Purpose: To evaluate the accuracy of intraoral scanners by comparing the marginal fit of 70 all-ceramic crowns fabricated from both conventional impressions and intraoral scans. Materials and Methods: A total of 70 posterior teeth requiring single-crown restorations randomly underwent either intraoral scanning or conventional impression-taking, followed by laboratory scanning of the casts in a parallel-group randomized controlled trial (RCT). Subsequently, 70 monolithic all-ceramic crowns were CAD/CAM fabricated; only the impression technique differed. The marginal fit, internal fit, adjustment time required for insertion and occlusal contacts, and visual analog scale (VAS) scores assessing dentists’ satisfaction with the crowns were clinically evaluated by a calibrated examiner who was blinded to the groups. Data were analyzed using independent samples t test and likelihood-ratio test or Fisher exact test. All tests were performed with α = .05. Results: The mean marginal fit with intraoral scanning (57.94 ± 22.51 μm) was better than with diagnostic cast scanning (82.98 ± 21.72 μm). The difference was statistically significant (P = .000). The differences in internal fit, adjustment time for crown insertion and occlusal contacts, and VAS scores were also significant, and the secondary outcomes were in favor of intraoral scanning. Conclusions: Within the limitations of this clinical trial, CAD/CAM–fabricated single-tooth restorations in the posterior region produced with an intraoral scanning technique using TRIOS were found to be a more accurate, efficient alternative to restorations based on conventional impressions in combination with the laboratory scanning technique.