The use of a 3D laser scanner using superimpositional software to assess the accuracy of impression techniques

Objective. Several studies have made comparisons in the dimensional accuracy of different elastomeric impression materials. Most have used two dimensional measuring devices, which neglect to account for the dimensional changes that exist along a three-dimensional surface. Purpose. The aim of this study was to compare the dimensional accuracy of an impression technique using a polyether material (Impregum) and a vinyl poly siloxane material (President) using a laser scanner with three-dimensional superimpositional software. Materials and methods. Twenty impressions, 10 with a polyether and 10 with addition silicone, of a stone master model that resembled a dental arch containing three acrylic posterior teeth were cast in orthodontic stone. One plastic tooth was prepared for a metal crown. The master model and the casts were digitised with the non-contacting laser scanner to produce a 3D image. 3D surface viewer software superimposed the master model to the stone replica and the difference between the images analysed. Results. The mean difference between the model. and the stone replica made from Impregum was 0.072 mm (SD 0.006) and that for the silicone 0.097 mm (SD 0.005) and this difference was statistically significantly, p=0.001. Conclusions. Both impression materials provided an accurate replica of the prepared teeth supporting the view that these materials are highly accurate. (C)0 2004 Elsevier Ltd. All rights reserved.