Effect of Unit Cell Design and Volume Fraction of 3D-Printed Lattice Structures on Compressive Response and Orthopedics Screw Pullout Strength.

Abstract

We aimed to evaluate the effects of unit cell design and the volume fraction of 3D-printed lattice structures with relative densities of 30% or 45% on compressive response and orthopedics screw pullout strength. All 3D lattice models were created using FLatt Pack software (version 3.31.0.0). The unit cell size of sheet-based triply periodic minimal surfaces (TPMSs)-Gyroid and Schwarz Diamond-was 5.08 mm, whereas that of skeletal TPMS-Skeletal Gyroid, Skeletal Schwarz Diamond, and Skeletal Schoen I-Wrapped Package-was scaled down to 3.175 and 2.54 mm. Two photopolymer resin types-Rigid 10k and Standard Grey-were used. In uniaxial compression tests, Rigid 10k resin lattices failed at relatively lower strains (<0.11), while Standard Grey lattices endured higher strains (>0.60) and experienced less softening effects, resulting in stress-strain curve plateauing followed by lattice densification. ANOVA revealed significant effects of design and volume fraction at p < 0.001 on compressive modulus, screw pullout strength, and screw withdrawal stiffness of the 3D-printed lattice. The pullout load from 3D-printed lattices (61.00-2839.42 N) was higher than that from open-cell polyurethane foam (<50 N) and lower than that of human bone of similar volume fraction (1134-2293 N). These findings demonstrate that 3D-printed lattices can be tailored to approximate different bone densities, enabling more realistic orthopedic and dental training models.