Effect of Plastic Impression-Transfer Copings on the Dimensional Accuracy of Implant Impressions

Abstract

Purpose: The purpose of this in vitro study was to evaluate the effect of plastic impression transfer copings on the dimensional accuracy of close tray implant impressions.
 Methods: A master model was constructed using autopolymerizing acrylic resin. Five parallel holes were drilled for implant analogs. Custom impression trays were made with autopolymerizing polymethyl methacrylate resin. The study consisted of 2 groups (n=5): (group 1) Impression was obtained with using plastic impression transfer coping (group 2) Impression was obtained without using plastic impression transfer coping. Vinylpolysiloxane impression material was used for both groups. After the impression were obtained, casts were made by type IV dental stone. Casts were scanned with the lab-type scanner and transferred to the measurement program. Measurements were made from a specific reference corner for each analog to ensure standardization. Data were saved as millimeters and pairwise comparisons were made with Welch's t-test analysis.
 Results: The effect of plastic caps was evaluated by applying the t-test to each distance. For all distances, the distortion seen in the measurements taken without the cap is higher than the measurements taken with the cap, but no significant differences were found (p>0.05). 
 Conclusions: In the anterior-posterior distances, the distortions were found compression type, in the right-left distances the distortions were found as expansion-type. There is a dimensional change in the measurements taken without a cap, but no clinically significant differences were found.