Clinical Parameters Influencing the Accuracy of 1- and 2-Stage Impressions: A Randomized Controlled Trial

Purpose: The clinical success of fixed restorations is linked to the precise reproduction of the prepared teeth by dental impressions. The hypothesis under examination was that neither clinical parameters nor the impression technique influenced the reproduction of the finishing line during impression making. Materials and Methods: For 48 patients who needed a fixed restoration, a 1-stage putty-wash, 2-stage putty-wash, and monophase impression were made after preparation in a randomized order. Clinical parameters (Plaque Index, probing depth, bleeding on probing, Gingival Index, location of the finishing line, bleeding during impression taking, and blood at the impression) were recorded. Master casts were manufactured and optically digitized. Using the data of the 1-stage putty-wash impression as reference, the reproduction of the finishing line was measured 3-dimensionally. Linear models were used for statistical analysis. Results: The finishing line was reproduced most precisely by the 1-stage putty-wash technique. Variables with significant influence were the impression technique, blood at the impression, and probing depth. The 2-stage putty-wash impressions showed significantly reduced accuracy compared with the 1-stage impressions. Conclusion: Clinical parameters and the impression techniques determine the reproduction of the finishing line. The benefit of 2-stage putty-wash impressions with regard to a more complete rendering of subgingival finishing lines should be questioned in light of these results.