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Inside Dentistry

February 2011, Volume 7, Issue 2
Published by AEGIS Communications


Digital Dental Impression Systems

There have been a number of recent advancements and integration into everyday dental practice.

By Nathan S. Birnbaum, DDS, CAGS(Prosth) | Heidi B. Aaronson, DMD

Many advancements in the art and science of dentistry have come about as evolutionary changes, as in the progression of tooth-colored restorations from the earlier silicates of the 1960s to the nanohybrid composites of today, or porcelain jacket crowns to the pressable ceramics and the zirconia and lithium-disilicate ceramic restorations of today.

In technological parlance, a “mashup” is a blending of two apparently unrelated things into a new creation. In the case of digital impressioning, the creators of the impression-taking devices have introduced scientific developments in the fields of optics, digitization, and CAD/CAM into the art of capturing impressions of prepared teeth and surrounding structures to develop 3D digital and even physical representations from which dental restorations can be made.

Unlike many other improvements in dental technology that have taken place, particularly within the past decade, which employ evolutionary changes in materials and instruments, the rapid explosion in the field of digital impressioning has been nothing short of revolutionary.

Disruptive Technology that is Here to Stay

The development and growing use of soft-tissue lasers as an improvement over hyfrecators and electrosurgical scalpels and the introduction and wide acceptance of digital radiography as a safer and more versatile advancement over conventional film radiography are both evolutionary improvements using new technology. They achieve better-quality results using the same paradigms of tissue curettage and cauterization and radiographic imaging with X-radiation, but with newer technological tools.

Digital impression taking, on the other hand, is revolutionary, in that it creates a paradigm shift away from the concept of taking a physical impression in the patient’s mouth with distortable, often foul-tasting elastic materials and instead uses technology to change all but the concept of developing an accurate replica of the teeth being impressioned.

In early 2009 the authors wrote in Inside Dentistry1 about the remarkable technologies that have brought digital impressioning devices into the dentist’s operatory. In the brief time since then, the manufacturers of these systems have advanced the integration of their hardware and software with dental laboratories, have broadly expanded the scope of indications for the use of their respective systems in the dental office, and have enhanced the educational and training programs for the dentist and dental team members.

The leading systems the authors presented last year are still the front-runners in the field of digital impression-taking devices. They include the CAD/CAM products CEREC® (Sirona Dental Systems, www.sirona.com) and E4D Dentist (D4D Technologies, www.d4dtech.com) and the dedicated impressioning products Cadent iTero™ (Cadent, www.cadent.com) and Lava™ Chairside Oral Scanner C.O.S. (3M ESPE, www.3mespe.com).

Several promising new digital impressioning apparatuses have entered the market in the past few years, including FastScan™ (IOS Technologies, www.ios3d.com), Densys3D Solution (Densys, www.densys3d.com), and (directScan™, Hint-EL/Fraunhofer, www.hintel.de).

Integrating the Dental Practice and the Laboratory

Clon 3D (www.clon3d.com) is launching a new business model in which the dentist rents from the dental laboratory a digital scanner that connects to a PC via a USB 2.0 cable. The Progress IODIS™ (Intra Oral Digital Impression System) is capable of capturing a digital impression that can be uploaded to the laboratory in standard .STL format. Employing an open-architecture system, the scans are compatible with most CAD platforms. The dentist can thereby become involved with digital impression-taking without significant capital expenditure.

For the past several years, dental laboratories have been eagerly adopting digital impression systems that enable them to scan models and/or conventional elastomeric impressions. They have also been using digitized scans and CAD/CAM devices in the fabrication of models, copings, frameworks, and restorations, primarily in the name of greater accuracy, consistency, and efficiency.

In a January 2008 survey, 48% of dental laboratories in the United States reported using the services of a CAD/CAM outsource center.2 In the same survey, nearly half also expressed interest in obtaining a CAD/CAM system, nearly 40% expressed interest in obtaining CAD/CAM scanner/design software, and nearly 30% expressed interest in obtaining digital impression devices. Those percentages have increased in the 2.5 years since the survey largely as a result of the systems’ improving quality, capabilities, and cost effectiveness.

Even the two CAD/CAM systems the authors presented in their previous article have recognized the importance of integrating their dental office apparatus with the technology and expertise available in the dental laboratory. These devices allow dentists to take digital impressions, design and then mill the restorations, and stain and glaze or simply polish the finished product, all in a single visit. Nevertheless, not all dentists have the confidence, desire, and time availability to design, mill, and characterize restorations for the digital impression scans they obtain on their patients.

Sirona, the company that manufactures the CEREC system, offers the CEREC Connect portal through which the dentist can take a digital impression and transmit the data to a dental laboratory within Sirona’s network. In turn, the laboratory can manufacture the dental restoration and return it to the dentist for insertion at a second patient visit.

Sirona also offers dental laboratories the inLab System, an array of CAD/CAM equipment and software that enables the technician to fabricate restorations from data providing virtual or actual working models. This year Sirona introduced the inEos Blue digital scanner as part of the inLab family of products, enabling even the laboratory to scan poured models and to either fabricate restorations in-house or upload the data files to Sirona’s infiniDent central production facility.

