Page 187 - IJB-9-4

International Journal of Bioprinting 3D-printed middle ear prostheses

Figure 3. First-generation 3D-printed PORP. (A) Successfully 3D-printed prosthesis (macro photography by M.Sc. (Tech) Pekka Paavola). (B) Structural
deviation in the cup. (C) Broken shaft.

inspection and imaged with micro-CT. After that, the Table 1. Accuracy of 3D printing in the first-generation PORP
dimensions of the PORPs were measured individually. In
the 3D model, the shaft diameter and the functional length 3D model Sample no. Shaft diameter Functional length a
(mm)
(mm)
of the prostheses were designed to be 0.400 mm and 1.893
mm, respectively. Table 1 shows the mean measures of the 0.400 1.893
14 prostheses together with their standard deviations (SD). Prostheses 1 0.439 1.931
On average, the printed prostheses had shaft diameter 2 0.432 1.935
54 μm thicker and functional length 64 μm longer than in 4 0.444 1.927
the model. The SD for shaft diameter was 21 μm and 57 μm 8 0.406 2.012
for functional length. As for accuracy and reproducibility, 12 0.447 1.966
the SDs of the printed PORPs as well as size differences
when comparing the printed PORPs and the 3D models 13 0.480 2.075
are close to the micro-CT’s imaging resolution (40.09 μm), 14 0.486 1.885
suggesting that 3D printing of PORPs is precise. 15 0.460 1.928
After visually analyzing the first-generation 3D-printed 16 0.442 1.942
PORPs with a success rate of 54%, we decided to increase 17 0.474 2.062
the shaft diameter from 0.400 to 0.600 mm. Also, cup 19 0.465 1.871
flanges were made larger in order to prevent sharp edges 21 0.471 1.966
in printing. In addition, as some of the PORPs’ plates 27 0.461 1.967
were broken when detaching them from the supporting 30 0.444 1.929
structures, we reduced the hole sizes in the prosthesis Mean
plate. In Figure 4A, a second-generation PORP is shown 0.454 1.957
in 3D model format, and, in Figure 4B, a 3D-printed SD 0.021 0.057
second-generation PORP is photographed by the photo Range 0.406–0.484 1.871–2.075
stacking technique. When printing this second-generation 14 prostheses analyzed with micro-CT with their mean and standard
PORPs, 129 out of 130 prostheses were classified as deviation (SD).
successfully printed. Only one prosthesis was classified a Functional length means distance from the bottom of the cup part to
as unsuccessfully printed due to a broken shaft. Thus, the the outer surface of the plate.
modifications mentioned before improved the printing tympanotomy. The METF was measured with intact
success rate significantly.
ossicular chain, without incus, and with a titanium Kurz
The functionality of the second-generation 3D-printed Clip Partial Flexibal prosthesis or a second-generation
PORPs was tested in LDV (Figure 4A). Figure 4D and E 3D-printed PORP. In Figure 5, mean (solid line) METFs
demonstrate a 3D-printed PORP placed between stapes measured in different ME transduction modes are plotted
head and tympanic membrane through posterior with their SDs (colored area). Displacement (in nanometers;

Volume 9 Issue 4 (2023) 179 https://doi.org/10.18063/ijb.727