4D ‐Printed Biodegradable Mandibular Implant With Functionally Graded PLA / PEG and Tunable Infill Architecture for Minimally Invasive Reconstruction

ABSTRACT Minimally invasive mandibular reconstruction is constrained by the difficulty of inserting anatomically shaped implants through small surgical openings, motivating the development of deployable scaffolds capable of controlled deformation and in situ expansion. In this study, a 4D‐printed biodegradable mandibular implant was developed using a functionally graded PLA/PEG shell–core design that mimics the cortical–trabecular organization of native bone. A stiff PLA/PEG 95/5 outer shell provided load‐bearing capacity and geometric stability, while a compliant PLA/PEG 70/30 inner core enabled thermally triggered shape‐memory behavior near‐physiological temperature. Five trabecular infill architectures (hexagonal, gyroid, grid, lines, and triangular) were fabricated via dual‐material fused deposition modeling and evaluated under buccolingual compression, relevant to mandibular bending during mastication. The hexagonal infill achieved the highest compressive strength (1226.97 N), whereas the gyroid architecture exhibited the most favorable balance of strength, stiffness, progressive post‐yield deformation, and shape recovery (83.76%). Shape‐memory tests revealed architecture‐dependent recovery kinetics, with the gyroid showing rapid and uniform recovery (~120 s), while grid and triangular patterns exhibited reduced recovery fidelity. Optical microscopy confirmed that continuous filament connectivity promotes stable mechanical and 4D behavior. In vitro MTT assays demonstrated that all scaffold designs supported cell viability, with gyroid and hexagonal architectures showing the highest metabolic activity over 72 h. The results demonstrate that combining material grading with tunable infill architecture enables a mandibular implant that is load‐capable, safely deformable for minimally invasive insertion, and reliably expandable in situ.