Similarly, D4D Technologies, creators of the E4D Dentist system, offers dentists the ability to transmit data from digital impressions to a dental laboratory for the fabrication of a finished restoration. The company’s suite of products for dental laboratories, the E4D Labworks™ system, features a handheld scanner for Rapid Scan™ touchless and clickless scanning. E4D Clone™ enables the technician to precisely copy the preoperative, diagnostic, or provisional model and duplicate it exactly in the final ceramic restorations.

The company also offers the Design On Site™ remote service, through which, for a nominal fee, a dentist can permit an experienced restoration designer at D4D’s Texas facility to access data files on the dentist’s E4D unit and design a restoration, so that the dentist can mill the restoration in-house and still provide the finished product for the patient in a single visit.

The two dedicated impressioning systems discussed in the previous article continue to provide the dentist with the ability to capture highly accurate digital impressions and to provide durable resin models either by a milling process (Cadent iTero) or stereolithically (3M ESPE Lava C.O.S.).

Prior to milling the master model, iTero affords the dentist three levels of laboratory interface: With the first level, Analog™, laboratories only receive models and iTero technicians do all of the digital margin review. Lab On-Line™, the second level of laboratory interface, offers the laboratory the opportunity to review the dentist’s cases online and order .STL export files. The third option is Full Lab CAD Station™, which gives the laboratory the ability to review, edit, and approve the digital model file prior to milling, along with the capability to export a .STL file. These three options provide an opportunity for the laboratory technician to have as much input in the scan review process as desired.

With 3M ESPE’s Lava C.O.S., the dentist now has the option of indicating the position of the margin line on the screen image of the preparation to assist the laboratory technician in the event of an indeterminate margin. The impression data file can be uploaded to the dental laboratory where, if the technician perceives a problem with the preparation, the dentist can be informed so that a correction can be made and an amended digital impression can be made and submitted. More than 600 dental laboratories are now part of 3M ESPE’s broadening Lava Network.

Dental laboratories have become conversant and experienced in digital technology. In addition to the four systems above, the availability of newer digital imaging devices, such as Wings DWOS™ (Zahn Dental/A Henry Schein Company, www.henryschein.com), Dental Scanner™ (Maestro 3D, www.maestro3d.com), and 3Shape D700 Impression Scanner (CadBlu Dental, www.cadbludental.com), have enabled dental laboratories to complement the impressioning technology available to dentists to create a synergistic workflow.

Easing Integration into the Dental Practice

In just the past few years, the leading digital impressioning systems have undergone major improvements that have enabled them to be more user-friendly and have broadened the scope of indications for their use.

Sirona’s CEREC Bluecam system now employs a shorter-wavelength blue LED (Figure 1) for capturing digital images, which, the company claims, creates a greater depth of field in the optical impressions. When combined with increased computing power, the result is greater accuracy at the preparation margins. The blue light is the same LED that is in the inEos Blue digital desktop scanner used by the dental laboratory.

The CEREC Bluecam AC (Acquisition Center) now works with enhanced CEREC 3D software to create digital impressions of entire quadrants, and even full arches (Figure 2). The new software also allows the dentist or assistant designing the crown to visualize right on the screen image the polychromatic block that may be used for esthetically demanding restorations, so that it can be adjusted according to need.

In addition, Biogeneric™ software proposes a recommended restorative design based on the natural morphology of even a single intact tooth. The software informs the dentist if the design proposal for the restoration exceeds the minimal allowable thickness for the material being used. The software also allows for buccal registration in addition to bite registration and is now capable of scanning impressions.

Sirona provided another first for the dental industry by recently launching CEREC meets GALILEOS. By combining a CEREC CAD/CAM scan with GALILEOS 3D X-ray data, surgical and prosthetic implant planning is integrated to achieve a compelling result: higher quality of treatment and time-saving workflow.

Improvements created by D4D Technologies in the E4D Dentist system in the past several years include enhancement of the DentaLogic™ software’s Autogenesis™ (Figure 3) capability to mimic the surrounding anatomical details of neighboring dentition in the restoration design.

With this and other enhanced capabilities, dentists and dental assistants at most E4D installations do the entire design and fabrication process on their own. When they have larger or more complex cases, or are just pressed for time, they have additional options, such as the Design On Site™ program allowing for remote design of a restoration by a skilled designer. D4D also provides a Support On Sight™ process in which a customer support team of clinical, software, and hardware experts responds to customer inquiries via toll-free telephone or e-mail at the dentist’s convenience. In addition, the company’s unique remote-access capabilities enable it to assist customers directly on their own E4D Dentist systems.

With the dentist’s permission, a customer support representative can remotely access the E4D system and restoration files. The representative can observe while the operator scans and designs or can even offer assistance in the design process, and help diagnose issues as he or she looks at each step in the design process and pinpoints the origin of any problem the operator is encountering.

