Investigation of the deviation during the information transfer from the prosthetic field to the laboratory scanners

Abstract

The aim of this work is to investigate the deviations during the first stage of the information transfer from the prosthetic field to the dental laboratory scanners for CAD/CAM technology. The first upper left molar on an artificial acrylic resin dental model was prepared for full metal-ceramic crown according to the standard guidelines for step cut. The prepared prosthetic field was scanned by a high-precision industrial scanner with a 1-mm ruby ball stylus and a digital copy was made. With a standard tray, a two-phase two-stage silicon (A-silicone Zhermack hydrorise putty and light body) impression from the acrylic model was taken following the technology recommended by the manufacturer. The impression was powdered with dental stone type IV and a stone model was created 1 h after impression, the time delay taking place ordinarily in dental practice. Using the same measurement methods, the stone model’s surfaces were digitized. Both digital models were compared using the acrylic resin dental model as a reference. The results on the deviation during the transfer of information between the prosthetic field and the stone model represent the first level of inaccuracy in the CAD/CAM processing technology. The difference in the alteration of each dimension according to the reference and the stone model is not more than 20 μm in shrinkage or expansion direction. Thus, the widely used approach for information transfer using stone models from the prosthetic field to laboratory scanner for CAD/CAM technology could be considered as relevant with an accuracy of about ±10 μm. If the silicon impression is performed carefully, the stone models are sufficiently accurate representations of the prosthetic field and their digitalization in the dental laboratory is a reliable starting point for the CAD/CAM technology.