Both the groups involved impression recording using splinted (Subgroup I) and nonsplinted impression copings (Subgroup II). Group A used hexed open-tray impression copings and Group B used nonhexed open-tray impression copings. ![]() The groups were divided into two main groups of 40 samples each. All impressions were recorded using open-tray impression technique. A reference master model based on All-on-4 implant concept with two parallel (implants 1 and 2) and two angulated (implant 3 at 17° and implant 4 at 30°) was fabricated using implant angulation guide. Factors which affect impression accuracy include implant angulation, impression material, impression copings, technique, and splinting.Ī sample size of 80 study models fabricated from the impression of different groups was included. Precise fit of a fixed implant-supported prosthesis depends on the accuracy of the implant analog location within the definitive cast. The critical aspect is to record the three-dimensional location of the implant in bone rather than reproducing fine surface details. The aim of this study was to evaluate and compare the accuracy of hexed and nonhexed pickup impression copings with and without splinting using polyether (PE) and polyvinyl siloxane (PVS) impression materials in open-tray technique in recording multiple straight and angulated implant positions.Īn accurate impression results in an accurate definitive cast, thus minimizing the incidence of prosthesis misfit. ![]() Understanding of the magnitude and variability of distortion when employing certain impression-making methods and impression coping shapes helps the clinician to select a better implant component and impression technique. The impression coping shape had more impact on impression inaccuracy than impression technique did. Less inaccuracy occurred in less retentive shape impression copings (Replace Select) compared with the more retentive one (Implantium) (p(r). These measurements (linear and rotational displacements) were compared with the measurements calculated on the reference resin models that served as control, and data were analyzed with a two-way analysis of variance at α = 0.05. Impressions were poured with type IV stone, and the positional accuracy of the implant replica heads in x-, y-, and z-axes (represented in ) and also rotational displacement (ΔΘ) were evaluated using a coordinate measuring machine (Mistral, DEA Brown&Sharpe, Grugliasco, Italy). Matching implant replicas were screwed into the impression copings in the impressions. ![]() Twenty medium-consistency polyether impressions of these models were made with square and conical impression copings of each system using open-tray and close-tray techniques. Two reference acrylic resin models (Technovits 4000, Heraeus Kulzer GmbH & Co., Wehrheim, Germany) with five internal connection implants having different shapes of impression copings (Implantium and Replace Select ) were fabricated. This in vitro study compared the accuracy of two different impression techniques with two different impression coping shapes using polyether impression material to obtain precise definitive casts. Consequently, the restoration may require corrective procedures. Movement of impression copings inside the impression material using an open-tray or close-tray impression technique during clinical and laboratory phases may cause inaccuracy in transferring the three-dimensional spatial orientation of implants intraorally to the definitive cast. Accurate recording of implant location is required so that definitive restorations are properly supported and do not place additional stresses on the implants.
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