Objectives: The long term success of a crown is strongly influenced by its marginal fit, which in turn is closely related to impression taking. In addition the quality of the impression is directly influenced by clinical parameters. The aim of this in-vitro study was to compare the attainable marginal fit, using two different impression techniques as well as two methods of gingival retraction. Methods: To simulate clinical conditions 6 teeth each in 10 lower jaws of freshly slaughtered cows were prepared with infragingival finishing-lines. Two different retraction techniques were used to expose the finishing-line: Retraction cords (Surgident/Sigma Dental Systems-Emasdi) and electrosurgery (Electrosurgical device MD 62/Martin) was applied contra-laterally at 3 teeth per quadrant. Two impressions per jaw were taken in a two-step putty-wash technique (TPW) and in an one-step putty-wash technique (OPW), respectively, using Imprint II Quick Step (3M-Espe). On the casts (Fuji-rock/GC) metal copings (Phantommetall/Degussa) were fabricated. Each coping was seated on the (extracted) original tooth and the marginal discrepancies were measured with a Leica M 420 microscope at 8 reference marks per tooth at 40x magnification. Because the data were not normally distributed, the results were subjected to non-parametric statistics (Mann-Whitney U-test; p=0.05). Results: Overall marginal discrepancies ranged between 0 and 200 µm. There was no significant difference between electrosurgery and gingival retraction cords. There was a small but significant difference (p<0.05) between the two impression techniques (TPW mean: 30 µm, interquartil range: 17-40 µm; OPW mean: 40 µm, interquartil range: 25-59 µm). Conclusions: Within the limits of the study it can be concluded, that the use of gingival retraction cords as well as electrosurgery lead to acceptable results. The difference between TPW and OPW concerning the marginal discrepancies is clinically insignificant.

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