Evaluation of the Effect of Distance Between Dental Abutments on the Accuracy of One-Step and Two-Step Impression Techniques With Polyvinyl Siloxane (PVS) Material.

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.