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Clinical trial investigating success rates for polyether and vinyl polysiloxane impressions made with full-arch and
Glen H Johnson1, Lloyd A Mancl, E Ricardo Schwedhelm
1Professor, Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, WA 98195-7456, USA. gjohnson@u.washington.edu
Statement Of Problem:
Success rates for making fixed prosthodontic impressions based on material and tray selection are not known.
Purpose:
The purpose of this clinical study was to compare first impression success rates for 2 types of impression material and 2 impression tray systems.
Material And Methods:
Dual-viscosity impressions were made with a vinyl polysiloxane (VPS) (Aquasil Ultra Monophase/Aquasil Ultra XLV) and a polyether (PE) (Impregum Penta Soft HB/Impregum Garant Soft LB) impression material. The first impression made was evaluated for success or failure using developed criteria. Fifty senior dental students participated. The type of impression material alternated for each new patient. A full-arch perforated plastic (President Tray) or a plastic dual-arch impression tray (Tri-Bite) was used based on clinical guidelines. Impression success rates were compared using logistic regression, fitted using the method of generalized estimating equations (alpha=.05).
Results:
One hundred ninety-one impressions were evaluated, and the overall success rate was 61% for VPS and 54% for PE (P=.39). Additional regression analyses, adjusted for potential confounders, did not indicate a difference between the 2 systems (P=.35). There was little difference in success rates between the 2 materials when a full-arch tray was used (50% versus 49% success, P=.89), whereas a larger difference was apparent with the use of dual-arch trays (70% success with VPS versus 58% success with PE, P=.21). The most common critical defect was located on the preparation finish line (94%), and the most common operator error was inadequate gingival displacement (15%).
Conclusions:
There was little difference in success rates between VPS and PE when full-arch impression trays were used, but there was greater success when using VPS with dual-arch trays. For single teeth, the trend favored VPS, but when more than one prepared tooth per impression was involved, the success rate was higher for PE.
