Background: Using appropriate impression materials and techniques guarantees accurate transfer of implant position and precise surface details of prepared teeth to the definitive cast. Different implant impression techniques including direct (open tray) and indirect (closed tray) techniques are commonly used. This technique is frequently indicated when there is limited inter-arch space or tendency to gag, or working in the posterior region of the mouth. A variety of factors may affect the accuracy of implant impressions such as different impression techniques, impression materials, tray type, the number of implants, angulation of implants or abutments and prosthetic connection features. Aim of the study: To compare accuracy of different implant impression techniques. Materials and methods: The present study was conducted in the Department Prosthodontics of the dental institutions. An edentulous maxillary cast with six implant analogues in the anterior region was used as the reference model. Two types of impression trays were used; they were (i) closed custom trays, and (ii) open custom trays. Two impression techniques were studied. They were: Group I - Polyvinyl siloxane impressions (putty and light body) and Group II - Polyether impressions (medium body). All the impressions were poured using the same quantity of Type IV dental stone. The casts were allowed to set for 1 hour before removal from the impression. Only one cast was formed from one impression. The casts were subjected to measurement after 24 hours to simulate clinical situation. Results: It was observed that the average dimensional errors in impressions with open custom trays in Group 2 were comparatively less as compared to Group 1. However, the dimensional errors were similar in group 1 and group 2 when impressions were made using closed custom tray. On comparing the results, it was found that the results are statistically non-significant. Conclusion: Within the limitations of the present study, impressions made with polyvinyl siloxane material with closed custom tray were dimensionally accurate than polyether impressions. On the contrary, the impressions made with polyether impression material and polyvinyl siloxane were dimensionally similar with both types of custom trays. Thus, this can be concluded that polyvinyl siloxane material with closed custom tray is the most reliable impression technique for implants.
Keywords: Implant impression, maxillary implants, dental implant, impression technique,