Ex vivo digital comparison of four impression techniques using an industrial laser scanner

Introduction: The aim of the study was to compare different impression techniques used for fixed prosthodontics. Methodology: A master cast with prepared abutments was created from polymethyl-methacrylate (PMMA). A high-resolution industrial scanner was used to create a virtual reference model. Four different impressions were made, three with polyvinyl-siloxane (PVS) (n = 10 for each): one-step putty-wash (1SPW), two-step putty-wash prepared with an escape channel (2SPW-Ch), two-step putty-wash with a polyethylene spacer foil (2SPW-Fo), and one with polyether monophasic technique (MP) from the PMMA model and digitized with an industrial scanner. The stereolithographic (STL) files of the impressions (n = 40) were exported. Each file was compared to the reference using the Geomagic Verify software. Six points were assigned to enable virtual calliper measurement of tooth diameters and distances of varying sizes within the arch. Results: In the case of die diameters, the deviation from the mould ranged from 31.84 to 180.64 μm. At the stump diameter level, the MP and 1SPW techniques showed significantly more minor differences than the 2SPW-Ch, and the MP was significantly more accurate