Three-dimensional accuracy of different impression techniques for dental implants

Abstract

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