Page 190 - IJB-9-4

International Journal of Bioprinting 3D-printed middle ear prostheses

this issue combined with frequency-dependent vibration commercial multi-slice CT (MSCT) was used, while the
modes [40-42] of the stapes has been solved using 3D LDV study by Kamrava et al. also used a micro-CT device.
[34]
setup to measure velocity of the stapes posterior crus. In a According to the study by Hirsch et al. , the most
[17]
study by Hato et al. , an increased piston-like motion of important structures in prosthesis design were seen in
[41]
the stapes was found at all frequencies when the cochlea dissected temporal bones with adequate resolution but
was drained. In this study, velocity of the medial side of the in in vivo use, the resolution could be weaker, and thus,
stapes footplate was chosen to be measured using single- designing individualized ME prostheses with commercial
axis LDV setup with a mirroring glitter placed in the MSCT could be hard. Micro-CT, on the other hand, cannot
middle of the footplate to find movement of the stapes that be utilized in clinical use because of its high radiation
was as piston-like as possible and to allow direction of the exposure, and therefore, imaging of ossicles with adequate
laser beam to be as repeatable as possible when changing effective doses for 3D printing is currently challenging due
between different ME transduction modes. to relatively low resolution. In the future, cone-beam CT
[43]
Titanium is a well-known material used in in vivo may become more common in ME imaging and it could
prostheses and compatible with bone tissue. Light and also be considered for use in individualized prosthesis
thin structures, such as the shaft of a ME prosthesis, can designing.
also be made of titanium. The costs of titanium prostheses In the current study, four different temporal bones
are higher, which can affect user-friendliness . The 3D were used. Prostheses used in these bones were selected so
[22]
printer and polymer material used in this study could that they fit precisely in the individual MEs. The current
not be used to create structures as thin as those seen in experimental setting enables individual anatomical ME
the current commercial titanium prostheses. Other 3D circumstances to be taken into account. 3D printing
[32]
printing processes with biocompatible materials that are offers the advantage to print prostheses in different sizes,
already accepted for in vivo use could be utilized in ME and this can be availed both in surgical training and in
prosthesis production. On the other hand, 3D printing developmental work when planning novel prosthesis
in bone tissue engineering could be also a promising design. As a consequence, 3D printing can offer a budget-
[33]
alternative solution in the future. friendly way in future individualized ME prosthesis
The 3D-printed liquid photopolymer used in this study production.
to 3D-print prostheses is not accepted as in vivo prosthesis In the future, more studies are needed focusing on
material and is thus not suitable for clinical use. However, novel prosthesis designs and additive manufacturing
the 3D-printed liquid photopolymer prostheses seem to be technologies of 3D printing, especially to produce thin
valuable practice tools for otosurgery training due to their structures and to test their acoustical performance.
good microsurgical usability and low production costs, as Extensive material testing will also be needed if clinical
one 3D-printed PORP costs less than 5 USD. In this study, applications will be pursued.
only one PORP design was used, but with 3D modeling
and printing, it will be easy and cheap to fabricate different
types of PORPs and TORPs for surgical training. 5. Conclusion
Based on our experience, most of the flaws of the first- This study shows that acoustical performance and surgical
generation PORPs were related to the 3D printing process maneuverability of a 3D-printed photopolymer PORP
itself. The laser spot size and the XY resolution of the 3D compares well with that of a commercial titanium PORP.
printer are the limitations to making small features. In Currently, these 3D-printed photopolymer PORPs may
addition, the beam is typically Gaussian distributed, and well be used in otosurgical training, but before possible
there are always reflections. One of the biggest challenges clinical applications, several technical issues must be
for these flaws is that in inverted vat photopolymerization, solved. Biocompatibility issues and utilization of printing
there are peel forces that affect the print as it separates from materials already accepted for patient use must be
the surface of the tank. This makes printing of miniature explored. More studies are warranted concerning different
features challenging since they typically deform or break. additive manufacturing processes and their accuracy in
By widening the shaft diameter in the second-generation printing microscopic objects, printing materials, novel
PORPs, we were able to find construction that could be prosthesis designs, and acoustical performances of the
3D-printed more reliably. novel prostheses. In the future, with more precise imaging
modalities available for patient use, individualized ossicular
In studies by Hirsch et al. and Kamrava et al. , chain replacement prostheses could be feasible using
[34]
[17]
different types of PORPs were designed using CT imaging additive manufacturing techniques with biocompatible
as an anatomical source. In the study by Hirsch et al. , printing materials.
[17]
Volume 9 Issue 4 (2023) 182 https://doi.org/10.18063/ijb.727