Abstract
Objectives. Digital impressions are increasingly used and have the potential to avoid the problem of inaccurate impressions. Only a few studies to verify the accuracy of digital impressions have been performed. The purpose of this study was to compare the marginal and internal fit of 3-unit tooth supported fixed dental prostheses (FDPs) fabricated from digital and conventional impressions. Methods. Ten FDPs were produced from digital impressions using the iTero system and 10 FDPs were produced using vinyl polysiloxane (VPS) impression material. A triple-scan protocol and CAD software were used for measuring and calculating discrepancies of the FDPs at 3 standard areas: mean internal discrepancy, absolute marginal gap, and cervical area discrepancy. The Mann-Whitney U test was used for analyzing the results. Results. For conventional and digital impressions, respectively, FDPs had an absolute marginal gap of 147 μm and 142 μm, cervical area discrepancy of 69 μm and 44 μm, and mean internal discrepancy of 117 μm and 93 μm. The differences were statistically significant in the cervical and internal areas (P < 0.001). Significance. The results indicated that the digital impression technique is more exact and can generate 3-unit FDPs with a significantly closer fit compared to the VPS technique.
Highlights
The lost wax technique is being rapidly replaced by computeraided design/computer-aided manufacturing (CAD/CAM) techniques in dentistry and dental technology [1], and the quality and fit of these restorations need to be evaluated
The results indicated that the digital impression technique is more exact and can generate 3-unit fixed dental prostheses (FDPs) with a significantly closer fit compared to the vinyl polysiloxane (VPS) technique
The conventional impression technique suffered a major complication for one FDP that had to be remade, since the FDP could not be seated on the corresponding study cast due to serious misfit
Summary
The lost wax technique is being rapidly replaced by computeraided design/computer-aided manufacturing (CAD/CAM) techniques in dentistry and dental technology [1], and the quality and fit of these restorations need to be evaluated. A mean marginal gap of 100 μm has been regarded as clinically acceptable [4,5,6,7]. A new technique for 3D fit evaluation has been proposed by Holst et al [8], using a triple scan protocol to obtain detailed information of component precision in all spatial orientations. The technique allows specific areas to be evaluated and the absolute marginal gap to be measured. This is not the same as the mean marginal gap since it includes the under- and/or overextension of the crown as well as the marginal gap [2]
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