3D evaluation of fit accuracy of different ceramic inlays using two digital measurement methods

Purpose Adaptation of inlays is crucial for clinical success. While various methods are currently available for measuring the marginal and internal fit of restorations, studies evaluating novel measurement techniques are scarce. This in vitro study aimed to evaluate two new digital methods and compare the marginal and internal fit of computer‐aided design and computer‐aided manufacturing (CAD‐CAM) inlays fabricated with three different materials by using the two methods. Materials and Methods A standardized inlay preparation was performed on a typodont right first molar and optically scanned. Three different material groups of inlays ( n = 15) were designed and fabricated based on the scanned preparations: (a) LD: lithium disilicate ceramic, (b) ZLS: zirconia reinforced lithium silicate ceramic, (c) RNC: resin nano‐ceramic. Digital silicone replica technique (DSRT) and triple‐scan technique (TST) were both used to measure the marginal gap (MG) at 250 ± points and the internal gap (IG) at 1300 ± points. Repeated measurement ANOVA was used to assess gap differences related to the materials. The reliability of measurement methods was tested by the coefficient of variation (CV), while paired t ‐tests and the Bland–Altman diagram were used to compare the differences in marginal fit values ( α = 0.05). Results The CV showed that the DSRT method had better repeatability. The MG and IG values measured by the DSRT were smaller than all samples except the IG of the RNC group. The RNC group demonstrated a significantly lower mean MG (27.47 ± 2.54 µm and 46.43 ± 5.79 µm, p < 0.05) than the other two groups with both methods. However, no statistically significant inter‐group differences were found in IG. Conclusion Both DSRT and TST are reliable for assessing the marginal and internal gap of inlays. TST is a new method for assessing the marginal and internal gap. As a reliable method widely used in marginal fit measurement, the reliability and stability of DSRT is better than TST, although their results are consistent. The marginal fit of CAD‐CAM inlays is influenced by the restorative materials, with RNC providing the best marginal fit.