Abstract
ObjectiveMechanic strength, pore morphology and size are key factors for the three-dimensional (3D) printing of porous titanium scaffolds, therefore, developing optimal structure for the 3D printed titanium scaffold to fill bone defects in knee joints is instructive and important.MethodsStructural models of titanium scaffolds with fifteen different pore unit were designed with 3D printing computer software; five different scaffold shapes were designed: imitation diamond-60°, imitation diamond-90°, imitation diamond-120°, regular tetrahedron and regular hexahedron. Each structural shape was evaluated with three pore sizes (400, 600 and 800 μm), and fifteen types of cylindrical models (size: 20 mm; height: 20 mm). Autodesk Inventor software was used to determine the strength and safety of the models by simulating simple strength acting on the knee joints. We analyzed the data and found suitable models for the design of 3D printing of porous titanium scaffolds.ResultsFifteen different types of pore unit structural models were evaluated under positive pressure and lateral pressure; the compressive strength reduced when the pore size increased. Under torsional pressure, the strengths of the imitation diamond structure were similar when the pore size increased, and the strengths of the regular tetrahedron and regular hexahedron structures reduced when the pore size increased. In each case, the compressive strength of the regular hexahedron structure was highest, that of the regular tetrahedron was second highest, and that of the imitation diamond structure was relatively low. Fifteen types of cylindrical models under a set force were evaluated, and the sequence of comprehensive compressive strength, from strong to weak was: regular hexahedron > regular tetrahedron > imitation diamond-120° > imitation diamond-90° > imitation diamond-60°. The compressive strength of cylinder models was higher when the pore size was smaller.ConclusionThe pore size and pore morphology were important factors influencing the compressive strength. The strength of each structure reduced when the pore size (400, 600 and 800 μm) increased. The models of regular hexahedron, regular tetrahedron and imitation diamond-120°appeared to meet the conditions of large pore sizes and high compressive strength.
Highlights
Bone defects are common in the clinic and are usually associated with diseases, such as infection, osteolysis, original implant loosening or tumor excision
Through the analysis of the data in the table, the following conclusions can be drawn: (1) Under positive pressure, the maximum force of the imitation diamond and the regular hexahedron structure decreased with increasing pore size, the maximum force of the regular tetrahedron structure didn’t decrease with increasing pore size, and the maximum forces of the regular tetrahedron and the regular hexahedron structures were much larger than that of the imitation diamond structure, and the compressive strength of the regular hexahedron structure was the highest
(2) Under the lateral pressure, the maximum force of the five kinds of unit structures decreased with increasing pore size, and the maximum forces of the regular tetrahedron and regular hexahedron structures were much larger than that of the imitation diamond structure
Summary
Bone defects are common in the clinic and are usually associated with diseases, such as infection, osteolysis, original implant loosening or tumor excision. Bone loss has been addressed with methods such as cement, autogenous bone grafts, and artificial implants [1, 2]. Autogenous bone grafts are painful and source-limited, and are accompanied with. Bone cement can lead to complications of absorption poisoning, bone absorption poisoning, bone absorption and allergies [4]. Artificial implant materials, such as calcium phosphate [5], ceramic [6], polymer materials [7] and metal [8], have been developed. Metal is used in the clinic because of its high strength, high load capacity, shape memory, inertness and superelasticity.
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