Optimized 3D printed zirconia-reinforced leucite with antibacterial coating for dental applications

Objectives: This study aims to produce by robocasting leucite/zirconia pieces with suitable mechanical and tribological performance, convenient aesthetics, and antibacterial properties to be used in dental crown replacement. Methods: Leucite pastes reinforced with 12.5%, 25%, and 37.5% wt. ZrO₂ nanoparticles were prepared and used to print samples that after sintering were characterized in terms of density, shrinkage, morphology, porosity, mechanical and tribological properties and translucency. A coating of silver diamine fluoride (SDF) and potassium iodide (KI) was applied over the most promising material. The material's antibacterial activity and cytotoxicity were assessed. Results: It was found that the increase of ZrO₂ reinforcement up to 25% enhanced both microhardness and fracture toughness of the sintered composite. However, for a superior content of ZrO₂, the increase of the porosity negatively affected the mechanical behaviour of the composite. Moreover, the composite with 25% ZrO₂ exhibited neglectable wear in chewing simulator tests and induced the lowest wear on the antagonist dental cusps. Although this composite exhibited lower translucency than human teeth, it was three times higher than the ZrO₂ glazed material. Coating this composite material with SDF+KI conferred antibacterial properties without inducing cytotoxicity. Significance: Robocasting of leucite reinforced with 25% ZrO₂ led to best results. The obtained material revealed superior optical properties and tribomechanical behaviour compared to glazed ZrO₂ (that is a common option in dental practice). Moreover, the application of SDF+KI coating impaired S. aureus proliferation, which anticipates its potential benefit for preventing pathogenic bacterial complications associated with prosthetic crown placement.