October 2012, Volume 33, Issue 9
Published by AEGIS Communications
Digital Impressioning Making Its Way into Dentistry’s Mainstream
The age of digital dentistry is here, and there is no denying that the integration of digital technology into dental practices has elevated the standard of care. Digital x-rays reduce radiation exposure while, with the aid of software, enabling practitioners and patients to see radiographs in greater detail. Digital cameras offer laboratory and patient communication tools that allow dentists to quickly share information via the Internet with laboratories and on computer screens with patients. Computerized axial tomography (CAT)-scan technology makes placing implants more predictable. Even digital smile designing is emerging as a communication tool with laboratories, specialists, and patients. It is no surprise that digital impression-taking is a quickly expanding market in the dental industry as more dentists adopt the technology.
The Importance of a Good Impression
Dental impression materials have a long history of innovation, from plaster of Paris in the early 1800s1 to hydrocolloids, addition silicone, polysulfides, polyether, and polyvinylsiloxane. The market is saturated with numerous impressioning products featuring attributes that facilitate capturing surface details using materials of different consistencies, settings, and working times. The proliferation of products used to capture impressions in the oral environment illustrates the importance dentists and laboratory technicians place on this procedure. Impressioning can be a high-stress situation for dentists; after being in.complete control of every step leading up to the process of capturing an accurate impression of their handiwork, they must hope for the best, right at the most critical moment.
Clinical methods for better impressions range from various types of hemostasis, different tray types, one-cord and two-cord techniques, use of lasers and electrosurges, and employing different consistencies or more hydrophilic impression materials. However, two basic principles for achieving great impressions hold true regardless of the modality used: there must be good preparations with crisp margins and healthy gingival tissue.2 Yet, sometimes dentists remove the impression tray from the patient’s mouth and carefully scrutinize the impression details, only to find themselves baffled by discovering that there is a void on the margin of the prepared tooth but nowhere else in the impression. Even when a perfect impression is captured, there is still work to do when the indirect restorations.come back from the laboratory, because there are no guarantees that all the chemical processes—with their inherent issues—are worked out. Clearly, there must be a better way.
The techniques for impression-taking with elastomers and creating stone models have been in widespread use since 1937.3 The first polyether material used for dentistry was introduced by the ESPEcompany in 1965. Despite all the inherent difficulties, impression-taking using elastomeric materials has been a staple of dentistry for 75 years.
Digital Impression Materials and Methods
Impression and scanning systems were introduced to dentistry in the mid 1980s, and in a June 2009 survey conducted by Dental Products Report, more than 16% of general dentists claimed to have some type of digital impressioning device in their practices.4 Many predict that in the next 5 years, most dentists in the United States and Europe will be using digital scanners for taking impressions.5 In orthodontics, digital impression-taking has been used successfully for years with systems like Cadent iOC/OrthoCAD (Cadent, Inc., www.cadentinc.com), OrthoPlex (DENTSPLY GAC International, www.gacorthoplex.com), SureSmile (Stratos/Orametrix, www.orametrix.de), and EMS RapidForm (Engineering & Manufacturing Services, Inc., www.ems-usa.com).
With the development of new high-strength esthetic restorative materials, such as lithium disilicates and zirconium, laboratory techniques have been developed whereby master models obtained from a dentist’s elastomeric impressions are digitally scanned to create stereolithic models on which restorations are fabricated. However, even with this high-tech laboratory innovation, it is clear that data obtained directly from 3-dimensional (3-D) digital scans of teeth using in-office digital scanners create more accurate stereolithic models.6
Digital impression systems offer a multitude of benefits over traditional impressions, including the ability to view the preparation magnified on acomputer screen. Similar to being able to review a digital camera picture immediately after it is taken and change the camera settings to improve the quality of the picture, a practitioner can evaluate the preparation and impression and make necessary changes before the restoration is fabricated—with no voids on the impression margins. Practitioners gain the ability to do one-visit indirect restorations with in-office systems, see the occlusion, and get accurate restorations created from digital models. There is also the potential for cost-sharing of the equipment with a laboratory. Models are fabricated from very hard materials with tolerances in the microns that will not chip or wear away; dies are cut to fit without any wiggle.7 Moreover, the digital impression process is far more pleasing to patients than traditional impressioning.
