Effects of silanized nano-Al2O3 fillers on the mechanical properties and printing accuracy of photopolymer resins for 3D printing dental applications

Abstract Three-dimensional (3D) printing dental applications are broadly applied in multiple specialties of dentistry facilitating diagnosis and treatment greatly. However, the current photopolymer materials for 3D printing dental applications often fail to yield the required quality due to their inferior mechanical properties. Thus, this study aims to explore the effects of silanized nano-Al2O3 fillers on the mechanical properties and printing accuracy of one of the most commonly used photopolymer resins, polyurethane acrylate (PUA). The modification of nano-Al2O3 particles by the silane coupling agent was characterized by Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric (TGA) analysis. Then, specimens were fabricated using PUA resins with 0 wt.% (control), 2 wt.%, 4 wt.%, and 6 wt.% silanized nano-Al2O3 fillers. The effects of silanized nano-Al2O3 fillers on the mechanical properties of the photopolymer resins were evaluated by Shore D hardness, tensile strength, and flexural strength tests. Moreover, the printing accuracy was assessed by the root-mean-square error (RMS) analysis. The results showed that the mechanical properties of the photopolymer resins were significantly improved when loaded with silanized nano-Al2O3 fillers. The highest values were observed in the resin with 4 wt.% filler content, improving hardness, tensile strength, and flexural strength by 11.7%, 31.1%, and 39.9%, respectively. For printing accuracy, loading 2 wt.% and 4 wt.% fillers did not influence the printing accuracy significantly. However, the incorporation of 6 wt.% fillers compromised the printing accuracy. Within the limits, this study has demonstrated that the incorporation of silanized nano-Al2O3 fillers can enhance the mechanical performance of photopolymer resins, indicating the potential of this material for improved quality of 3D printing dental applications.