Aim: The aim of this study was to evaluate the marginal integrity (vertical marginal gap) of monolithic zirconia crowns with two different finish lines and sintered with two different sintering protocols.
Materials and methods: Two metal dies with different finish line thicknesses (0.2 and 0.5 mm) were digitally designed and manufactured. Each metal die was scanned using an intraoral scanner (Primescan) and CEREC Software was used to design the crowns and give the milling order to the chairside milling machine (Primemill) to mill them. For each finish line, 16 zirconia crowns were obtained. Each group (n=16) was divided into two subgroups; conventional sintering using (Tegra speed furnace) and high-speed sintering using (CEREC SpeedFire furnace). Then, after sintering and polishing the crowns, the vertical marginal gap was measured using a stereomicroscope. The data obtained were collected, tabulated and subjected to statistical analysis.
Results: With regard to the vertical marginal gap, high-speed sintering exhibited statistically significant lower values (63.5 ± 19 um) than conventional sintering (67.3 ± 16.7 um) and there is no statistical significant difference between 0.5 and 0.2 mm finish line thicknesses.
Conclusions: 1. Monolithic zirconia crowns sintered using high-speed sintering protocol revealed lower marginal gaps than those sintered using conventional sintering protocol. While, there is no statistical significant difference between crowns with 0.2 and 0.5 mm finish line thicknesses.
2. High-speed sintering with more conservative preparation is a valid protocol for sintering zirconia crowns with more economical and time-saving attribute which complies with the chairside concept of digital dentistry.