March 2011, Volume 7, Issue 3
Published by AEGIS Communications
With four digital systems currently on the market, more are on the horizon as dentists embrace new technology.
By Andrew C. Koenigsberg, DDS | Paul Feuerstein, DMD
Digital impression systems are a hot technology that more dentists are incorporating into their practices. Up until about 5 years ago, this technology was synonymous with the first fully CAD/CAM system, Sirona Dental Systems’ (www.sirona.com) CEREC®software, distributed exclusively by Patterson Dental Supply, which has now been on the market for 25 years. Today, there are three other digital systems being used in the dental marketplace, with a few more on the horizon. Currently, there are Cadent’s (www.cadentinc.com) iTero, the Lava™ Chairside Oral Scanner C.O.S. from 3M ESPE (www.3mespe.com), both of which are digital impression systems only; and the E4D Dentist System, which is a complete CAD/CAM system produced by D4D Technologies (www.e4dsky.com) and distributed by Henry Schein, Inc (www.henryschein.com).
In 2007, a two-part article the co-author wrote in this publication1,2 detailed a variety of systems available at the time, and offered a look into the future. Four years later, the same four systems are still being actively marketed, although all have undergone several upgrades, which will be explained in this article. These systems are similar in that they all can take digital impressions of teeth. Each takes a different approach to the acquisition process, but each system ultimately yields clinically acceptable digital files that can be used to fabricate restorations. Two of the systems, CEREC and E4D, have the ability to design and fabricate restorations in the office. All four can send this digital file to a dental laboratory for fabrication of any conventional or CAD/CAM restorations.
Over the last 25 years, CEREC (Figure 1) has evolved into an Acquisition Center (AC) with patented Biogeneric restoration design software. In simple terms, the acquisition has changed from infrared to a blue LED, and the need for manual image capture with a foot pedal has been eliminated. Also, because of the algorithm that Sirona uses, very few images are required if the acquisition wand is placed directly over the occlusal, which captures the margins in that view.
To simplify the export of the digital impression files to a dental laboratory, Sirona developed CEREC Connect. Laboratories with the CEREC software and CEREC®inLab equipment can take these files and construct full restorations, copings, frameworks, or physical models. The latter is useful for the clinician who wants full-gold, porcelain-fused-to-metal or other hands-on laboratory restorations, as opposed to CAD/CAM ceramic/composite restorations. This is one of two systems, along with E4D, that allows the clinician to fabricate a final restoration in the office. Advances from “block” manufacturers such as Vident (www.vident.com), Ivoclar Vivadent (www.ivoclarviavdent.us), and 3M ESPE now yield restorations that are multicolored or have internal dentin layers that rival natural teeth. There are now more robust materials that allow more delicate inlays and onlays with high strength. Sirona has also simplified the restoration design by using an algorithm called Biogeneric, which looks at the adjacent teeth for design. This is in contrast to the previous design technique, which used a library of tooth forms.
E4D Dentist (Figure 2) has moved ahead with a variety of new features to make the scanning, designing, and milling process simpler for the entire dental team. E4D has SOS (Support on Site), which allows remote access to the support team at D4D Technologies to every E4D owner. D4D Technologies has a team of laboratory technicians, dental assistants, and hardware and software experts who, with a simple phone call, can take over the E4D System in the office via remote access and help the practitioner design or troubleshoot a case in real-time. E4D also offers a design service (Design on Site) that allows the dentist to simply take the digital impression and upload it to E4D for expert design. The system designs and sets up the restoration, then electronically sends that information directly to the milling center in the office, as if there is an in-office technician. Of course, many dentists choose to do all of their own design, which the new software from E4D makes quite simple. The software’s intuitive design tools include a unique view called ICE (I See Everything), as well as “design and mill” ability for multiple adjacent units. In addition an entire E4D Sky™ Network is being set up that will allow every E4D owner to upload his or her case to authorized laboratories or design centers with the click of a mouse.
iTero continues to improve its software and scanning capabilities as well (Figure 3). Using a small touch probe that needs no powder or reflective liquid, the system allows the operator to place the camera right on the tooth, and yields consistently accurate impressions. The system also has a digital voice that guides the operator through scans and gives “advice” related to occlusal clearance and other parameters. This system does not currently have an in-office milling center, but easily exports the digital file to the practitioner’s central offices, allowing a physical model to be milled. This model can be sent to virtually any dental laboratory to fabricate all restorations. There are also affiliated laboratories that can take the digital files and use them directly in the laboratory CAD/CAM machines. The exported files are “open” and can be used with almost any software or hardware.
