This summary is based on the article published in The Journal of Prosthetic Dentistry: Digital versus conventional impressions for fixed prosthodontics: A systematic review and meta-analysis (August 2016)
In the fabrication of fixed multi- or single unit dental restorations, the accuracy of marginal and internal fit are integral to the long-term success of the crowns. Discrepancies in the internal fit can adversely affect the seating of the crown as well as the marginal fit. Typically, an impression captures the restorations’ margins and their internal aspects. Nowadays, impressions can be made using conventional impression materials such as polyether or polyvinyl siloxane or via a digital impression which then through the use of CAD-CAM technology helps to create a milled final restoration.
This review compared the marginal fit and internal fit of fixed restorations which were fabricated using conventional impressions with those made using digital impressions as well as to assess the effects that various variables had on the accuracy of the fit.
- Restorations fabricated from conventional and digital impression techniques resulted in statistically similar discrepancies in marginal fit
- Digital dies had smaller internal and fit discrepancies when compared to dies made of SLA/polyurethane
- Fabrication techniques such as “pressing” and CAD-CAM resulted in similar discrepancies for both digital and conventional impression groups
- Metal alloy restorations fabricated digitally had a smaller marginal fit discrepancy compared to zirconia and glass ceramic restorations.
- Restorations made of glass ceramics had larger internal spaces when compared with zirconia and metal alloys across both impression techniques
- No statistically significant differences were noted in the marginal or internal fit of fixed dental prostheses and single crowns made using either impression technique
- The use of polyether or polyvinylsiloxane impression material resulted in similar measurement discrepancies in the restorations