Superiority of Triply Periodic Minimal Surface Gyroid Structure to Strut-Based Grid Structure in Both Strength and Bone Regeneration

The aging population has rapidlydriven the demand forbone regeneration.The pore structure of a scaffold is a critical factor that affectsits mechanical strength and bone regeneration. Triply periodic minimalsurface gyroid structures similar to the trabecular bone structureare considered superior to strut-based lattice structures (e.g., grids)in terms of bone regeneration. However, at this stage, this is onlya hypothesis and is not supported by evidence. In this study, weexperimentally validated this hypothesis by comparing gyroid and gridscaffolds composed of carbonate apatite. The gyroid scaffolds possessedcompressive strength approximately 1.6-fold higher than that of thegrid scaffolds because the gyroid structure prevented stress concentration,whereas the grid structure could not. The porosity of gyroid scaffoldswas higher than that of the grid scaffolds; however, porosity andcompressive strength generally have a trade-off relationship. Moreover,the gyroid scaffolds formed more than twice the amount of bone asgrid scaffolds in a critical-sized bone defect in rabbit femur condyles.This favorable bone regeneration using gyroid scaffolds was attributedto the high permeability (i.e., larger volume of macropores or porosity)and curvature profile of the gyroid structure. Thus, this study validatedthe conventional hypothesis using in vivo experiments and revealedfactors that led to this hypothetical outcome. The findings of thisstudy are expected to contribute to the development of scaffolds thatcan achieve early bone regeneration without sacrificing the mechanicalstrength.