Mechanobiological Approach to Design and Optimize Bone Tissue Scaffolds 3D Printed with Fused Deposition Modeling: A Feasibility Study

Abstract

In spite of the rather large use of the fused deposition modeling (FDM) technique for the fabrication of scaffolds, no studies are reported in the literature that optimize the geometry of such scaffold types based on mechanobiological criteria. We implemented a mechanobiology-based optimization algorithm to determine the optimal distance between the strands in cylindrical scaffolds subjected to compression. The optimized scaffolds were then 3D printed with the FDM technique and successively measured. We found that the difference between the optimized distances and the average measured ones never exceeded 8.27% of the optimized distance. However, we found that large fabrication errors are made on the filament diameter when the filament diameter to be realized differs significantly with respect to the diameter of the nozzle utilized for the extrusion. This feasibility study demonstrated that the FDM technique is suitable to build accurate scaffold samples only in the cases where the strand diameter is close to the nozzle diameter. Conversely, when a large difference exists, large fabrication errors can be committed on the diameter of the filaments. In general, the scaffolds realized with the FDM technique were predicted to stimulate the formation of amounts of bone smaller than those that can be obtained with other regular beam-based scaffolds.

An Algorithm to Optimize the Micro-Geometrical Dimensions of Scaffolds with Spherical Pores

“…The experimental tests previously conducted with FDM demonstrated that this technique is suitable to build accurate scaffold samples only in the cases where the strand diameter is close to the nozzle diameter. Conversely, when a large difference exists, large fabrication errors can be committed on the diameter of the filaments [ 17 ]. Scaffolds fabricated with selective laser sintering (SLS) show dimensional deviations—with respect to the nominal dimensions—up to 7.5% [ 28 ].…”

“…The model includes also the granulation tissue, highlighted in red ( Figure 5 ), occupying the scaffold pores. Both the scaffold and the granulation tissue were modeled as biphasic poroelastic materials with the same material properties ( Table 1 ) as those utilized in previous studies [ 15 , 17 , 18 ].…”

Bioengineering Bone Tissue with 3D Printed Scaffolds in the Presence of Oligostilbenes

“…The bed and nozzle temperature parameters are not inside the interval suggested by the 3D printer supplier, but since manufacturing time is lower than 5 min, the machine is able to complete the workpiece without damages. The different pore sizes were obtained setting on the Cura slicing software the distance between lines equal, respectively, to 0.75 mm for small pores, 0.9 mm for medium pores and 1.15 mm for large pores [ 29 ]. Figure 1 shows the Ultimaker 3D printer and samples of the manufactured scaffolds.…”

Challenges on optimization of 3D-printed bone scaffolds

“…For example, it has been reported that the FDM printing technique can accurately build scaffolds when the diameter of strands used to make PLA scaffolds were close to the nozzle diameter. On the contrary, in case of a large difference, fabrication errors were large and imposed on the filament diameter due to inappropriate material flow [272]. The strand diameters tested for nozzle diameter of 800 µm were 500, 600, 700, and 800 µm, and for nozzle diameter of 400 µm it was 400 µm.…”