In vitro assessment of an intraoral scanner accuracy on abutments with horizontal preparation geometries and subgingival margins.

Objectives: This study evaluated the accuracy of the Medit i700 intraoral scanner (IOS) in capturing horizontal tooth preparations at different depths below the gingival margin and assessed its ability to detect surfaces beyond the finish line.

Methods: Using CAD software, two abutments of a standard maxillary first molar were designed with horizontal preparation and 0.8 mm chamfer at 1 mm and 2 mm depths below the gingival margin. The abutment designs, created in DentalCAD 3.0 Galway (Exocad), were 3D printed and mounted on a typodont with simulated pink gum. An experienced operator conducted 20 scans, with each scan taking between 1 and 2 min. The scanning process began at the occlusal surface of the right third molar and proceeded longitudinally to the contralateral molar, then extended buccally and palatally, resulting in two experimental groups: H-1 (1 mm depth) and H-2 (2 mm depth). Accuracy was assessed using Geomagic Control X software, with descriptive statistics and independent sample tests (α = 0.05) employed for group comparisons.

Results: No statistically significant difference was found in trueness between H-1 and H-2 (p=.053). However, precision differed significantly (p<.001). The IOS could not capture surfaces beyond the finish line in horizontal preparations.

Conclusions: Within study limitations, the horizontal preparation design hindered the IOS's ability to capture tooth anatomy beyond the finish line. Nonetheless, accuracy values at both 1 mm and 2 mm depths were clinically acceptable.

Clinical Significance,: The present study shows that the tested intraoral scanner is accurate enough to scan abutments with horizontal margins placed 1 and 2 mm below the gingiva.