Evaluation of the accuracy of direct digital impressions versus conventional silicone impressions for post-and-core with different root space diameters

Background: With the rapid advancement of digital impressions technologies, digital post-and-cores impressions can be applied in restorative dentistry. This study compared direct digital impressions with conventional silicone impressions to evaluate the influence of different post space diameters on the accuracy of digital post-and-core impressions at various depths. Methods: A total of three extracted teeth with different post space diameters were used to obtain three datasets s using an intraoral scanner (IOS) (TRIOS 5), with ten scans per group (1.5 mm, 2.0 mm, and 2.5 mm). An extraoral scanner (inEos X5) was used to scan the silicone impression ^{as the control. All files were exported as standard tessellation language (STL) files.the root mean square (RMS) deviations were analyzed between the experimental and control groups. Deviations were measured at standardized points across four regions at various depths (1.65 mm, 5.0 mm, 7.0 mm, and 9.0 mm). Results: In the evaluation of trueness, the mean RMS values at all post space diameters (1.5 mm, 2.0 mm, and 2.5 mm) and depths (1.65 mm, 5.0 mm, 7.0 mm, and 9.0 mm) were below 100 μm, indicating clinically acceptable accuracy (RMS < 100 μm). There were no significant differences in mean RMS values among the different diameters (1.5 mm, 2.0 mm, and 2.5 mm) (P > 0.05) At depths of 1.65 mm, 5.0 mm, 7.0 mm. The mean RMS values at 9.0 mm were significantly higher than those at 1.65 mm, 5.0 mm, and 7.0 mm (P < 0.05), indicating a marked decrease in scanning accuracy at this depth. Conclusions: For the post space diameter more than 1.5 mm and the depth is within 7 mm in single-rooted teeth, the direct intraoral scanning method using TRIOS 5 can be considered a reliable clinical option. For post space diameters of 2.0 mm and 2.5 mm, the scanning accuracy of the direct intraoral scanning method significantly decreases at a depth of 9 mm, but it can still be considered a viable option in clinical practice. A wider post space diameter (≥2 mm) can improve the intraoral scanning accuracy of deeper post spaces (≥7 mm).}