Digital Versus Traditional Impressions:
An Objective Discussion
Dental impressions provide the foundation for all restorative treatments. Used in treatment planning and laboratory fabrication, accurate impressions are essential for all parties involved—patients, dental professionals, and laboratory technicians. However, the task of achieving accurate impressions can present many challenges with regard to techniques and materials. While debate over material selection is ongoing, most dentists agree that the use of correct technique remains the most important factor in creating ideal impressions.1 Proper material preparation, retraction cords, material mixing, application, and setting time all affect the accuracy of an impression. Additional challenges include capturing the correct margins and details, maintaining patient comfort, and obtaining accurate occlusion records.
Nearly 50 years ago, polysulfides, a labor-intensive and ill-tasting solution, were introduced as the first elastomeric impression material.2 Another development, polyether material, demonstrated excellent hydrophilic qualities and great flow, but exhibited poor taste, relatively low tear strength, difficulty in mixing, and rigidity upon removal.1,2 In the 1970s, further material innovation addressed the challenges with polyether impression materials.2 Vinyl polysiloxane (VPS) materials displayed excellent tear strength, neutral taste, flexibility upon removal, and great dimensional stability, but were extremely hydrophobic.2 Currently, new vinyl polyether silicone combines the benefits of VPS and polyether materials, with excellent tear strength and dimensional stability from VPS, and wettability and flow from polyethers.
The development of digital dental impression systems provides an alternative. Demonstrating increased accuracy and efficiency, digital impressions contribute to better-fitting and more anatomically correct restorations.3 With the ability to visualize preparations almost immediately, digital impressions create a feedback tool for dentists, helping them to achieve higher-quality restorative designs.4
With digital impression-taking, patients and dental professionals avoid the traumatic and stressful impression-taking procedures that can occur with traditional materials. Use of oral scanners, compared to traditional methods, reduces patient discomfort and limits gag reflex because oral scanners avoid the soft palate.5 Overall, digital impressions provide convenience with no need for impression material, shipping, model storage, or model sterilization.5 Digital impressions diminish a dental office’s environmental “footprint” by reducing the need for impression trays, materials, and storage, along with decreased overhead costs and inventory.4 However, digital impressions have some limitations, including scanner size, the ability to capture only what the scanner can see, and decreased effectiveness when blood, saliva, or contamination are present in the oral cavity.
Traditional impression materials require minimal initial costs, as the average conventional impression with stock tray costs between $18 and $35.4 Conversely, digital impression systems necessitate a substantial upfront investment, costing on average anywhere between $20,000 and $30,000.6 Not only do they require the initial investment for the system, they also entail time to learn the system and train staff on proper use.5
The average cost per digital model varies and depends on whether the system is rented or owned and how often it is used. However, the case-management improvement and time-savings ability are the true advantages.6 Digital impressions demonstrate excellent margin capture and visibility, enable faster restorations, facilitate quick fabrication, and contribute to a minimal need for occlusal adjustment in final restorations.4 Compared with conventional impressions, digital impressions require less time and provide improved accuracy. A caveat is that not all digital impression systems work with all software systems and specific laboratories, so each practice considering this investment should research the best options to suit its needs. However, similar to digital x-rays, digital impressions are here to stay.
Suitability for Implant Treatment
Until recently, dental implant treatment planning required traditional impression materials to capture the location of the implant. However, with new partnerships between implant companies and digital scanner manufacturers, successful digital sensor systems for use in implant treatments are now available.7 In 2011, the US Food and Drug Administration approved systems for use in capturing digital impressions of coded healing abutments for implants.5 With this technology, digital impressions eliminate the need for impression copings. Now, various arrangements of facets on the occlusal surfaces of the abutments identify the implant platform diameter, the healing abutment height, the hex position of the implant, and the diameter of the emergence profile.5
With digital impressions, using 3-dimensional imaging, it is possible to plan precise guided-surgical placement and achieve more predictable results.5 In addition, oral scanner technology allows the implant information and abutment design to be simultaneously sent to the final abutment milling or laboratory facility for fabrication, or to an additional facility for a rapid prototype model of the abutment.5 Then, the dental laboratory can fabricate the definitive restorations. While both conventional and digital impressions provide the information for abutment fabrication and implant placement, digital impressions can be used for all treatment options, including single crowns to full-arch restorations, veneers, implants, inlays, and onlays.6
Managing Impression-Taking in Practice
For both digital and traditional impressions, the most important consideration to save money is getting the impression right the first time. Accurate impressions save chairtime at seating, reduce the incidence of remakes, and help achieve patient satisfaction. In addition, maintaining patient comfort facilitates continued treatment and the potential for referrals. Effective communication between a dental practice and the laboratory resulting from instantaneous and more detailed impressions also helps save time and money.
Whether shipping or electronically sending the impressions, accurately and efficiently relaying information regarding the case reduces the chances for mistakes, enhancing efficiency, productivity, and profitability. Continuation of staff education on impression-taking techniques also helps increase efficiency and expertise, reducing the need for remakes.
Digital and traditional impressions offer unique benefits and challenges. For patients with extensive bleeding, conventional impressions are best, because a digital scanner cannot detect what it cannot see. Digital impression systems, however, can potentially save about 30 minutes per treatment.6 Therefore, researching and understanding all the options for traditional and digital impression-taking allows dentists to make the right decision for his or her practice.
The addition of a digital impression system to a dental practice remains a large investment. Digital systems provide convenience and a reduced margin of error, but also present a high initial investment and learning curve. With today’s technology, all restorative impressions, including those for implant treatment, are possible with digital technology and traditional materials. Although in 3 to 5 years most impressions will probably be performed digitally, conventional impressions will still have a place.
1. Burgess JO. Impression material basics. Inside Dentistry. 2005;1(1):30-33.
2. Brown RL Jr. An elastomeric impression material breakthrough. Dentistry Today Web site. http://www.dentistrytoday.com/restorative/impression-materials/1313. Accessed February 5, 2014.
3. Birnbaum NS, Aaronson HB. Digital dental impressions systems. Inside Dentistry. 2011;7(2):84-90.
4. Radz GM. Clinical impressions of digital impressions. Dent Economics. 2009;99(3):68-73.
5. Digital impressions of coded implant abutments. Inside Dentistry. 2011;7(8):110.
6. Mitchem C. Why digital impressions? Dent Economics. 2012;102(1):32,54,88.
7. Stover J. Case study: restoring implants with digital impressions. Dental Compare Web site. http://www.dentalcompare.com/Featured-Articles/135066-Case-Study-Restoring-Implants-With-Digital-Impressions/. Accessed February 5, 2014.
ABOUT THE AUTHOR
Stephen Poss, DDS
Poss Dental Designs, Brentwood, Tennessee