Objectives: Disposable impression-trays are gaining popularity for prosthodontic treatments. However, very little information is available about their impact on the accuracy of the impression. It was therefore the aim of this study to evaluate the accuracy of impressions taken with disposable plastic impression-trays (PITs; Borderlock/ClanBV) in comparison to metal stock-trays (MSTs; Schreinemakers/ClanBV) with four different impression materials in a standardized in-vitro setup. Methods: A master-model was fabricated, consisting of four cylindrical test-abutments fixed on a metal plate and completed with an acrylic mask to an upper jaw model. Each test-abutment had a central mark and two corresponding flat areas for measurements. The master-model and the impression-trays were fixed in a Zwick1454 testing device (Zwick-Roell) to standardize the impression procedure. 10 two-stage putty-wash impressions per group were taken using Panasil Putty, Panasil Binetics Putty (Kettenbach), Provil Novo Putty and Provil Novo Putty Soft (Heraeus Kulzer) combined with their corresponding wash material using the PITs. 10 impressions taken with Panasil Putty using MSTs served as control. Stone models were poured >1h after impression taking and stored for 7 days prior to measuring the diameters of the test-abutments (DTU) and their overall distances (OD). Data were subjected to non-parametric statistics (U-Test: p=0.05). Results: Average discrepancy of DTU ranged from -0.5 to -1.75 %, while average discrepancy of OD ranged from 0.08 to 0.2 % compared to the master-model. The MST-group showed significantly lower deviation from the master-model than the corresponding PIT-group (DTU: p<0.05). Significant differences were observed between the pvs-materials (DTU: p<0.05). Conclusions: Within the limits of the study it can be concluded, that MSTs lead to more accurate impressions than PITs. However, accuracy with the PITs tested seems to be acceptable from the clinical point of view in the case of full-crown preparations.

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