Perhaps the greatest benefit for dental laboratory technicians and dentists in adopting digital technology lies in the elimination of the many chemical processes involved in the treatment and manufacturing cycle of materials, and the many associated errors that can occur. These processes include curing the impression material, plaster, and base, and curing the investment material in restoration dies, as well as the retraction or shrinkage of conventional ceramic materials. Also, taking a bite to record interocclusal distance, which is normally done with impression materials, can be achieved digitally with nothing between the teeth. This dramatically reduces the risk of an inadequate interocclusal relationship. Esthetic full-mouth rehabilitations are being impressed digitally and transmitted to the laboratory for fabrication of ceramics with accurate results.8,9
While the positive traits are numerous, digital impressioning has its drawbacks as well. The use of a digital impression system may save time and money, but its high purchase cost is one of the main reasons for slow adoption of the technology. Another drawback is the steep learning curve to adopt the new technology, although mostcompanies offer support to new users. In some instances it is difficult for scanners to read the impressions, and there can be no undercuts in the preparations.
Since digital impressioning began in 1985 with CEREC® (Sirona Dental Systems, LLC, www.sirona.com), there has been a proliferation of digital impression systems that vary according to whether they are used as CAD/CAM devices in-office or as a dedicated impression system for in-office scanning and image transmission to a laboratory. Practitioners interested in digital impressioning for the office need to decide whether they want the responsibility of milling the ceramics in the office or leave that to a skilled laboratory technician. Systems are available (ie, CEREC 3D, Sirona; and E4D Dentist, D4D Technologies, www.E4D.com) that allow the purchase of the image-acquiring device separate from the CAD/CAM unit, with the option to add it at a later date.
The choice must also be made regarding the technology for the digital impression-capturing device, and whether to go with a closed or open architecture system. Image-acquisition devices use their own unique technology to capture images of the teeth and mouth. All modern systems capture mouth and preparation details that allow for excellent-fitting restorations, with the potential for fewer adjustments and remakes than traditional impressions. Laboratories love this, and some will even help their dentists with the purchase of a system in exchange for their laboratory work. While most capture still pictures that are spliced together to create a 3-D image, one system utilizes video to capture the impression.
With the numerous advantages of digital impressions over traditional impressions and the ability to benefit from digital impression-taking and/or CAD/CAM, more and more dentists are purchasing digital impression systems. It will likely be a routine procedure in most dental offices in the near future, as dentists, laboratory technicians, and patients all reap the benefits.
1. Weslcott A. The use of plaster of Paris for taking impressions of the month: Its history and importance. Dent Cosmos. 1870;12(4)169-181.
2. Cranham J. Making accurate master impressions. Inside Dentistry. 2012;8(6)62-68.
3. Sears AW. Hydrocolloid impression technique for inlays and fixed bridges. Dent Dig. 1937;43:230-234.
4. Birnbaum N. The revolution in digital impressioning. Inside Dentistry. 2010;6(7):114.
5. Birnbaum N, 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.
6. Polido WD. Digital impressions and handling of digital models: The future of dentistry. Dental Press J Orthod. 2010:15(5):18-22.
7. Freedman M, Quinn F, O’Sullivan M. Single unit CAD/CAM restorations: A literature review. J Ir Dent Assoc. 2007;53(1)38-45.
8. Weston JF. Conservative full-mouth reconstruction of a worn dentition utilizing digital impression technology and modern ceramic materials. Compend Contin Educ Dent. 2011;32(7):44-51.
9. Ender A. Mehl A. Full arch scans: conventional versus digital impressions—an in-vitro study. Int J Comput Dent. 2011;14(1):11-21.
10. Schoenbaum TR. Dentistry in the digital age: an update. Dent Today. 2012;31(2):108-113.
About the Author
Jason Olitsky, DMD
President, Florida Academy of Cosmetic Dentistry
TallahasseeFlorida; Clinical Adjunct Faculty
Arizona School of Dentistry and Oral Health
For more information, read Stand-Alone Scanning Systems Simplify Intraoral Digital Impressioning at dentalaegis.com/go/cced242
Visit Compendium’s Special Report page online, or go to dentalaegis.com/go/cced241. The page features exclusive video.commentary on impressioning from Dr. Louis Rose, editor-in-chief, as well as an online archive of Special Reports on a range of topics.