D4D Technologies is presently working on E4D Compass, an integration of digital impressions taken by the E4D scanner with cone beam technology to create 3D images and physical models to enable the dentist to design and fabricate surgical guides, abutments, and restorations for use in cases involving the placement and restoration of implants.

A revolution in dental techniques will be realized when optical coherence tomography (OCT) is merged with CAD/CAM dentistry. Proprietary to D4D Technologies and possibly only a few years away, it will eliminate the retraction process from the impression step—allowing lasers to “see through” hard and soft tissue non-destructively and without harmful radiation.

Since introducing the iTero in 2007, Cadent has developed several key upgrades to allow for easier integration into the dental practice. iTero can now capture and articulate up to full-arch scans with all of the teeth prepared for restorations. Dentists can also elect to do a reference model scan and have a study model milled for treatment planning.

With large, full-mouth restorative cases, laboratory technicians used to have to mount the cases in stone on fully adjustable articulators. This step, in addition to being time-consuming, also added an additional potential for human error and discrepancies between the mounted casts and the actual bite. iTero has worked with Denar® (Whip Mix Corporation, www.whipmix.com), Stratos 300 (Ivoclar Vivadent, www.ivoclarvivadent.com) (Figure 4), and Panadent™ (Panadent, www.panadent. com) articulators to create iTero adapters that allow the SLA models to snap into the fully adjustable system, similar to the iTero articulator, thus removing the need to hand-mount casts if a specific type of articulator is desired. The indications for use of the iTero for crown and bridgework have expanded to not only accommodate inlays, onlays, crowns, and bridges of any length, but also veneers and even implant abutments.

Cadent is working in conjunction with several cone-beam CT companies (including Imaging Sciences International [www.imagingsciences.com] and Gendex [www.gendex.com]) and third-party software companies such as Anatomage (www.anatomage.com) to enable the systems to work synergistically in the treatment planning, surgical guide fabrication, and restoration of dental implants (Figure 5).

3M ESPE, the world’s largest manufacturer of elastomeric dental impression materials, has clearly recognized the direction in which digital technologies have taken the art and science of impressioning. Not only does the company manufacture blocks for the milling of CEREC and E4D restorations, it owns a share of D4D Technologies (as do Henry Schein Dental and Ivoclar Vivadent) and owns outright the Lava C.O.S. system.

As a part of a group of users testing and validating new indications, the authors, in their practice, were able to take digital impressions including the palate and buccal vestibules with the Lava C.O.S. in order to provide one patient with a full maxillary immediate denture and a second patient with two gold crowns, two porcelain-fused-to-metal crowns with semi-precision attachments, and a maxillary semi-precision removable partial denture ( Figure 6, Figure 7, Figure 8, Figure 9, Figure 10, Figure 11 and Figure 12 ). The company is doing more validation and testing before formally releasing full and partial dentures to its already extensive range of indications.

Integration through Education

The proper and thorough education of the dentist and involved members of the dental team in the use of digital impressioning systems is paramount for each of the companies that have been presented in this article. Basil Haymann, founder and chairman of D4D Technologies, has stated that, “there is no way we are providing anyone a system without having them (and their team members) complete the E4D Elements course that is included as part of the system—proper education is that critical.” The other companies would agree that training is critical to success with their products.

All of the companies involved in dental impressioning train the dentists and dental team members who will be using their systems in multiple-day courses, often at the company’s headquarters. In addition, most of them provide integrative training in the dentist’s own office with an experienced clinical trainer guiding the team through their first few cases. Beginner, intermediate, and advanced courses are offered by the manufacturers, often at major dental meetings and at gala “events” where system users learn advanced techniques and get a chance to share ideas with fellow customers. Lectures are offered online by most of the companies, and many of them offer newsletters and Facebook resources to enhance the dentists’ and team members’ learning experience.

The Bottom Line

Digital dental impressioning is a disruptive technological advancement that so surpasses the accuracy and efficiency of former techniques for obtaining replicas of prepared teeth for the purpose of fabricating restorations that its adoption by dentists is rapidly eclipsing the use of elastomeric impression materials.

The ultimate goals of dentists dedicated to quality restorative dentistry are to make their treatment of patients as accurate, stressless, and efficient as possible. The companies that have developed systems to help dentists achieve these goals are constantly enhancing the precision and scope of indications of their products to improve the quality of the dentistry provided.

References

1. Birnbaum NS, Aaronson HB, Stevens C, Cohen B. 3D digital scanners: a high-tech approach to more accurate dental impressions. Inside Dentistry. 2009;5(4):70-77.

2. CAD/CAM & Tech Census Survey. Dental Lab Products. December 2007.

About the Authors

Nathan S. Birnbaum, DDS, CAGS(Prosth)<, Associate Clinical Professor, Tufts University School of Dental Medicine, Boston, Massachusetts

Heidi B. Aaronson, DMD, Clinical Instructor, Tufts University School of Dental Medicine, Boston, Massachusetts


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