INFLUENCE OF DOUBLE IMPRESSION TECHNIQUE BY ELASTOMERS IN REPRODUCIBILITY OF FULL EDENTULOUS ARCHS

Abstract

This study aimed to evaluate the fidelity of functional gypsum models of completely edentulous arches obtained from impressions made with condensation silicone and polysulfide. The conventional single-impression technique was compared with the double-impression technique, involving relining of the first layer. For this purpose, impressions were taken from standard maxillary and mandibular completely edentulous arch models, with standardization of the mold/model position during the procedure using a metallic device. The experimental groups were established considering the following factors: single or double impression techniques using condensation silicone (Xantopren XL) or polysulfide (Permlastic), resulting in eight groups with five samples each. The obtained molds were poured with type IV dental stone (Zero Stone – Dentona), following the manufacturer’s recommendations regarding material proportion and manipulation. Standardized procedures for mold disinfection and model storage were also adopted until the time of measurements. The dimensional stability of the gypsum models was assessed by measuring predetermined points represented by three metallic spheres fixed to the alveolar ridge crest region—one in the anterior region and two bilaterally in the posterior region—which were reproduced in the molds. These spheres served as reference points for determining an occlusal plane using a three-dimensional coordinate measuring machine (3D Hexagon Global). The comparison of results was based on the areas obtained and point-to-point distances, with the data subsequently subjected to two-way ANOVA statistical analysis, considering a significance level of 5%. The results demonstrated no significant differences in dimensional changes among the experimental groups of the maxilla and mandible, regardless of axis, number of layers, or material used. In the maxilla, only the material variable showed statistical significance (p<0.05), with silicone exhibiting superior performance. It was concluded that the evaluated materials presented satisfactory dimensional stability, even when applied in two layers, supporting the feasibility of using this technique for functional impressions of completely edentulous arches.