three-dimensional accuracy of different impression techniques for dental implants

background: accurate impression making is an essential prerequisite for achieving a passive fi t between the implant and the superstructure. the aim of this in vitro study was to compare the three-dimensional accuracy of open-tray and three closed-tray impression techniques. materials and methods: three acrylic resin mandibular master models with four parallel implants were used: biohorizons (bio), straumann tissue-level (stl), and straumann bone-level (sbl). forty-two putty/wash polyvinyl siloxane impressions of the models were made using open-tray and closed-tray techniques. closed-tray impressions were made using snap-on (stl model), transfer coping (tc) (bio model) and tc plus plastic cap (tc-cap) (sbl model). the impressions were poured with type iv stone, and the positional accuracy of the implant analog heads in each dimension (x, y and z axes), and the linear displacement (δr) were evaluated using a coordinate measuring machine. data were analyzed using anova and post - hoc tukey tests (α = 0.05). results: the δr values of the snap-on technique were signifi cantly lower than those of tc and tc-cap techniques ( p < 0.001). no signifi cant differences were found between closed and open impression techniques for stl in δx, δy, δz and δr values ( p = 0.444, p = 0.181, p = 0.835 and p = 0.911, respectively). conclusions: considering the limitations of this study, the snap-on implant-level impression technique resulted in more three-dimensional accuracy than tc and tc-cap, but it was similar to the open-tray technique. key words: dental implants, dental impression materials, dental impression technique