New theoretical model to measure pressure produced during impression procedure for complete dentures - Visual inspection of impression material flow

Objective: A theoretical model, based on fluid dynamics, was developed to measure impression pressure. The purpose of this study was to evaluate the validity of this theoretical model by comparing its theoretical analysis against actual pressure measurements conducted using an impression tray and edentulous oral mucosa analog embedded with pressure sensors. Methods: In the theoretical model, a hollow tube was mounted onto an impression tray by penetrating through the tray. When force was applied to the tray, pressure was produced which then caused the impression material to flow into the hollow tube. Length of impression material which flowed into tube was denoted as l. In the calculation formula for theoretical model, pressure impulse I was expressed as a function of impression flow length l. For actual pressure measurements, four electric pressure sensors were embedded in an experimental edentulous arch. To visually observe and measure length of impression material flow, four transparent silicon tubes were mounted vertically at different positions on tray. During tray seating, impression material flowed into tubes and pressure which caused material flow movement was measured by the embedded sensor at each tube's position. Results: Based on actual pressure measurements under one experimental condition, regression analysis of pressure data acquired from electric sensors yielded the formula, Y = 0.056X² + 0.124X. Based on theoretical analysis using a particular viscosity value, the numerical formula yielded was Y = 0.057X², which resembled that of the regression formula. Significance: Theoretical model presented in this paper augured well for clinical application as an easy and economical means to examine magnitude and distribution of impression pressure by measuring lengths of impression material flow in tubes fixed to impression tray.