The Effect of Implant Connection Length on the Dimensional Impression Accuracy of Inclined Implants

Purpose: Accurate recording of implant locations is essential for precise passively fitting prostheses with proper support. This in vitro study evaluated the accuracy of impressions made of parallel and nonparallel implants with different lengths of impression coping connections. Materials and Methods: A reference model containing four internal-connection implant analogs (two at 0 degrees and two at 30 degrees in relation to the perpendicular line) was fabricated. Thirty medium-consistency silicon impressions of this model were made using the open-tray impression technique. Three groups of 10 specimens each were made with different impression coping connection lengths (2, 1.5, or 1 mm). Impressions were poured with type IV stone. The positional accuracy of the implant replica heads in the x-, y-, and z-axes was evaluated using a coordinate measuring machine, and measurements were compared with the obtained dimensions from the reference model. Data were analyzed with two-way analysis of variance (α = .05). Results: There was no significant difference in impression accuracy, regardless of the lengths of the impression connections. Additionally, there was no significant difference between the impression accuracy of inclined and straight implants, except in the y-axis (P = .006). Conclusions: Within the limitations of this study, the accuracy of implant impressions did not differ for different lengths of transfer coping connections of inclined and straight implants.