Effect of using scan body accessories and inter-implant distances on the accuracy of complete arch implant digital impressions: An in vitro study.

Purpose: To introduce a novel design for scan body accessory parts that are reusable, easy to attach and detach without permanent change of the scan body, and can be used with different inter-implant distances to enhance the accuracy of complete arch implant scans.

Materials And Methods: A maxillary polymethylmethacrylate (PMMA) model with a soft tissue replica was fabricated with four implant analogs located at tooth positions 17, 13, 22, and 27 with 18, 25, and 30 mm inter-implant distances. Four scan bodies (SBs) were attached to the implants. The model was scanned with a laboratory scanner to be used as a reference scan. A total of 40 scans were made with the same intraoral scanner and they were divided equally into two groups. Group A: Complete arch implant scans without scan body accessories (n = 20), and Group B: Complete arch implant scans with scan body accessories (n = 20). Intraoral scans were exported and superimposed on the reference scan using reverse engineering inspection software to be evaluated for 3D deviations, angular deviations, and linear deviations. Statistical analysis was performed with student t-test and analysis of variance (ANOVA) with repeated measures followed by post hoc adjusted Bonferroni test. The level of significance was set at P = 0.05.

Results: The scan body accessories decreased both the 3D and linear deviations, with a statistically significant difference at SB4 for the 3D deviation (P = 0.043) and the linear inter-implant discrepancies between SB1-SB2 and SB3-SB4 (P = 0.029 and < 0.001), respectively. However, there was no statistically significant difference in angular deviation between the study groups. Implant positions had significant differences within each group.

Conclusions:  A significant improvement in the accuracy of the complete arch implant digital impression was achieved by using the scan body accessories, particularly in reducing the 3D and linear deviations at the most distant implant positions.