3M ESPE also continues to improve the Lava C.O.S. and simplify the capture (Figure 4). Because the system uses streaming video, stopping is not required in order to acquire an image. A dusting of powder is necessary, however, to give the camera “speckles” that help it “see” the tooth structure. The misconception with this system—as well as CEREC—is that the entire surface has to be powdered, which of course would change the dimensions of the preparation. Both companies address this issue during mandatory training. The operator can view and review the digital models on the screen using 3D glasses, which aid in determining the accuracy and margins of the scans and preparations. This system does not have an in-office milling center. Instead, files are exported to 3M’s facilities, where a robust resin model is made via stereolithography that can be used to create conventional restorations. Partner laboratories can use the files to create CAD restorations, such as 3M ESPE’s own Lava™.
These systems’ ability to review and critique the impression and the preparation prior to sending it to the laboratory or milling center is a great advantage over conventional impressions. All of the systems allow for instant “retakes” of areas that might have been missed, and also allow re-preparation and a quick and simple retake of the preparation without having to retake the entire impression.
Practitioners taking traditional impressions try to avoid telling patients that they need “just one more,” and experience at least one moment of angst when removing the tray from the mouth and peering into the mold to ensure everything is captured. All of these systems are developing methods to take digital scans of an impression. There are still certain circumstances in which a standard impression has to be taken, even when the practitioner would prefer the digital workflow. CEREC and E4D currently have this capability, and can send that file to the milling center.
From a clinical perspective, there are many advantages to digital impressions.
After a short learning period, it is possible to routinely take quadrant impressions with the opposing arch and occlusal registration in under 2 minutes.
Accuracy of Articulation
With the “Buccal Bite” feature it is possible to view the interdigitation of the teeth while the occlusion is being registered. An additional advantage over elastic “bite” materials is that there is no “bounce” when articulating the arches—a frequent problem when using conventional materials. Furthermore, the occlusal contacts can be viewed for the entire quadrant as a check that arches are in the proper position.
With digital impressions, the dentist must immediately approve the model and draw the margins. Inadequate areas can be identified and quickly corrected with preparation modification and additional images. This is significantly easier and more effective than evaluating and retaking impressions. It is also critically important for ceramic restorations, which have stricter design requirements than metal restorations. Preparation guidelines must be strictly adhered to and impressions must be 100% readable. Indeed, laboratories have reported that up to 50% of impressions are inadequate. Digital impressions allow the dentist to regain control over preparation evaluation and the quality of the entire model, a major source of remakes and poor restorations.
Along with CAD/CAM software and a milling unit, digital impressions allow for single-visit restorations. When properly integrated into the office workflow, this is more efficient for both the patient and the dentist.
Most patients strongly prefer the digital imaging process to that of conventional impression taking. It is faster, and gagging, choking, and claustrophobia are generally not issues.
New Ceramic Materials
Many new ceramic materials—zirconium, for example—can only be fabricated through digital design. Other materials, such as lithium disilicate and multi-shaded veneering porcelains, are more efficiently fabricated on digital models. Sending the laboratory a physical impression increases cost and the probability of error.
Faster Laboratory Turnaround
Laboratories can start working on digital impressions before the patient has even left the dental office, which significantly reduces the time between appointments.
Because there are no materials to be stored and mixed, digital impressions and models have less variability than conventional impressions and models. Most clinicians and technicians recognize that a restoration made from one set of impressions and models will rarely be a perfect fit for models made from a second impression.
Cases are submitted online and automatically tracked, so communication with the laboratory is simplified, and there is no pickup to be arranged and logged.
Prescriptions are standardized so that laboratories get the information they need. Additionally, dentists and laboratories can jointly view cases online, so decisions can be made without shipping models or partial cases back and forth.
Digital impressions are easy to save and even easier to find if a case must be retrieved in the future. Often a restoration can be remade with the click of a button.
Dentists can expect the use of this technology to grow significantly in the coming years, given the advantages of digital impressions and younger practitioners’ comfort with digital technology. Although there are some significant costs, strategic financing and incentives with reduced associated fees make these units affordable. The additional ROI is peace of mind knowing that there will be no call from the dental laboratory about missed margins or other impression errors, and being sure about the consistency of fit at insertion. Although improvements are constantly being made, thousands of completed restorations verify that this technology is here now.
The author is a current consultant for 3M ESPE, Cadent, E4D, and Sirona.
1. Feuerstein P. New changes in CAD/CAM: Part 1. Inside Dentistry. 2007;3(2):84-86.
2. Feuerstein P. New changes in CAD/CAM: Part 2. Lab Systems. Inside Dentistry. 2007;
About the Authors
Andrew C. Koenigsberg, DDS
New York, New York
Paul Feuerstein, DMD
North Billerica, Massachusetts