Page 345 - IJB-10-3

International Journal of Bioprinting Acoustic analysis of 3D-printed ossicles

4.4. Frequency response analysis of HxH of the normal ear in the 0.75–2.00 kHz frequency range.
Figure 13 shows the stapes floor displacement of three The other combinations all have significantly reduced
material combinations: HA/PCL-TC4-HA/PCL (HTH), hearing levels.
HA/PCL-316L-HA/PCL (H3H), and HA/PCL-HA/
PCL-HA/PCL (HHH). In these three combinations, the 5. Conclusion
malleus and stapes are fixed as HA/PCL, and the incus
material is replaced. The density of the malleus bone is Titanium alloy TC4, stainless steel 316L, and composite HA/
altered from the normal values of 2.55 g/cm , 4.53 g/cm , PCL were chosen as materials for ossicular replacement.
3
3
and 3.7 g/cm to 1.58 g/cm , and the mass decreases to Using finite element analysis and an in vitro verification
3
3
0.61, 0.34, and 0.42 times the normal values, respectively. experiment, individual replacements of the ossicles and
Additionally, the elastic modulus changes from 14.1 GPa three bone material replacements were conducted for
to 787.2 MPa, which is reduced to 1/17.9 times that of a frequency response analysis. In the individual ossicle
normal human ear. replacements, both TC4 and 316L effectively replaced the
Figure 14 shows the ESP level changes in HTH, H3H, malleus and incus, with a significant increase in average
and HHH. It can be clearly seen that when both the malleus displacement of the stapes, achieving a match in auditory
and stapes are HA/PCL, the three curves mostly lie below behavior. However, when replacing the malleus and incus
the threshold line. In the frequency range of 0.25–0.5kHz, with HA/PCL, there was a slight decrease in hearing in the
the hearing response values of HTH vary from -10.9 dB low-frequency range. On the other hand, when replacing the
to 2.5 dB as the frequency increases. The HHH curve also stapes with the three mentioned materials, varying degrees
shows an upward trend, precisely recovering to the normal of worsening were observed. When all three ossicles were
hearing level at 1 kHz. The H3H curve exhibits an initial replaced simultaneously and the finite element simulation
rise followed by a plateau, with no feedback in the low- results were compared with laser vibrometer data, it was
frequency range, and the minimum worsening value is found that among the three ossicles, with the same incus
1.84 dB. and stapes materials, the malleus performed better with
Among the nine different combinations of ossicular TC4, followed by 316L. With the same malleus and stapes
chain materials mentioned above, TTH shows an improved materials, the incus made of TC4 still performed better
hearing gain in the mid-high frequency range, with an than 316L and HA/PCL. With the same malleus and incus
overall hearing change of within 3 dB. T3H and 3TH materials, the stapes made of HA/PCL performed better
exhibit an overall hearing change of ±5 dB. HTH, H3H, than TC4 and 316L. Furthermore, the combination of
and HHH demonstrate hearing behavior within ±2.5 dB TTH was found to bear a higher resemblance to a real

Figure 13. Stapes floor displacement of HTH, H3H, and HHH.

Volume 10 Issue 3 (2024) 337 doi: 10.36922/ijb.2040