![]() ![]() The inaccuracy of these analog materials and procedures suggested that greater predictability may lie in digital technology. Some of the distortions observed are of clinical significance and likely to contribute to a lack of passive fit of any superstructure. The retarder was used by two dental schools in the USA to provide students with extended working times in a teaching Australian Dental Journal 1998 43:6. The impression plaster displayed cumulative distortion, and the PVS putty with light body showed the least reliability. The polyether material proved to be the most reliable in terms of predictability. Although there was no significant distortion between the impressions and the master model or between the impressions and their casts, there were distortions between the master model and the master casts, which highlighted the cumulative effects of the distortions. The PVS monophase material reproduced the master model most accurately. Statistical analyses indicated that distortion occurred in all of the impression materials, but inconsistently. The positions of the implants on the master model, the impression copings, and the implant analogs in the subsequent casts were measured using a coordinate measuring machine that measures within 4 μm of accuracy. Five impressions were made with each impression material and cast in die stone under strictly controlled laboratory conditions. The impression materials used were impression plaster (Plastogum, Harry J Bosworth), a polyether (Impregum Penta, 3M ESPE), and two polyvinyl siloxane (PVS) materials (Aquasil Monophase and Aquasil putty with light-body wash, Dentsply). The master model was a stainless steel model with five implant analogs. The study was motivated by the knowledge that distortions can occur during impression making and the pouring of casts and that this distortion may produce inaccuracies of subsequent restorations, especially long-span castings for implant superstructures. Purpose: The purpose of this clinical study was to compare a recently introduced fast-setting polyvinyl siloxane (PVS) impression material with heavy body/light body (HB/LB) combination (Imprint 4 3M ESPE) (experimental group) with a conventional PVS impression material with HB/LB. ![]() The purpose of this study was to compare the capacity of different impression materials to accurately reproduce the positions of five implant analogs on a master model by comparing the resulting cast with the stainless steel master model. Statement of problem: Impression making is a challenging clinical procedure for both patients and dentists. ![]()
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