Abstract
Several impression materials are available in the Brazilian marketplace to be used in oral rehabilitation. The aim of this study was to compare the accuracy of different impression materials used for fixed partial dentures following the manufacturers' instructions. A master model representing a partially edentulous mandibular right hemi-arch segment whose teeth were prepared to receive full crowns was used. Custom trays were prepared with auto-polymerizing acrylic resin and impressions were performed with a dental surveyor, standardizing the path of insertion and removal of the tray. Alginate and elastomeric materials were used and stone casts were obtained after the impressions. For the silicones, impression techniques were also compared. To determine the impression materials' accuracy, digital photographs of the master model and of the stone casts were taken and the discrepancies between them were measured. The data were subjected to analysis of variance and Duncan's complementary test. Polyether and addition silicone following the single-phase technique were statistically different from alginate, condensation silicone and addition silicone following the double-mix technique (p < or = .05), presenting smaller discrepancies. However, condensation silicone was similar (p > or = .05) to alginate and addition silicone following the double-mix technique, but different from polysulfide. The results led to the conclusion that different impression materials and techniques influenced the stone casts' accuracy in a way that polyether, polysulfide and addition silicone following the single-phase technique were more accurate than the other materials.
Highlights
Impression taking and pouring are critical steps in the process of producing successful crowns and bridges in oral rehabilitation
The mean and standard deviation of the discrepancies between the prepared tooth edges in the master model and in the stone casts are presented in Table 2 and Graph 1
The test embodied in the specifications provides good baseline data to compare materials, the testing conditions differ from those encountered during clinical practice; the master model used in the present study represented a partially edentulous mandibular right hemi-arch segment, a common situation in clinical practice
Summary
Impression taking and pouring are critical steps in the process of producing successful crowns and bridges in oral rehabilitation. Impression materials should reproduce hard and soft tissues around prepared and adjacent teeth in order to obtain biologically, mechanically, functionally and esthetically acceptable restorations.[1,2,3] There are some factors that affect definitive impression quality such as tooth preparation design, soft tissue management, tray selection, impression material and impression technique.[4,5]. There are several elastic impression materials available for dental use: synthetic elastomeric materials, including polysulfide, condensation silicone, addition silicone and polyether; and hydrocolloids.[6,7] All these materials are used for reproducing oral conditions in order to construct restorations. Some professionals have been using alginate in clinical practice for definitive impressions, problems with dimensional stability and unsatisfactory detail reproduction are some of the limitations to its use.[8]
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