Effect of impression materials and techniques on the marginal fit of metal castings

The effect of two impression materials used in three different techniques was tested for the accuracy of the marginal fit of metal castings. Sixty identically prepared Ivorine teeth were divided into groups of 20. The following methods were selected to make impressions: (1) putty in a metal stock tray with simultaneous elastomeric impression wash, (2) copper band relined with autopolymerizing acrylic resin and subsequent light-body elastomeric impression material, and (3) copper bands with modeling compound. Faciolingual sections of the Ivorine teeth with cemented metal castings were examined by scanning electron microscopy (SEM) at x 100 magnification. Measurements of the thickness of cement layers were calculated both manually and by use of a recently developed computerized method. The differences in the gingival marginal gaps between various impression materials and techniques at both the facial and lingual surfaces were not statistically significant.