Purpose Traditionally several impression materials and techniques utilizing custom tray with a window have been proposed to record excessively movable tissues. These procedures are meant to produce very minimal if not no compression of the tissues during the process of impression to avoid any tissue distortion. Although studies have shown compression on tissues can be minimized, a technique that can completely eliminate the pressure is not proven. This study focuses on comparing accuracy of impression techniques that use common impression materials which produce minimal tissue displacement using digital intra oral scan as a reference. Materials and methods This is an in vivo clinical study on a cohort of 14 edentulous patients that presented with excessively movable tissues. An intra oral scan of the edentulous ridge was obtained using Medit i700 scanner (Medit Corp, Seoul Korea). Final impressions were made in light body vinyl polysiloxane (Dentsply Sirona Milford, Delaware) after the tissues were border molded with Type 1 modelling plastic compound (Kerr Corporation, Orange, CA) in a conventional custom tray and a custom tray with a window (Zahn, Melville NY). The impressions were scanned using 3Shape D2000 (3M Shape Copenhagen, Denmark) desktop scanner. These files were imported into Geomagic Control X software (Geomagic Control X; 3D Systems, Rock Hill, SC). The STL (standard tessellation language) files of final impression with conventional tray and tray with a window were aligned to the intra oral STL scan file using best fit alignment. The areas of interest (anterior region, palate and tuberosity) were delineated for three-dimensional comparison. Root mean square (RMS) values describing deviations in impression techniques were obtained and compared using Two-Way ANOVA followed by Tukey HSD posthoc analysis. Each subject served as their own control as the study compared tissues recorded with 3D surface scans to impressions using vinyl polysiloxane. A p<0.05 was considered significant. Results There was no significant difference in the RMS values between the two impression techniques that used conventional tray and tray with a window studied in terms of their deviation from the intra oral scan (p=0.56). However, there was significant difference between the areas tested in terms of deviation from the intra oral scan (p=0.0049). The tuberosity area in the open tray impression showed deviation with a mean difference of -0.12 RMS value when compared to the anterior area in the closed tray impression (p=0.002). The anterior area in the closed tray impression showed deviation with a mean difference of +0.1012 RMS value when compared to the palatal area in the closed tray impression (p=0.013) Finally, the anterior area in the closed tray impression showed deviation with a mean difference of 0.106 RMS value when compared to the tuberosity area in the closed tray impression (p=0.01). The Tukey HSD posthoc analysis demonstrated that there was no significant difference between all other groups (p>0.05). There was also no significant interaction between impression technique and area (p=0.46). Conclusion There were no significant differences in the tissue displacement when final impressions made with conventional closed tray and tray with a window were compared to intra oral scan. However, there were significant differences in tissue displacement between areas compared in a conventional closed tray, where anterior area consistently showed more displacement compared to palate and tuberosity. Lastly there was no significant interaction between the two variables impression technique and areas. Therefore, final impression in a custom tray with window can minimize displacement of excessively movable tissues in comparison to a conventional closed tray.