Fracture resistance of nanocomposite 3D-printed resins designated for teeth fabrication: An in vitro analysis before and after thermal aging

<ns3:p>Background: this study was to evaluate the fracture resistance and elastic modulus of modified 3D-printed resins containing zirconium dioxide nanoparticles (ZNPs) and silicon dioxide nanoparticles (SNPs). Methods: Tooth-colored 3D-printed resin samples (ASIGA (AS)) and NextDent (ND)) were modified with silanized ZNPs and SNPs. Five groups (n=100) were prepared for each resin type, one without nanoparticles, and four groups (n=20 per group) with varying nanoparticles concentrations (0.5 wt. %ZNP, 1 wt.%ZNP, 0.5 wt.%SNP, and 1 wt.%SNP). Half of the specimens (110 samples) were subjected to thermal aging (TA; 5000 cycles). The fracture resistance and elastic modulus were evaluated, followed by Fourier-transform infrared and scanning electron microscopy analyses. An analysis of variance and Tukey’s post-hoc test were applied for data analysis. Results: Incorporating SNPs and ZNPs into the ND material significantly improved the fracture resistance compared to that of the control group, with 1 wt.%SNP showing the highest resistance (1405.9±128.4 MPa) and 0.5 wt.%ZNP the lowest (1047.5±100.6 MPa). However, the elastic modulus decreased notably with these additions, with the ND control group (3097.5±115.9 MPa) exhibiting the highest elastic modulus and ZNP groups (1772.0±128.8 MPa) exhibiting the lowest. In between NPs-reinforced groups per NPs type, there were no significant differences between SNPs groups (p=0.064) as well as ZNPs groups (p=0.072). For the AS material, similar enhancements in fracture resistance occurred; however, reductions in the elastic modulus were more significant in the ND material (p&lt;0.001*). For the AS material, SNP and ZNP addition improved fracture resistance relative to that of the control group. Post-TA, the elastic modulus significantly decreased in both the ND and AS materials (p &lt; 0.05). Compared to ND material, the increase in fracture resistance was less pronounced in the AS material. Conclusion: The addition of ZNPs and SNPs increased the fracture resistances of both materials. TA significantly reduced the fracture resistance and elastic modulus in most NP-incorporated groups. The ASIGA resin demonstrated superior performance and enhancements were more prominent which demonstrates promising characteristics for clinical use.</ns3:p>