| Summary: | When making a tooth-supported fixed prosthesis, an impeccable impression is required. Therefore, the gingival tissue around an abutment tooth needs to be temporarily retracted to enable the impression material to flow around the preparation margin. For years, the method of choice has been placing a cotton retraction cord into the gingival sulcus to make space for the impression material. In 2000, a new material, aluminium chloride paste (Expasyl®), was introduced, which was supposed to play the same role as the retraction cord. Until now, this paste has not been fully studied and has never been compared to the classic method. The aim of this randomized controlled clinical trial (RCT) is to evaluate the influence of three different methods for temporary tissue retraction before impression taking on the gingiva. Additionally, patients' perception of the intervention and technicians' evaluation of the impression material and easiness of the preparation of the master cast will be evaluated using a Visual Analogue Scale. Sixty-seven individuals in need of a tooth-supported reconstruction were included in the study and randomized into three equally large groups. In the first group (T1)only Expasyl® aluminum chloride paste was used to retract the gingiva. In the second group (T2)a retraction cord was inserted proximally and orally and Expasyl® was used as a second layer of retraction. In the third group (C) two retraction cords were used to retract the gingival tissue (the traditional double cord technique). This multi-center study took place at the Faculty of Odontology, University of Iceland, and in four private practices in Iceland. Clinical measurements were made at baseline and 30±10 days after cementation. To evaluate the gingival position, four study casts were taken at different stages: #1 just before impression taking, #2 before cementing the reconstruction, #3 immediately after cementation, and #4 was taken 30±10 days after cementation. Standardized photographs of the study casts were taken, the photographs ...
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