Can transfer type and implant angulation affect impression accuracy? A 3D in vitro evaluation

Impression accuracy is fundamental to achieve a passive fit between implants and the superstructure. Three transfer types were tested to evaluate the differences in impression accuracy and their efficiency in case of different implant angles. A master model with four implant analogues placed at 0 degrees, 15 degrees and 35 degrees was used. 27 impressions were taken with three different types of impression coping: closed tray technique coping (CT), open tray technique coping (COT) and telescopic open tray coping (TOT). The impressions were poured. Analogues were matched with scan bodies to be scanned and exported in STL. An implant bar was designed from each STL and another one from the master model. A comparison between these bars was obtained. Linear and angular measurements for every type of coping were calculated for different angulations. The collected data were analyzed with ANOVA test (95% of confidence). Student's t test showed a significative discrepancy (p <= 0.001) on linear and angular measurements on Delta x, Delta y, Delta z with different transfer types as well as diverse implant positioning angles (p <= 0.001). Within the limitations of this study, it can be concluded that the coping type and the implants divergence may be significant parameters influencing the impression accuracy.