Influence of the Processing Method on the Nano-Mechanical Properties and Porosity of Dental Acrylic Resins Fabricated by Heat-Curing, 3D Printing and Milling Techniques.

: Acrylic resin-based materials are a versatile category used extensively in various dental applications. Processed by current modern technologies, such as CAD/CAM technologies or 3D printing, these materials have revolutionized the field of dentistry for the efficient creation of dental devices. However, despite their extensive use, a limited number of comparative studies exist that investigate how different processing methods-such as traditional techniques, 3D printing, and CAD/CAM milling-impact the nano-mechanical behavior and internal porosity of these materials, which are critical for their long-term clinical performance. The purpose of this study is to evaluate the nanomechanical properties (hardness, elasticity, and stiffness) and micro-porosity of acrylic resin-based materials indicated for temporary prosthodontic appliances manufactured by new technologies (milling, 3D printing) compared to traditional methods. The hardness, elasticity, and stiffness measurements were performed by the nano-metric indentation method (nanoindentation), and the quantitative morphological characterization of the porosity of the acrylic resin samples obtained by 3D printing and CAD/CAM milling was performed by micro-computed tomography. According to nanomechanical investigations, CAD/CAM milling restorative specimens exhibited the greatest mechanical performances (E5.233 GPa and H0.315 GPa), followed by 3D printed samples, while the lowest mechanical properties were registered for the specimen fabricated by the traditional method (E3.552 GPa, H0.142 GPa). At the same time, the results of porosity studies (micro-CT) suggested that 3D printed specimens demonstrated a superior degree of porosity (temporary crown-22.93% and splints-8.94%) compared to CAD/CAM milling restorative samples (5.73%). The comparative analysis of these results allows for the optimal selection of the processing method in order to ensure the specific requirements of the various clinical applications.