Page 444 - IJB-10-2

International Journal of Bioprinting 3D-printed silicon nitride-PEEK implants

Figure 3. Comparison in stiffness between PEEK and Si N -PEEK per solid, porous, and porous window designs: compression (A, B) and compression
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shear (C, D). Dotted line indicates the 5th percentile stiffness as per Peck et al. without shear in the beginning.
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percentile of ultimate compression strength defined by of ultimate shear strength defined by Peck et al. (4626 N)
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Peck et al. (14,728 N) (Table S3 in Supplementary File). (Table S3 in Supplementary File). Furthermore, solid and
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For compression shear tests, the cages were tested porous designs for both PEEK and Si N -PEEK materials
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above the 5th percentile ultimate shear force (1515 N). and porous window design of Si N -PEEK were tested
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The force–displacement curves were plotted for each above 75th percentile of ultimate shear strength defined by
sample. Data were normally distributed for all groups. Peck et al. (6868 N) (Table S3 in Supplementary File).
According to 2 × 3 factorial ANOVA, the main effect 3.2.2. Torsion
of material was significantly affecting the shear stiffness For torsion tests, the cages were tested until failure
(p < 0.001). Si N -PEEK cages had significantly higher according to ASTM F2077 (Figure 4).
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stiffness than PEEK cages (mean difference = 1185
N/mm, p < 0.001). The main effect of the design was The torque–angle curves were plotted for each sample.
observed within the borderline significance level (p = For each sample, ultimate moment, yield moment, and
0.049). The porous design’s shear stiffness was slightly stiffness values were calculated from the graphs (Table 1).
higher than the solid design’s stiffness (mean difference Torsional stiffness data were normally distributed for
= 950 N/mm, p = 0.04). Finally, the interaction between all the groups. According to 2 × 3 factorial ANOVA, both
the main effects (material and design) was not significant. main effects (material and design) significantly affected
In addition to the main effects, the group comparisons the torsional stiffness of cages (p = 0.001 and p < 0.001,
between PEEK and Si N -PEEK and the designs were respectively). Si N -PEEK cages had significantly higher
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analyzed (Figure 3). There was no significant difference torsional stiffness than PEEK cages (mean difference = 0.10
in shear stiffness between PEEK and Si N -PEEK per Nm/deg, p = 0.001). Cages with the solid design achieved
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design (Figure 3C). Similarly, the shear stiffness between the highest torsional stiffness and that was significantly
the designs for both PEEK and Si N -PEEK was not higher than the cages with the porous and porous window
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significantly different (Figure 3D). In addition to 5th design (mean difference = 0.13 and 0.14 Nm/deg, p = 0.004
percentile of ultimate shear strength loading, porous and p = 0.002, respectively). Finally, the interaction between
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window designs for PEEK were tested above 50th percentile the main effects (material and design) was not significant.
Volume 10 Issue 2 (2024) 436 doi: 10.36922/ijb.2124