Effect of intraoral scanning distance on the marginal discrepancy of milled interim crowns.

Purpose: To compare the marginal discrepancy between milled interim crowns fabricated using intraoral digital scans acquired at different scanning distances.

Materials And Methods: Ten acrylic typodont teeth were prepared for interim crowns. Three different resin frames of 2.5-, 5-, and 7.5-mm heights were fabricated and attached to an intraoral scanner (Omnicam). Three groups were created based on the different scanning distances tested: 2.5 mm (Group A), 5 mm (Group B), and 7.5 mm (Group C). Intraoral digital scans were performed on four tooth surfaces: mesial, distal, buccal, and lingual (n = 10). Each experimental scan was used to design and fabricate a milled polymethylmethacrylate anatomically contoured crown. Vinyl polyether silicone was used three times to assess the marginal discrepancy of the specimens by measuring five marginal points on digital photographs. One-way analysis of variance test was used to analyze the data, followed by Tukey's honestly significant difference test (α = 0.05).

Results: The mean marginal discrepancy values in Group C were significantly higher than those in Groups A (p ≤ 0.000) and B (p = 0.001). There was no significant difference between Groups A and B (p = 0.702). There were no significant differences among the four surfaces in any of the scanning distance groups (p  = 0.583, p  = 0.390, and p  = 0.135; p > 0.05).

Conclusions: The interim crowns fabricated with a scanning distance of 7.5 mm showed the greatest marginal discrepancy when compared with crowns fabricated using 2.5- and 5-mm scanning distances.