Several recent studies compared crowns fabricated from current generation CAD/CAM systems with those from a conventional impression material and reported similar marginal fit.11-13 These studies demonstrate that impressions, models, and crowns fabricated from digital intraoral scanners were equally or more accurate than those produced from traditional impression materials. One area of limitation identified by laboratory studies is that not all systems produced comparable accuracy and precision of full-arch scans.14
The time required to make digital impressions compared to conventional impressions is controversial. Although the 3- to 5-minute scanning process requires roughly the same amount of time as traditional impression materials setting time (fast set is 2.5 minutes) there is no need to select a tray, apply tray adhesive, clean impression trays, assemble impression guns and tips, or disinfect impressions. There are still time-consuming steps associated with some digital impression systems, including wheeling the device to the operatory, plugging it in and loading the software. Additionally, the unit and wand require disinfection. Another time-saving feature of a digital impression compared to a conventional impression is that a portion of a deficient area may be re-scanned with the digital system rather than retaking the entire impression. Lee and Gallucci15 reported that the total treatment time for iTero digital impressions of single implant restorations was approximately half the treatment time of a traditional impression. A study by Ahrberg and colleagues16 reported saving approximately 5 minutes with digital impressioning of a quadrant and saving 1 minute 30 seconds with a full-arch tray. A controlled double-blind clinical study by Givan and colleagues17 reported no difference in 50 crown margins made from digital and conventional impressions. This study reported significantly higher impression time with iTero-produced digital impressions (8 minutes, 40 seconds) compared to fast-set traditional impressions (4 minutes, 23 seconds); however, conventional impression set-up and clean-up time were not included.
In the evolution of digital impression systems, some potential improvements remain. One obstacle that remains for all impression systems is management of soft tissue and oral fluids surrounding the crown margins. Development of high-resolution ultrasound technology for digital intraoral scanning would allow the scanner to “see-through” soft tissue and oral fluids.
Another area for improvement is integration of digital impressions with patient management software. When intraoral scans can be accessed in patient management software as easily as digital radiographs, the clinician may appreciate additional benefits of digital models for treatment planning and patient education. Additional efficiency could be achieved by making an intraoral scanner that could be plugged directly into the USB port of an operatory computer similar to a digital radiograph sensor.
Digital impressions offer advantages over conventional impressions by expediting the laboratory process, avoiding an uncomfortable conventional impression material, and allowing a magnified view of the preparation. Current studies suggest that digital impressions produce crowns as or more accurate than conventional impressions.6-13 More data must to be collected, however, to substantiate that digital impressions are more time efficient than conventional impressions.15-17
John O. Burgess, DDS, MS; Nathaniel C. Lawson, DMD, PhD; and Augusto Robles, DDS, MS, have received research/grant support from 3M ESPE.
About the Authors
John O. Burgess, DDS, MS
University of Alabamaat Birminghamc
Nathaniel C. Lawson DMD, PhD
University of Alabamaat Birmingham
Augusto Robles, DDS, MS
University of Alabamaat Birmingham
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6. Joda T, Brägger U. Patient-centered outcomes comparing digital and conventional implant impression procedures: a randomized crossover trial. Clin Oral Implants Res. 2015;26(4):1-5. doi: 10.1111/clr.12600.
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10. Ender A, Mehl A. Full arch scans: conventional versus digital impressions—an in-vitro study. Int J Comput Dent. 2011;14(1):11-21.
11. Abdel-Azim T, Rogers K, Elathamna E, et al. Comparison of the marginal fit of lithium disilicate crowns fabricated with CAD/CAM technology by using conventional impressions and two intraoral digital scanners [published online ahead of print June 19 2015]. J Prosthet Dent. 2015. doi: 10.1016/j.prosdent.2015.04.001. Accessed July 30, 2015.
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16. Ahrberg D, Lauer HC, Ahrberg M, Weigl P. Evaluation of fit and efficiency of CAD/CAM fabricated all-ceramic restorations based on direct and indirect digitalization: a double-blinded, randomized clinical trial [published online ahead of print June 14 2015]. Clin Oral Investig. 2015. http://link.springer.com/article/10.1007%2Fs00784-015-1504-6#page-1. Accessed July 30, 2015.
17. Givan DA, Burgess JO, O’Neal SJ, Aponte AA. Prospective evaluation of ceramic crowns by digital and conventional impressions. J Dent Res. 2011;90(spec iss a):380.
Digital Impression Showcase
Figure 1 | 3M True Definition Scanner
3M ESPE’s 3M True Definition Scanner delivers powerful 3D video–based scanning and provides precision, accuracy, and repeatability for taking digital impressions. The technology is contained in a small, ergonomic, lightweight wand.
Figure 2 | CS 3500
With the CS 3500 intraoral scanner, practitioners can easily acquire precise true color, 2D and 3D digital impressions. The CS 3500 works as part of the integrated CS Solutions CAD/CAM restoration portfolio or as a standalone solution in a practice’s restorative workflow.
Figure 3 | Planmeca PlanScan
Planmeca PlanScan captures the oral environment with a high level of precision. The two-piece cradle features a weighted base or it can be wall-mounted or separated to fit into a standard handpiece caddy.
Figure 4 | iTero Element
Align Technology Inc.’s iTero Element features industry-leading 3D imaging designed to capture 20 color scans per second. Scanned images appear instantly on the 19” high-definition multi-touch display.
Figure 5 | Dental Wings DWIO
Dental Wings dwio brings ease-of-use to a new level with its innovative design. The small, light handpiece allows the dentist to take digital impressions in a natural, fluid manner while focusing on the patient’s mouth.
Figure 6 | TRIOS
Shaped much like an operatory impression gun, TRIOS digital scanner balances firmly in the hand, providing steady control of the device. A unique autoclavable scanner tip allows the user to rotate the scan source from the mandible to the maxilla, capturing up to a quadrant in 25 seconds.
Figure 7 | CEREC AC with Omnicam
Sirona’s CEREC Omnicam’s revolutionary design features an ergonomic handpiece and special optics. It has a rounded camera tube that allows allows easy rotation of camera and offers easy-to-learn, intuitive, full-color scanning without powder or an opaquing agent.