Flexural properties and fatigue limit of 3D‐printed and milled resin‐based materials

Abstract Purpose The purpose of this study was to evaluate the flexural strength (FS), flexural modulus (FM), and fatigue limit (FL) of 3D‐printed resin‐based polymers and composites and compare them to 3D‐printed composites. Materials and Methods A bar‐shaped specimen (25 × 2 × 2 mm) was CAD designed according to ISO 4049:2019, and 60 duplicates of the 3D model were nested at a 45‐degree angle with the printing platform and 3D‐printed with three materials: denture teeth resin (Denture Teeth, Formlabs), temporary crown and bridge resin (Temporary CB, Formlabs), and composite (Flexcera Smile Ultra+, Desktop Health). The 3D model was also imported into a dental CAM software, duplicated 60 times, nested, and milled from a 3D‐milled composite puck (Ivotion Denture Teeth, Ivoclar). All specimens were post‐processed following the manufacturer's recommendation. The specimens were then subjected to a three‐point bending test until failure using a Universal Testing Machine at a crosshead speed of 0.75 mm/min, and FS and FM were calculated. The remaining thirty specimens were tested for Fatigue Limit using the staircase approach starting at 50% FS maximum up to 1.2 M cycles at 10 Hz. The data were analyzed using one‐way ANOVA and the Weibull distribution ( α = 0.05). Results The results showed that Ivotion and Flexcera had higher FS (110.3 ± 7.1 MPa and 107.6 ± 6.4 MPa, respectively) and FM (3.3 ± 0.1 GPa and 3.0 ± 0.2 GPa, respectively) compared to the 3D‐printed Denture Teeth (FS = 66.4 ± 18.5 MPa and FM = 1.8 ± 0.1 GPa) and Temporary CB (FS = 79.6 ± 12.1 MPa and FM = 2.7 ± 0.4 GPa). Weibull analysis showed that the Ivotion and Flexcera had a more uniform and narrower spatial distribution of defects ( m : 27.98 and 29.19) than the printed materials, which had m values of 8.17 and 4.11 for Temporary CB and Denture Teeth, respectively. Although no differences were found in the static properties (FS and FM) between Ivotion and Flexcera, Ivotion presented a higher endurance limit than Flexcera (51.43 vs. 40.95 MPa). The Temporary CB presented 21.08 MPa and Denture Teeth presented 17.80 MPa of endurance limit. Conclusions 3D‐milled (Ivotion Denture Teeth) and 3D‐printed (Flexcera Smile Ultra+) composites outperformed 3D‐printed resins (Formlabs Denture Teeth and Temporary Crown & Bridge) in terms of flexural properties and fatigue resistance. 3D‐milled (Ivotion) and 3D‐printed (Flexcera) composites exhibited similar flexural properties, but 3D‐milled composites showed a 25% higher fatigue endurance limit, suggesting improved clinical longevity.