The influence of implant placement depth and impression material on the stability of an open tray impression coping.

Statement of Problem: Subgingival positioning of a single dental implant may result in a less stable impression coping in a polymerized impression material.
Purpose: The purpose of this study was to evaluate the influence of a single dental implant placement depth and different impression materials on the stability of an open tray impression coping.
Material and Methods: Six polyvinyl chloride-based plastic models with single embedded internal hexagon implant analogs were fabricated. The implant analogs were placed equally with their surface 0, 1, 2, 3, 4, or 5 mm below the simulated gingival margin. Open tray impression copings were connected to the embedded implant analogs, and impressions were made with different vinyl polysiloxane (VPS) impression materials, polyethers, and an addition silicone-based occlusal registration material. The laboratory analogs were connected to the impression copings and the plastic trays were placed in a locking device. A measuring device, consisting of a compression force gauge connected to a platform moving at a speed of 3.2 mm/s, was fabricated. The impression trays were fixed so that the pole of the force gauge would touch the surface of the implant analog in the same place and push it 1.0 mm. Measurements of each specimen were made 5 times. Statistical analysis was performed with a 1-way ANOVA, the Tukey test, and the Pearson correlation coefficient (α=.05).
Results: There was a significant negative correlation between the dental implant placement depth and the force needed to move the impression coping (P<.05). In all depth groups, the impression coping was significantly more stable when the impressions were made with the occlusal registration material (P<.05).
Conclusions: As the dental implant placement depth increased, the force needed to move the impression coping decreased. The coping was significantly more stable when an occlusal registration material was used to make the impression.
(Copyright © 2012 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.)