Comparison of the accuracy of conventional and digital impression techniques in complete-arch implant restoration

The aim of this study was to evaluate the accuracy of conventional and digital impressions of implants placed at different distances, parallel and angled. On edentulous upper jaw model, for regions 11, 13, 14, 15, 22, 24 and 26, respectively; a total of 7 implant analogues and multi-units with 0, 0, 15, 30, 0, 15, 30 angulations abutments were placed. Later, working model with scanbodies placed on multi-unit abutments scanned with Eos X5i laboratory scanner (inEos X5; Dentsply Sirona Dental, Benshein, Germany). Conventional impression group (KG) was created with an individual impression tray and an open tray impression technique on impression posts splinted with pattern resin. In the digital impression group, a total of 3 different intraoral scanners, Primescan (PS), Trios 4 (T) and Medit i500 (MI), were used (4 impression groups and n:10). The deviation values were calculated by superimposing the 3D models of 3 different intraoral scanners and conventional impressions with the reference model in the Geomagic Control X program. Obtained data were analyzed with IBM SPSS Statistics 22. Normal distribution was evaluated with Kolmogorov-Smirnov and Shapiro Wilks tests. Kruskal Wallis test was used to compare the parameters between groups and Dunn's test was used to determine the group that caused the difference. According to the results obtained, a statistically significant difference was found between the conventional impression and digital impression groups in terms of impression trueness (p<0.05). The trueness value of PS impression group (0.110 µm) was higher than the trueness value of KG (0.153 µm). However, there was no statistically significant difference between CG and PS and MI groups. PS group had significantly higher trueness than MI and T measurement groups. The T group is the group with the highest deviation value (0.283 µm) in terms of measurement accuracy, followed by the MI group (0.213 µm). There was no significant difference between the PS (0.163 µm), MI (0.241) and T (0.313) impression groups in terms of precision of the impressions. There was a significant difference between KG (0.052) and the other 3 groups, and KG showed the lowest deviation value in terms of precission. When the accuracy compared among the groups, for complete-arch implant applications, since the PS and MI groups showed similar accuracy with the conventional impression, digital impression can be used as an alternative to conventional impression. When the precission of the impressions examined, the scanning parameters should be applied carefully, since intraoral scanners showed significantly higher deviation values compared to the conventional impression. Keywords: Digital Impression, Implant Supported Restorations, Impression Precision, Impression Trueness, Intraoral Scanners