Accuracy of multi-unit implant impression: traditional techniques versus a digital procedure
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The objective of this study was to evaluate the accuracy of different impression techniques on multiple implants.
Material and methods
A master cast simulating a jaw with four implants was used.
Eight impression techniques were tested: open tray-polyether#1, open tray plus splint of impression copings with acrylic resin-polyether#1, closed tray-polyether#1, open tray-polyether#2, open tray-splint-polyether#2, closed tray-polyether#2, open tray-impression plaster, and digital impression (DI).
Five impressions of the master cast were taken with each traditional impression (TI) technique, pouring 35 sample casts. Three different clinicians took 5 DI each (n = 15).
A three-dimensional coordinate measurement machine (CMM) was used to measure implant angulation and inter-implant distances on TI casts. TI data and DI Standard Tessellation Language datasets were compared with the master cast.
The best and the worst impressions made with TI and DI were selected to fabricate four milled titanium frameworks. Passive fit was evaluated through Sheffield test, screwing each framework on the master cast. Gaps between framework-implant analogs were measured through a stereomicroscope (×40 magnification).
Statistically significant differences in accuracy were found comparing the different impression techniques by CMM (p < 0.01). DI performed the best, while TI techniques revealed a greater variability in the results.
Sheffield test revealed a mean gap of 0.022 ± 0.023 mm (the best TI), 0.063 ± 0.059 mm (the worst TI), 0.015 ± 0.011 mm (the best DI), and 0.019 ± 0.015 mm (the worst DI).
Within the limits of this in vitro study, the digital impression showed better accuracy compared to conventional impressioning.
The digital impression might offer a viable alternative to traditional impressions for fabrication of full-arch implant-supported prostheses with satisfactory passive fit.
KeywordsImpression accuracy Digital impression Intraoral digitizer Passive fit Full-arch Dental implants
The authors thank 3M ESPE for providing materials.
Furthermore, the authors wish to thank Prof. Fabrizio Barberis and Dr. Alberto Lagazzo (Department of Civil, Chemical and Environmental Engineering, University of Genova) for their assistance in data analysis.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
For this type of study, formal consent is not required.
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