization, and final restorations—without the need for a conventional impression.
Recent advancements in the design-and-capture technology of a next generation of “capture-only” digital impression systems promises to provide faster, more accurate data at lower costs. The new 3M ESPE 3M™ True Definition Scanner 3D video-capture technology (www.3m.com) is an update of 3M’s original Lava™ C.O.S. (Chairside Oral Scanner) product with a small wand that mimics the look and feel of a handpiece. However, an application of titanium dioxide powder is still required. The STL file is stored in the 3M™ Connection Center, which is supported by an open and secure cloud-based platform. This open approach allows many types of fabrication technologies to download the file and produce models, concurrent restorations, or modeless restorations. The company recently announced a specific “connectorship” with D4D Milling Technology. It is also entering the marketplace at a lower cost than any preceding system of its type.
Glidewell Laboratories’ IOS FastScan® intraoral impression technology (www.glidewell.com) scans 40-mm per second, with the scan technology moving automatically within the wand housing. An application of titanium dioxide powder is required. Ego-motion technology is used to optimize image stabilization. Built-in motion detection software virtually eliminates hand-movement distortion, capturing exceptional surface resolution and detail on every scan. With the IOS FastScan Digital Laboratory System, the system can be used in the laboratory to scan impressions or models. Both arches and centric relation can be quickly scanned in less than 4 minutes. It is an optimal acquisition system to generate digital models for export directly to the design software for crown and bridge, custom implant abutment, and full orthodontic cases. Scanned cases can be submitted electronically to the company’s central manufacturing facility to order copings or full-contour restorations. Other lesser-known capture-only technologies on the market include the MHT (www.mht.com) and densys 3D systems (www.densys3d.com).
Although cost reduction and various options should bolster the sales of digital impression systems, the interest in capture-only systems may continue to lag behind technologies that offer the complete opportunity for chairside data capture and restoration development. This conjecture is based solely on the belief that the evolving generations of clinicians prefer the time savings and improved service to the patient as well as an apparent improvement in patient acceptance of needed treatment. Recent dental school graduates are also much more accustomed to a digital lifestyle and therefore are more adaptable to the changes as the new norm. The capture-only option should evolve as minimal mainstream technology, replacing traditional impressions because of its many benefits, including patient comfort, accuracy, and ultimately cost savings in all aspects.
The Crystal Ball
Inevitably, technologic development will provide an apparatus that is able to record hard- and soft-tissue data regardless of direct visibility. This will eliminate the current limitation of a required sight line of the margin in the sulcus.
The new Seikowave e-Vox Micro scanner (www.seikowave.com) is perhaps an example of such a method. The e-Vox Micro is a high-speed, handheld 3D microscope suitable for a wide variety of inspection applications. The unique optical system enables the e-Vox Micro to accurately measure semi-transparent objects. This enables measurement of live teeth without the need for sprays or powders. The technology is just entering the dental marketplace and information is therefore limited.
S-Ray Incorporated (www.s-rayinc.com) has been issued a US patent for its unique way of using ultrasound for numerous dental applications. While ultrasound has been a proven technology in virtually all aspects of medical diagnostics since the 1940s, the S-Ray is the first venture that claims to have solved the puzzle to enable ultrasound to be used in dentistry. The S-Ray product is a medical device and requires approval by the Food and Drug Administration before it can be offered for sale. The company is developing a product that will ship, on a limited release basis, to dental professionals in July of 2013. If the FDA approves the scanner for sale, it will be sold at that time. If not approved for sale, the company is planning on using the limited-release products on an “investigational” basis with appropriate regulatory approval.
These are just two examples of what is being investigated. The possibilities are endless and developing almost daily. The only certainty is the inevitable changes on the horizon.
No discussion of digital impression systems is complete without including model fabrication technology. The next big change for the laboratory community will occur with the ability to productively and cost effectively develop working casts on-site. Current technology offers milling and 3D stereolithography as methods of cast production. The author believes that rapid prototyped printing of resin casts will evolve as standard protocol due to cost and time efficiency. This will eliminate the well-documented potential transfer for errors, leading to more predictable delivery and satisfied customers.
Of course, the real paradigm shift looming on the horizon is “modeless” technology. This capability currently exists for the fabrication of single-unit restorations. Accompanied by digital images for color communication, this can work very well. The ability to generate accurate multiple units in the same quadrant or opposing each other at a predictable level is coming. It is simply the older generation in the industry that is most comfortable having the model for visible pre-clinical confirmation. Of course, this is the technology that for all intents and purposes, eliminates the need for the majority of off-site laboratory processes. Only large, complex, fixed and removable prosthetic treatments will require off-site management.
The next frontier for dental technicians is a return to the in-office work environment. The skill sets required will be the understanding of dental anatomy and esthetics, as well as the digital skills to manage software and hardware for diagnosis, indirect fabrication, and custom characterization of milled or printed fixed restorations and the ability to adapts to new materials and technology.
1. iTero™ [brochure]. San Jose, CA: Cadent Inc., a subsidiary of Align Technology, Inc.; 2011.
About the Author
David Avery, CDT, AAS, is the director of professional services at Drake Dental Laboratory.