Aim: To investigate the impact of finishing protocols and different immersion media on the fracture toughness and hardness of a recently introduced leucite-reinforced, glass-ceramic material.
Material and Methods: Fifty-four square-shaped zirconia specimens (10×10×1) mm were fabricated with a 1-mm layer of leucite-reinforced veneering material and adjusted using 40-μm diamond grinding stones to simulate occlusal adjustments. Specimens were randomly assigned to two groups based on their surface finish: polished and glazed. Specimens were further randomized into three subgroups based on the immersion solution: coffee, citric acid, and artificial saliva. Specimens were immersed in 5 mL of the solutions at 37°C for incubation, with coffee and artificial saliva groups immersed for 14 days and citric acid for 8-hours simulating two years of clinical use. Surface microhardness was evaluated using a Vickers microhardness tester, followed by fracture toughness evaluation through the indentation technique.
Results: Artificial saliva exhibited no significant difference in fracture toughness, but demonstrated significantly higher surface microhardness compared to the other immersion media. Regarding finishing protocol, no statistically significant difference in hardness or fracture toughness were observed for the leucite-reinforced veneering material.
Conclusion: The findings of this study suggest that immersion in acidic media, such as coffee and citric acid, can negatively impact the microhardness of zirconia veneered with leucite-reinforced ceramics. Since there were no statistically significant differences in fracture toughness between polished and glazed specimens, polishing can be considered a viable alternative to glazing for improving the surface finish of dental ceramics, potentially offering a more time- and cost-effective approach.