Page 475 - IJB-10-5

International Journal of Bioprinting 3D-printed post-otoplasty ear retainer

scores indicate greater satisfaction and compliance. Our 3. Results
survey focused specifically on the device characteristics, 3.1. 3D printing retainer and its accessories
evaluating eight items, including (i) dimension (size); (ii) For the first time, we developed a patient-specific post-
weight; (iii) adjustments; (iv) safety; (v) durability; (vi) otoplasty retainer using 3D printing technology with
ease of use; (vii) comfort; and (viii) effectiveness.
biocompatible material (Figure 2). The retainer was
Among the 20 patients who had undergone ear successfully assembled (Figure 3A–C) and worn by a
deformity corrective surgery, 10 of them wore personalized patient without discomfort (Figure 3D–E).
3D-printed retainers after having their stitches removed
two weeks post-surgery. For comparison, the other 10 3.2. Mechanical tests
patients used external stretching correctors, typically The mechanical comparison between two biocompatible
employed in the early non-surgical treatment of newborn resins is displayed in Figure S3, Supporting Information.
ear deformities to maintain the ear shape (Figure S2, Previous research has indicated that Young’s modulus
Supporting Information). The patients were monitored of auricular cartilage is related to its anatomical location,
23
weekly, and adjustments were made during treatment ranging from 1.41 to 2.08 MPa. Therefore, we selected
as needed. If any complications arose, the treatment was the mechanically superior BioMed Flex 80A Resin for
halted for two to three days to allow the ear to heal. subsequent experiments.
Before treatment and at the final follow-up, 3D scans Figure 4 displays the mechanical tests conducted on the
of the craniofacial region were performed using the BioMed Flex 80A Resin. Figure 4A presents the stress-strain
Spider handheld high-precision 3D scanner (resolution: curves for the 3D-printed resin specimens used for FEA
0.1 mm; accuracy: 0.05 mm; Artec, USA). The scan data with different tensile tests. Figure 4B displays the stress-
were input into Artec Studio 10 software, where the ear relaxation test with 5% and 20% strain at 37°, respectively.
morphology measurement points were determined, Figure 4C features the volumetric compression test of the
including the (i) anterior ear point, at the baseline of the resin used for the retainer. The BioMed Flex 80A Resin
auricle equal in height to the posterior ear point when the exhibited elevated stress at 5% strain over time, whereas
head maintains the eye-ear plane; (ii) posterior ear point, the stress did not decrease at 20% strain. The results
the most protruding point backward at the posterior edge indicate the material exhibits high stress (that increases
of the helix when the head maintains the eye-ear plane; (iii) with time) at low strain (5%) and stable stress (over time)
superior ear point, the highest point of the upper edge of at high strain (20%).
the helix when the head maintains the eye-ear plane; and 3.3. Finite element analysis
(iv) inferior ear point, the lowest point of the earlobe when Finite element analysis (FEA) was conducted on the
the head maintains the eye-ear plane. The measurement ear-shaped retainer after being worn, examining the
function of the software was used to measure ear length, distribution patterns and peak values of different stress
ear width, and the helix-mastoid (H-M) distance on the states (e.g., contact stress, von Mises stress, minimum
affected side before treatment and at the final follow-up. principal stress, von Mises strain, and displacement) on
The ear length is the distance between the superior and the auricle, skin soft tissue, and retainer (Table 2).
inferior ear points; the ear width is the distance between the
anterior and posterior ear points; and the H-M distance is The peak values for contact stress were 291 kPa for
the distance from the most protruding part of the helix to the skin and 394 kPa for the retainer (Figure 5). The peak
the mastoid in frontal view. These indices were measured values for von Mises equivalent stress were 93 kPa for
three times by the same person, and the average was taken. the skin and 97 kPa for the retainer (Figure 6). The peak
The difference in these indices on the affected side before values for minimum principal stress were 94 kPa for the
treatment and at the final follow-up was calculated. skin and 110 kPa for the retainer (Figure S4, Supporting
Information). The peak values for von Mises equivalent
2.7. Statistical analysis strain were 0.052 for the skin and 0.042 for the retainer
Numerical data is presented as the mean ± standard (Figure S5, Supporting Information). The maximum
deviation (SD). Differences among the groups were displacement for both the soft gel and the skin was 0.31
analyzed using Student’s t-test. A p-value < 0.05 was mm, with skin deformation around the contact area of the
considered significant. All analyses were conducted using skin and soft gel retainer ranging from 0.10 to 0.16 mm
Prism 10 (GraphPad Software, USA). (Figure S6, Supporting Information). The relatively

Volume 10 Issue 5 (2024) 467 doi: 10.36922/ijb.3986