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RESEARCH ARTICLE

Design Criteria for Patient-specific Mandibular Continuity

Defect Reconstructed Implant with Lightweight Structure

using Weighted Topology Optimization and Validated with

Biomechanical Fatigue Testing

Chun-Li Lin *, Yu-Tzu Wang , Chun-Ming Chang , Cheng-Hsien Wu , Wei-Heng Tsai 1
3
4
1
2
1 Department of Biomedical Engineering, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
2 Department of Mechanical and Electro-Mechanical Engineering, TamKang University, New Taipei City, Taiwan
3 National Applied Research Laboratories, Instrument Technology Research Center, Hsinchu, Taiwan
4 Department of Oral and Maxillofacial Surgery, Taipei Veterans General Hospital, School of Dentistry, National Yang Ming
Chiao Tung University, Hsinchu, Taiwan

Abstract: This study developed design criterion for patient-specific reconstructed implants with appearance consideration and
structural optimization of various mandibular continuity defects. The different mandible continuity defects include C (from left
to right canines), B (from 1 premolar to 3 molar), and A (from 3 molar to ramus) segments defined based on the mandible
rd
st
rd
image. The finite element (FE) analysis and weighted topology optimization methods were combined to design internal support
beam structures within different reconstructed implants with corresponding occlusal conditions. Five continuity mandibular
defects (single B/C/A+B and combination of B+C and B+C+B segments) were restored using additive manufacturing (AM)
reconstructed implant and bone plate to confirm reasonable design criterion through biomechanical fatigue testing. The worst
mandible strength was filtered based on the material mechanics and results from segmental bone length, thickness, and height
statistics from the established database containing mandible images of 105 patients. The weighted optimization analysis results
indicated that the sizes and positions of internal supporting beams within the reconstructed C, B, and A+B implants can be
defined parametrically through corresponding segmental bone length, width, and height. The FE analysis found that the weight
variation percentage between the parametric designed implants and original core solid implants in the C, B, and A+B was reduced
by 54.3%, 63.7%, and 69.7%, respectively. The maximum stress values of the reconstructed implant and the remaining bone were
not obviously reduced but the stress values were far lower than the material ultimate strength. The biomechanical fatigue testing
indicated that all cases using the AM reconstructed implant could pass the 250,000 dynamic load. However, condyle head, bone
plate fracture, and bone screw loosening could be found in cases using bone plates. This study developed a design criterion for
patient-specific reconstructed implants for various mandibular continuity defects applicable for AM to further clinical use.

Keywords: Patient-specific implant; Mandibular continuity defect; Topology optimization; Finite element analysis; Additive
manufacturing; Biomechanical testing
*Correspondence to: Chun-Li Lin, National Yang Ming Chiao Tung University, Hsinchu, Taiwan; cllin2@nycu.edu.tw

Received: August 23, 2021; Accepted: October 18, 2021; Published Online: December 10, 2021
Citation: Lin CL, Wang YT, Chang CM, et al., 2022, Design Criteria for Patient-Specific Mandibular Continuity Defect Reconstructed
Implant with Lightweight Structure Using Weighted Topology Optimization and Validated with Biomechanical Fatigue Testing. Int J Bioprint,
8(1):437. http:// doi.org/10.18063/ijb.v8i1.437

1. Introduction design (CAD) technologies to reconstruct patient-
specific mandibular continuity defects are accepted to
The application integrating metal additive manufacturing restore the patient appearance and mandible structural
(AM), medical image processing, and computer-aided strength [1-11] . The subsequent combination of chemical

© 2021 Author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution License, permitting distribution and
reproduction in any medium, provided the original work is properly cited.
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