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

Severe malformations, like microtia, are rare, occurring in Resins are raw materials for SLA additive
0.8–2.4 out of every 10,000 live births. However, simpler manufacturing technology, and they solidify upon UV
anomalies, such as pre-auricular tags and prominent ears, radiation exposure. 13–16 Due to its good biocompatibility,
can affect > 5% of the population. Given the complexity resins are widely used in 3D printing medical devices
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of auricular anomalies, there are various corrective that come into direct contact with human tissue. Resins
surgery techniques to treat the wide variety of congenital can also be printed with very smooth surfaces, reducing
auricular anomalies. Existing corrective surgeries for the need for post-processing and enhancing the comfort
auricular deformities have a high success rate, potentially and functionality of the final product. Furthermore, resins
achieving 80–90% similarity to the corresponding normal can provide adequate strength and toughness, ensuring
ear appearance. However, there are some complications sufficient mechanical compressive strength. 17
of otoplasty for congenital auricular anomalies, such Currently, there are no widely used medical devices in
as hematoma, hypertrophic scar, and recurrence of clinical practice that can maintain the postoperative shape
deformations. Among these, the loss of correction is more of the auricle. Given the significant individual differences
commonly seen in clinical practice, occurring in 12% of in auricle structure, a personalized retainer design based on
cases. This is often attributed to the inherent elasticity of each patient’s auricular data is crucial for maintaining the
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ear cartilage, causing the cartilage to gradually return to shape of the auricle. Additionally, since the retainer must
its initial shape over time. Other factors contributing to adhere to the skin for an extended period, the material
deformation recurrence include suture fatigue, subsequent used needs to offer adequate support strength and good
edema, scarring, and the severity of the initial deformity. 5 biocompatibility. Based on current clinical needs, we have

Ear molding techniques are widely used in neonatal developed a personalized postoperative auricle-shaped
patients to correct deformities. It is a non-surgical retainer utilizing structured light scanning data for the
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intervention that gradually reshapes ear cartilage over first time. Through innovative design, the retainer is easy
several days to weeks by applying continuous tension. It to put on and take off while effectively securing around
can achieve satisfying results as ear cartilage is flexible in the auricle. In this study, we used a novel biocompatible
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newborns. The estrogen content in newborns gradually elastomer BioMed Flex 80A to print the retainer, providing
adequate elasticity and support for sub-anatomical units
decreases as they grow, which causes the auricle cartilage of the auricle. Furthermore, we performed mechanical
to harden, increasing the elasticity of ear cartilage and tests to evaluate the performance of our material. After
the tendency to return to the original morphology after acquiring typical scanning data from one clinical case, we
corrective surgery, especially in older patients. Therefore, successfully designed and manufactured a retainer and its
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post-corrective surgery support for elder patients is accessories. To further investigate the effect of the retainer,
essential, and postoperative molding is proven to be effective we utilized finite element analysis (FEA) to simulate the
in some post-otoplasty cases using silicon supports. 10 stress created by the retainer on the surface of the ear
Stereolithography (SLA) 3D printing relies and mimic the biomechanical behaviors of both ear and
on the controlled solidification of a resin through retainer. Moreover, the prototype was successfully worn by
photopolymerization. SLA can achieve very high the patient and achieved a satisfying result.
resolution and precision in the printed parts, which is
critical for fabricating detailed and accurate retainers. The 2. Methods
process involves focusing an ultraviolet (UV) laser source 2.1. Data acquisition
onto the resin surface to induce photopolymerization A handheld structured light 3D scanner (Artec Spider
according to a computer-aided design (CAD), resulting Scanner; Artec Group, Luxembourg) was used to capture
in resin solidification. The layer-by-layer curing process the structure of the outer ear from all angles. Prior to
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enables fine control over the dimensions and intricate scanning, the 3D scanner was preheated, in accordance
details of the final product, essential for ensuring a proper with the manufacturer’s guidelines, to ensure optimal
fit and effectiveness of the retainers. Besides, SLA provides accuracy. Various angles were used in smooth motion
a superior surface finish compared to other techniques to comprehensively capture the entire auricular area.
like fused deposition modeling (FDM) or digital light Real-time fusion enabled visual monitoring of the scan’s
processing (DLP). The smooth surface finish reduces the completeness during and immediately after the process.
need for extensive post-processing, making the retainers A range indicator displayed the distance between the
more comfortable for patients to wear and enhancing their scanner and the object in Artec Studio 11 (Artec Group,
aesthetic appeal. 12 Luxembourg), consistently maintaining a working distance

Volume 10 Issue 5 (2024) 463 doi: 10.36922/ijb.3986