Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 14 1 2017 02 15 40 47 EN Ahmad Ghahremanloo Associate Professor of Prosthodontics Department, Mashhad Dental School, Mashhad University of Medical Sciences, Mashhad, Iran Mahdieh Seifi Assistant Professor of Prosthodontics Department, Mashhad Dental School, Mashhad University of Medical Sciences, Mashhad, Iran Jalil Ghanbarzade Associate Professor of Prosthodontics Department, Mashhad Dental School, Mashhad University of Medical Sciences, Mashhad, Iran Seyyed Mohammad Abrisham Assistant Professor of Prosthodontics Department, Yazd Dental School, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Rashid Abdolah Javan Statistical Advisor, Mashhad Dental School, Mashhad University of Medical Sciences, Mashhad, Iran 2015 11 03 2016 10 25 Objectives: The aim of this study was to compare the accuracy of dental implant impressions obtained by a combination of different impression techniques and viscosities of polyvinyl siloxane (PVS). Materials and Methods: Four parallel fixtures were placed between mental foramina in a master model of lower dental arch. Three different viscosities (putty/light body, medium body/light body, and monophase: heavy body) and direct and indirect techniques (six groups) were used, and seven impressions were obtained from each group (n=42). To measure the accuracy of impressions, drift, horizontal, and vertical angles of the implants, as well as the hex rotation of the implants in casts were evaluated using a digitizer device (1μm accuracy), in comparison with master arch. Data were analyzed using five-factor two-way ANOVA and Tukey’s post-hoc test. Results: The accuracy of impressions was assessed and the results showed that direct technique was not significantly different from indirect technique (P>0.05). Also, there were no significant differences between the mentioned viscosities except for the horizontal angle (P=0.006). Conclusions: Viscosity of impression materials is of high significance for the accuracy of dental impressions.   https://fid.tums.ac.ir/index.php/fid/article/view/830 https://fid.tums.ac.ir/index.php/fid/article/download/830/933