Effect of different impression techniques and elastomeric impression materials on the dimensional accuracy of partially edentulous mandibular arch

Rafael Pino Vitti,Adriano Relvas Barreira De Oliveira,Mário Alexandre Coelho Sinhoreti

doi:10.20396/bjos.v15i3.8649995

Abstract

Aim: Evaluate the dimensional accuracy of stone casts of a partially edentulous mandibular arch made by two impression techniques (1-step putty/light-body and 2-step putty/light-body) using addition and condensation silicones. Methods: A partially edentulous steel stainless cast with four markings on teeth 33, 37, 43, and 47 was used to obtain the impressions. The transverse (33-43 and 37-47) and anteroposterior (33-37 and 43-47) distances were measured by measuring microscope (30x magnification; 0.5μm accuracy). For the 1-step putty/light-body technique, both viscosities of the impression materials were handled together. For the 2-step putty/light-body technique, the impression materials of different viscosities were handled separately and a polypropylene spacer (2 mm thick) was used to create a relief. The same distances were measured om stone casts (n = 5). The values were submitted to normality test (Kolmogorov-Smirnov) and analyzed statistically by three-way ANOVA and Tukey’s (5%). Results: All distances showed shrinkage (negative linear changes). The addition silicones showed better accuracy than condensation silicones (p<0.05) and no significant difference was found between the impression techniques (p>0.05). The edentulous zone (43-47) presented worst dimensional accuracy results. Conclusions: The accuracy of the castsis more related to the impression material than impression technique.

Highlights

Impression technique is a frequently performed procedure in the dental office that requires selection of an appropriate impression material[1]
The results of this study showed that addition silicone provided greater accuracy in the stone casts and greater reliability in impression structures than condensation silicone in both impression techniques evaluated
These results are consequence of the excellent physical and mechanical properties of the addition silicone, such as no formation of byproducts during and after the set reaction by the terminal group ethylene or vinyl with hydride groups[11,16]. These properties provide the obtainment of more than one accurate stone casts from the same mold due to excellent elastic recovery[17] and tear strength of the addition silicone[18]

Summary

Introduction

Impression technique is a frequently performed procedure in the dental office that requires selection of an appropriate impression material[1]. Dental impression presents a negative imprint of buccal structures[2]. In Dentistry there are four groups of impression materials: polysulfides, polyethers, condensation, and addition silicones. These materials present four viscosities: putty- (type 0), heavy(type 1), medium/regular- (type 2), and light-body (type 3). For the clinical use the most important difference between these materials is their dimensional stability[8]. Factors such as viscosity, hydrophilicity, thickness, soaking, polymerization shrinkage, incomplete elastic recovery of the impression materials, type of the adhesive used in tray, pouring time, thermal shrinkage between buccal cavity and room temperature[9] may affect the dimensional accuracy of the molds

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Results

Conclusion