Evaluation of the marginal fit of monolithic crowns fabricated by direct and indirect digitization

Abstract

Purpose: To evaluate the influence of intraoral and extraoral digitization systems on marginal discrepancy of monolithic lithium disilicate and monolithic zirconia computer-aided design-computer-aided manufacturing (CAD-CAM) crowns. Methods: Forty standardized machined stainless steel specimens with the characteristics of a first molar were manufactured and randomly assigned to two groups (n=20 each), depending on their material: monolithic lithium disilicate ceramic (LM), and monolithic zirconia (ZM). Then, each group was subdivided into two depending on the scanning system used: intraoral scanner (IOS), and extraoral scanner (EOS). The digitization process was standardized with two methacrylate devices, one for each scanner. After scanning and manufacturing of the crowns, the marginal discrepancy was measured under a scanning electron microscope (SEM). Data analysis was made using two-way analysis of variance (ANOVA) and the effect size with Cohen's d. Results: All the measurements were within the limits considered acceptable. Regardless the restorative material significant differences between scanners were observed, being the effect from low to moderate. However, no differences were observed between the scanners in either the lithium disilicate or zirconia group. Conclusions: The intraoral scan showed lower marginal discrepancy than the extraoral scan in CAD-CAM monolithic crowns, but these differences were not observed in each of the ceramic systems.