Date Published: March 14, 2019
Publisher: Springer International Publishing
Author(s): Jiajie Hu, Joanne H. Wang, Russel Wang, Xiong Bill Yu, Yunfeng Liu, Dale A. Baur.
Our long-term goal is to design and manufacture a customized graft with porous scaffold structure for repairing large mandibular defects using topological optimization and 3D printing technology. The purpose of this study is to characterize the mechanical behavior of 3D printed anisotropic scaffolds as bone analogs by fused deposition modeling (FDM).
Cone beam computed tomography (CBCT) images were used to reconstruct a 3D mandible and finite element models. A virtual sectioned-block of the mandible was used as the control group and the trabecular portion of the block was modified by topological optimization methods as experimental groups. FDM (FDM) printed samples at 0, 45 and 90 degrees with Poly-lactic acid (PLA) material under a three-point bending test. Finite element analysis was also used to validate the data obtained from the physical model tests.
The ultimate load, yield load, failure deflection, yield deflection, stress, strain distribution, and porosity of scaffold structures were compared. The results show that the topological optimized graft had the best mechanical properties.
The results from mechanical tests on physical models and numerical simulations from this study show a great potential for topological optimization and 3D printing technology to be served in design and rapidly manufacturing of artificial porous grafts.
Autograft and allograft are commonly used for bone grafting procedures to repair segmental bony defects, which usually result from trauma, infection and tumor resection of tumors [1–3]. The limitations of autografts are donor site morbidity , lack of bone volume for a large defect [5, 6], and possible nerve damage. While allografts are limited by anatomical variations, genetic differences, and possible disease transmission [7, 8]. It is important to restore a critical-sized mandibular defect to its original size and shape to achieve desirable facial esthetics and functional outcome for subsequent prosthetic reconstruction. Microvascular free fibular graft is a common method for mandibular reconstructions to repair a large segmental defect [9–12]. It is impossible of using a fibular bone to match the shape and size of the resected portion of a mandible. Therefore, there are many prosthetic complications for those patients who received surgical and prosthetic reconstruction of the mandible . One promising approach for obviating the aforementioned complication is the implementation of 3D printing strategies for the manufacturing of customized artificial bio-graft [14, 15].
PLA has not been currently used as bone analogs for mandibular reconstruction surgery in load-bearing areas. Its excellent biocompatibility and biodegradation properties are important reason for extensively studied in the literature as a scaffolding material for tissue engineering in craniofacial areas. Further strategies to improve its mechanical properties based on PLA modifications and PLA nanocomposite designs may be the key to improve its mechanical properties for mandibular reconstruction. This project is to provide valid information for readers to understand mechanical issues of 3D printed biomaterials.
A new method of restoring segmental bony defects of the mandible to its exact original shape, size and form is proposed by using 3D printing technology and topological optimization method. 3D printing technology can easily fabricate complex shapes to match patients’ unique defects. The 3D printed graft samples had anisotropic properties. Printing direction and internal design of the grafts significantly affected their mechanical properties. The grafts printed at 0° with topology optimization had the best results. Although the results of this study are based on PLA material, the proposed methodologies are also applicable to other promising 3D printing materials such as Polyetheretherketone (PEEK). 3D printing technology and topological optimization are useful tools in fabrication and designing bone analogs for mandibular reconstruction.