The fit of crowns produced using digital impression systems

Compare the marginal and internal fit of crowns manufactured using four different digital impression systems with crowns manufactured using conventional impression technique, that served as a control group. Fifty all-ceramic crowns were fabricated using 50 standardized dies divided into five groups, each group representing one impression system. Each crown was cemented onto its respective model and sectioned into four segments. The marginal and internal fit were measured at 8 predefined points. A total of 1567 measurements were made, statistically analyzed and compared with crowns fabricated using the five systems. The following was found: (1) No significant difference was found with regard to marginal gap when comparing the control group to any of the digital systems. (2) Lava (TM) had smaller marginal gaps than CEREC (R) and iTero (R), (3) CEREC and Lava had smaller gaps in the chamfer compared to iTero and the control, (4) E4D (R) showed smaller gaps than CEREC at measuring points 4-8 and CEREC a smaller gap at point 2, (5) Lava showed smaller gaps than CEREC at measuring points 1,3 and 5-8. (6) Lava had smaller gaps than iTero at measuring points 1-4,7 and 8. All differences presented were significant. In conclusions, crowns manufactured using digital impressions present a marginal and internal fit equal to, or better than, crowns made using a conventional impression method. The marginal and internal fit of reconstructions made using digital impression techniques could improve with a lower initial setting of the spacer.