3D-printed inorganic-filled resin under hydrothermal aging with different post-polymerization times: microstructure, optical, and mechanical properties

Abstract

Objective: This study aims to characterize and evaluate the optical and mechanical properties of a 3D-printed resin (NanoLab, Wilcos) at different post-polymerization times (0, 16, 32, and 60 minutes) before and after hydrothermal aging. Material and Methods: Characterization was performed via Scanning Electron Microscopy (SEM), energy spectroscopy (EDX), gravimetry to determine the chemical composition and inorganic filler content, and Fourier-transform Infrared Spectroscopy (FT-IR) to identify the degree of conversion of the resin (n=6). For mechanical and optical properties, flexural strength (n=8), microhardness (n=3), elastic modulus (n=3), color, and translucency (n=6) (CieLab2000) were measured. Results: Results showed that the microstructure reveals surface porosities. The organic matrix and inorganic filler contents of the resin were 46.75%, and 53.24%, respectively. Increasing post-polymerization time improved the degree of conversion and resulted in significant differences in mechanical properties and color stability (p < 0.001), whereas hydrothermal aging reduced hardness and elastic modulus but increased flexural strength. Conclusion: It was concluded that both the mechanical and optical behavior of the printed resin are significantly influenced by microstructure, chemical composition, post-polymerization times, and hydrothermal aging. A suggested suitable post-polymerization time is 32 minutes to ensure clinically acceptable color stability and achieve good mechanical properties, although this may impact the translucency of the material. The 3D- printed resin exhibited suitable properties for long-term dental restorations.

KEYWORDS

3D printing; Aging; Dental material; Dental resin; Flexural strength; Mechanical tests; Polymerization