Modifying Digital Occlusal Spacer Effect on the Marginal Gap of Zirconia-Reinforced Lithium Silicate Crowns: In Vitro Scanning Electron Microscopy Evaluation.

The article investigates the impact of modifying digital occlusal spacers on the marginal gap of full monolithic zirconia-reinforced lithium silicate (ZLS) crowns fabricated using a 4-axis milling machine. In an in vitro study with 45 acrylic maxillary first molar abutments, three groups with occlusal spacers of 60, 90, and 120 μm were compared using scanning electron microscopy (SEM) to measure marginal gaps after cementation. Results showed that all groups achieved clinically acceptable marginal gaps (<120 μm), but the 120 μm spacer group had a significantly larger marginal gap than the 60 and 90 μm groups, with no significant difference between the latter two. The study concludes that a 60 μm digital occlusal spacer is most favorable for ZLS crowns like Celtra Duo, and recommends further research on digital occlusal spacer settings across different materials and technologies.