Open and closed tray technique accuracy with two impression materials

Objectives: The accurate transfer of fixtures' position is an important step in fabricating implant-supported superstructures. This study compared the accuracy of polyether (PE) to polyvinylsiloxane (PVS) used in open and closed tray impression techniques in transferring direct and angled implants' position into stone models.

Methods: A stainless steel master model with 6 external hex implants (Nobel Biocare, Goteberg, Sweden), positioned from 1 to 6, was fabricated. The implants in the position 2 to 5 were placed perpendicular to model sheet, while those in the positions 1 and 6 were placed with respectively 15 and 30 degree angulations. 40 samples of gypsum type IV were randomly assigned to 4 groups of 10, in which the impressions were made following closed or open tray technique using custom trays with PE or PVS. The orientation of implants on master model and samples were evaluated by Coordinate Measuring Machine (CMM), and the differences were analyzed using two way ANOVA test.

Results:

The type of impression material (PE vs. PVS ) and the technique (open vs. closed tray ) did not significantly influence the direct implants position difference ( 0.002 / 0.005 ; P value > 0.05 ). The impression material type did not significantly influence the accuracy of transferring 15- and 30-degree angulated implants. ( 0.005 / 0.001; P value > 0.05).The accuracy of impression techniques was similar in 15-degree angulated implants ( 0.006; P value > 0.05). However, significantly more dimensional accuracy was observed in open-tray method than in closed tray (0.088; P value = 0.0001).

Conclusion:

Closed-tray impression technique is recommended due to the ease of the procedure, patient comfort and similar accuracy with the open-tray technique in equivalent circumstances. However, in implants with more than 15 degrees angulations, open-tray impression technique is preferred due to the more dimensional stability gained thereby