Analyzing the Physical Attributes of Additively Manufactured Zirconia Crowns

Objectives: CAD/CAM systems are increasingly used in dentistry due to efficiency and reduced material use. They create virtual models for dental prosthesis design through 3D printing or milling, offering advantages like time efficiency but facing limitations in handling complex structures and generating waste.
In dental CAD/CAM, including various methods like DLP and SLA, 3D printing is prominent for applications like metal denture frameworks. However, 3D printing of ceramic restorations is less common.
This study aims to evaluate ZrO2 crowns' physical properties based on manufacturing methods. It hypothesizes that different 3D printing methods won't significantly affect properties like accuracy, microstructure, bond strength, and hardness, and 3D printed zirconia specimens will yield results like milled ones.
Methods: This study comprised six groups, each with ten crowns, totaling 60 crowns. The groups were divided based on manufacturing methods, including milling and various 3D printing techniques. The crowns were evaluated for factors replica, SEM, shear bond test, vickers micro hardness test.
Results: The DLP VAT group had the largest margin in the replica's margin area, followed by DLP spreading, DLP gradation, and DLP circular spreading groups, which were equal to or larger than SLA spreading and milling groups (p < 0.001, p < 0.001). SEM images showed agglomerated zirconia particles and the formation of cracks after sandblasting in all groups. Significant differences in shear bond strength were observed, with the DLP spreading group having the highest, followed by DLP circular spreading and DLP spreading gradation groups, which were better than milling and DLP VAT. SLA spreading had the lowest shear bond strength. Vickers hardness measurements showed no significant differences between groups (p = 0.95). The highest hardness was in group DLP spreading gradation(8.97(5.73)), and the lowest was in DLP spreading(6.97(3.47)).
Conclusions: This study assessed ZrO2 crown manufacturing methods, finding variations in properties, such as margin size and shear bond strength, with implications for clinical use in dentistry.