OBJECTIVE: The aim of this study was to evaluate the effect of distance between dental abutments on the accuracy of one-step and two-step impression techniques with polyvinyl siloxane (PVS) material. MATERIALS AND METHODS: Four master models were fabricated with different interabutment distances equal to one, two, three, and four premolar lengths 1-4 (L1, L2, L3, and L4). Seven one-step impressions were taken from each master model using PVS impression material (Group A, n = 7). For two-step impressions, a 1.5 mm polyethylene spacer was used over each master model, and impressions were taken (Group B, n = 7). Scans from the casts were superimposed over the master model scans. Accordingly, differences were measured and compared with statistical tests (Kolmogorov-Smirnoff test, Mann-Whitney test, and Friedman's test) to evaluate the effect of interabutment distance within each impression technique group and also compare the one-step and two-step impression techniques. p value <
0.05 was considered statistically significant. RESULTS: A statistically significant difference was noted among the different edentulous areas in the one-step impression technique group (Group A, p = 0.010). At edentulous span, a statistically significant difference was recorded (p = 0.047) with two-step impression technique being more accurate compared to the one-step impression technique. Friedman's pairwise analysis in Group A demonstrated a significance between one premolar and four premolar interabutment distance groups (p = 0.006). CONCLUSION: The accuracy of the one-step impression is significantly affected by the increase in interabutment distance from one premolar to four premolar edentulous.