Kyung Chul Oh

Purpose To retrospectively compare and analyze differences in tissue displacement of edentulous arches among three‐dimensional (3D) files obtained using various impression‐making techniques. Materials and Methods Fourteen patients who underwent prosthodontic treatment for edentulous arches at Yonsei University Dental Hospital between June 2020 and April 2023 were included in the study. Three types of 3D files were used for the evaluation of each arch: a 3D scan file of a definitive cast (Group DEF), a preliminary cast (Group PRE), and an intraoral scan file (Group IOS). The files were superimposed on a reference 3D scan file of the definitive cast group through best‐fit matching using metrology software. Seventeen measurement points (MP1‐4, RC1‐6, TB1‐2, and PPS1‐5 for the maxilla and RP1‐2, RC1‐7, BS1‐4, and LS1‐4 for the mandible) were selected for both the maxillary ( n = 13) and mandibular arches ( n = 6). The deviation considering the direction (DD) between the three groups and the absolute deviation (AD) between the three groups were recorded. Kruskal–Wallis and post‐hoc Mann–Whitney tests were used for statistical analyses (α = 0.05 and α = 0.0167, respectively). Results Concerning the DD values, at the RC4 point of the maxillary arch, Group PRE exhibited significantly higher values than Groups IOS ( p = 0.006) and DEF ( p < 0.001), and at the RC5 point of the maxillary arch, Group IOS exhibited significantly lower values than Groups PRE ( p = 0.016) and DEF ( p < 0.001). Group IOS showed significantly lower DD values in the mandibular arch than Group DEF at the RP2 and RC3 points ( p < 0.167). The AD values in Groups PRE and IOS significantly differed from those in Group DEF (all p < 0.001) at all measurement points but did not exhibit significant differences between each other ( p > 0.05). Conclusions Different impression‐making methods yielded different amounts of tissue displacement. The tendency of 3D files regarding tissue displacement varied at certain residual ridge crest areas and retromolar pad areas. The absolute amount of tissue displacement observed in the intraoral scan data was comparable to that observed in the preliminary casts.