In a dental clinical environment, various finish line locations of tooth preparations are often required for fixed dental prosthesis 33. Moreover, factors such as the difference in accuracy according to the type of scanner 29, 30, inaccuracy of the scan due to the patient’s saliva 31, and effect of ambient light in dental clinics on the accuracy 32 still require consensus. Since scan distortion occurs from the starting tooth of the intraoral scanning, the possible scan range for fixed dental prosthesis is still limited 28. However, the use of an intraoral scanner for fixed dental prosthesis still requires a solution from a clinical perspective 26, 27. The intraoral scanner has advantages of superior convenience, fast acquisition time of the virtual model, and superior accuracy (based on scanning for single unit) compared with the conventional method 22, 23, 24, 25. Previous studies can be different depending on what is designated as a reference model, such as the manufacturing precision of 3D printers 20 and the adjustment of the intaglio surface of the crown in the oral cavity 21. Previous studies have evaluated 3D trueness to verify the dimensional change of the intaglio surface of the fabricated dental prosthesis 17, 18, 19. In chairside dental CAD/CAM systems, CAM can be divided into milling and additive technologies, and three-dimensional (3D) printing (additive technology) is widely used in the fabrication of interim dental prostheses 14, 15, 16. The marginal fit of dental prosthesis considers the clinically acceptable range within 120 µm for reasons such as secondary caries, cement dissolution, and gingival inflammation 11, 12, 13. To verify the intraoral scanner, the scanning accuracy is also evaluated, but many previous studies have evaluated the marginal and internal fit of dental prosthesis fabricated using an intraoral scanner for application to dental clinics 7, 8, 9, 10. Therefore, the use of intraoral scanners for impression acquisition is increasing, and many studies have tried to verify scanning accuracy under various clinical conditions 4, 5, 6. The introduction of chairside dental computer-aided design and computer-aided manufacturing (CAD/CAM) systems in dental clinics is rapidly increasing 1, 2, 3. The use of an intraoral scanner should be decided on the clinical situation and needs. Crowns fabricated on the subgingival finish line caused inaccurate marginal fit due to poor fabrication reproducibility of the marginal region. Intaglio surface trueness was significantly different in the marginal region, with the highest value in the subgingival location ( P < 0.05). The marginal and internal fit showed significant differences according to locations ( P < 0.05) the marginal fit showed the best results in the supragingival finish line ( P < 0.05). One-way analysis of variance and Tukey HSD test were performed for comparisons (α = 0.05). Intaglio surface trueness was evaluated using a 3D inspection software. Marginal and internal fit were evaluated with a silicone replica technique.
Interim crowns were fabricated using a stereolithography three-dimensional (3D) printer (N = 16 per location). Crowns were designed based on the scanned area. The right maxillary first molar tooth preparation model was fabricated using a ceramic material and placed in four finish line locations (supragingival, equigingival, subgingival, and subgingival with a cord). This study evaluated the marginal and internal fit and intaglio surface trueness of interim crowns fabricated from tooth preparation scanned at four finish line locations.
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