Abstract
Two critical factors that influence the accuracy of an impression include the proper manipulation of the impression materials and the technique used to make the impression. The purpose of this study was to clinically evaluate the effect of different mixing techniques on the accuracy of vinyl polysiloxane (VPS) impressions by assessing metal framework fit of fixed partial restorations. The study included 92 consecutive patients diagnosed with partial edentulism and treated with fixed partial denture restorations. The mixing technique was one of the two following mixing methods: hand mixing technique (45 patients), with the putty material mixed according to the manufacturer’s instructions; or mechanical mixing technique (47 patients), with the putty material mixed by a Pentamix device. Under both mixing methods, vinyl polysiloxane was used as the impression material. Two impression techniques were randomly used by the operators (One/Two-stage putty –wash impression techniques). The accuracy of the metal framework restorations was tested clinically and radiologically, resulting in significant statistical difference (p = 0.04) between different mixing techniques. The mechanical mixing produced more accurate restorations (metal framework misfit only in 14.9% of patients vs. hand mixing 31.1%). Regarding the impression techniques, the two-stage impression technique was found to be significantly more accurate (p = 0.04), resulting in 14.6% ill-fitted metal frameworks vs. 31.8%, in the one-stage technique. It can be concluded that mechanical mixing yields more accurate impressions leading to more accurate restorations, especially when combined with two-stage impression technique.
Highlights
Impression accuracy significantly affects the quality of fixed partial denture marginal adaption, internal fit, interproximal and occlusal contacts [1,2]
The impression accuracy is mainly subjected to the effect of proper handling of the impression materials [13–19] and impression techniques applied [20–24]
The mixing techniques can be divided into two major categories: mechanical mixing and hand mixing techniques
Summary
Impression accuracy significantly affects the quality of fixed partial denture marginal adaption, internal fit, interproximal and occlusal contacts [1,2]. Restoration fit is an important predictor that determines the survival of fixed partial dentures due to its influence on plaque retention, caries rate and periodontal and pulpal health of the prepared teeth [3–7]. The impression phase is predominantly controlled by the clinician and may influence the restoration fit accuracy [8–12]. The impression accuracy is mainly subjected to the effect of proper handling of the impression materials [13–19] and impression techniques applied [20–24]. Previous studies have shown that different mixing techniques have a substantial effect on the quality of impressions and castings obtained [19,25]. The working time of impression material can be affected by the mixing technique [26]. The mixing techniques can be divided into two major categories: mechanical mixing and hand mixing techniques
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