Dimensional Changes "in vitro" from the Single- and Double-phase Impression Techniques with Addition Silicone in Partial Fixed Prosthodontics

Objectives: observation of the dimensional change of the single and double phase impression techniques with the addition silicone. Methods: a master model was cast from a hemi arch simulating a prosthodontics partial fixed with two abutments (45 and 47) with occlusal round perforations with a distance of 19,9985mm between them. With a workable tray (aluminium), 20 moldings from the master model were performed, divided in two groups: GU (10 molds by the single impression technique) and GD (10 moulds by the double phase impression technique), being the control represented by the measure of the master model. The molds obtained in the GD and GU groups as well as the master model were taken to a tridimensional coordinate measure machine with the precision of 0,5µm; the measures were taken among the centers of the reference round perforations. Results: no significant statistics differences were found between the GU (M = 19,989, DP = 0.0473) and the GD (M = 19.914, DP = 0,0660) groups. IC = 95%. Conclusions: a) the addition silicones didin´t show significant statistic differences at dimensional alteration between single and duble phase impression techniques; b) when comparing each technique separately with the master model measures, it was verified a shorter dimensional alteration at the single impression technique.