Displacement of Simulated Flabby Tissue by Different Tray Designs and Impression Materials

To compare the effect of 3 tray designs and 3 commonly used impression materials on the displacement of flabby tissue during maxillary edentulous impression by superimposition of 3D digital models.

Fifteen maxillary edentulous casts with simulated flabby tissue were fabricated by modifying a standard maxillary edentulous acrylic resin cast. Three types of impression trays were fabricated: trays with conventional relief, trays with additional relief, and trays with an open window. Three impression materials were tested: light-body polysulfide, light-body vinylpolysiloxane, and zinc oxide eugenol paste. For the analysis of tissue displacement during impression making, the test and control stone casts were scanned using a 3D laser scanner, and the 3D digital models were superimposed using metrology software. Statistical analyses were performed with an α = 0.05.

Negative deviations were recorded at the areas of the alveolar crest, posterior part of flabby tissue, and middle of the palate. On the other hand, a positive deviation was recorded at the area of the anterior part of flabby tissue. A significant difference in the displacement of flabby tissue was found when using different tray designs (p < 0.0001). The tray with the open window showed significantly low tissue displacement at the flabby tissue region. Depending on sites, the amount of flabby tissue displacement showed different significances by the different impression materials used (anterior part: p < 0.0001; alveolar crest: p = 0.097; posterior part: p < 0.0001). Conventionally relieved trays showed significantly higher values of displacement at the anterior part of flabby tissue (p < 0.0001), while trays with open windows showed similar values of displacement at all measuring points, and no significant differences among different impression materials were found (p = 0.104).

There were significant differences in the displacement of flabby tissue with different tray designs, especially with displacement occurring at the anterior and posterior parts of flabby tissue. Tray designs should be considered in order to make proper impressions when flabby tissue is present.