Dimensional Accuracy of Two-Step Impressions Relined with Extra-Light Addition Silicone Material

Alireza  Jafari; Esmat  Mombeini; Leila  Payaminia; Elaheh  Beyabanaki; Rahim  Tahmasebi

doi:10.18502/fid.v21i17.15550

Alireza Jafari Department of Prosthodontics, Dental School, Bushehr University of Medical Sciences, Bushehr, Iran
Esmat Mombeini Private Practice, Ahwaz, Iran
Leila Payaminia Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran
Elaheh Beyabanaki Department of Prosthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Rahim Tahmasebi Department of Biostatistics and Epidemiology, School of Health, Bushehr University of Medical Sciences, Bushehr, Iran

DOI: https://doi.org/10.18502/fid.v21i17.15550

Keywords: Dental Impression Materials; Dental Impression Technique; Tooth Preparation, Prosthodontic; Silicones

Abstract

Objectives: Some small defects may remain in the impression after making a two-step putty-light body impression. The aim of this study was to evaluate and compare the dimensional accuracy of 2-step and relined 2-step (3-step) putty-light body impressions.

Materials and Methods: In this in vitro study, 30 impressions were made with putty, light body, and extra-light body addition silicone materials using the 2-step and 3-step impression techniques (N=15). An epoxy resin master model was made duplicating a maxillary typodont with left first premolar and first molar teeth prepared with a shoulder finish line and truncated pyramidal-shaped indices in the mid-palate and third molar sites. In addition to creating a reference digital model by scanning the master model, 30 master casts were scanned to produce digital models. The anteroposterior (AP) and cross-sectional (CS) dimensional accuracy of the models were compared with the master model using linear measurements. Moreover, tooth size measurements were made and compared using the root mean square (RMS). Two-sample t-test was applied to analyze the data (α=0.05).

Results: The mean AP and RMS differences between the two study groups were not significant (P>0.05). However, the CS difference between the two groups was significant (P<0.001), and the 3-step impression technique showed smaller discrepancies in comparison to the master model.

Conclusion: There was no significant difference in accuracy of the two techniques for single-unit and multiple-unit preparations. The 3-step impression technique had a higher CS dimensional accuracy.