Effect of Degradation on Long-term Stability of 3D-printed Dental Crowns

Abstract

3D printing technology in digital dentistry has led to innovative approaches for fabricating indirect dental restorations. However, a comprehensive assessment of the properties and long-term performance of these materials is essential. Therefore, this thesis aimed to evaluate the durability of mechanical, optical and surface properties of novel 3D-printed ceramic-filled resin composite materials indicated for definitive crown restorations. The first experimental chapter assessed the mechanical properties (flexural strength, flexural modulus, Martens hardness, indentation modulus and Vickers hardness) of three 3D-printed resin composites (Permanent Crown Resin, VarseoSmile Crown Plus, and Crowntec) and three milled resin composite blocks (BRILLIANT Crios, SHOFU Block HC and Grandio Blocs). The findings revealed that the 3D-printed definitive resin composites showed clinically acceptable mechanical properties, however, the milled resin composites showed significantly superior mechanical properties. The second experimental chapter explored the impact of immersion in food-simulating solvents on flexural strength, flexural modulus, Martens hardness, and indentation modulus of the same three 3D-printed resin composites and milled Grandio Blocs. Results indicated that exposure to solvents adversely affected the mechanical properties of all materials. Nevertheless, all tested materials showed acceptable mechanical properties after ageing. The third experimental chapter investigated the influence of artificial toothbrushing on surface roughness and gloss of the 3D-printed resin composites and the milled Grandio Blocs. Following 20,000 brushing cycles, both 3D-printed and milled resin composites exhibited increased surface roughness and reduced gloss, with 3D-printed materials exhibited comparatively lower wear resistance. Despite these changes, all tested materials maintained clinically acceptable gloss and roughness levels. The last experimental chapter examined the effects of immersion in various beverages on the colour stability (ΔE00), translucency, gloss and Martens hardness of the 3D-printed resin composites and milled Grandio Blocs. The results highlighted that both material type and beverage had a significant influence on the investigated properties, though ΔE00 of all materials remained within the clinically acceptable threshold of colour change across all beverages and measurement points.