Page 277 - IJB-10-4

International Journal of Bioprinting 3D printing prosthesis for palatal fistula

cylindrical support at the position requiring bearing load. organs (heart, liver, spleen, and kidney) were removed and
The wavelength of the adopted ultraviolet (UV) light was immediately fixed in 10% formalin for histological analysis.
405 nm; the thickness of each layer was 0.05 mm; the After 72 h, samples were dehydrated, paraffin-embedded,
exposure time was 2.5 s; the bottom consisted of 10 layers; sectioned, and cured. Hematoxylin–eosin (H&E) staining
the irradiation time was 5 s; the lifting distance was 5 mm; was conducted prior to observing the pathological changes
and the lifting speed was 50 mm/min. During the printing under a light microscope (Olympus BX53, Tokyo, Japan).
process, the structure under printing was crosslinked layer
by layer, under the irradiation of UV light. 2.7. Statistical analysis
SPSS version 26 (IBM, Chicago, USA) statistics software
2.5.12. Post UV treatment was employed for statistical analysis. All results are
After printing, the prosthesis was placed in a post- expressed as mean ± standard deviation (SD). We analyzed
processing machine (CREALITY UW-02, Shenzhen, group comparisons using one-way ANOVA, followed by
China) and subjected to continuous UV exposure for Tukey’s post hoc test, with SPSS 19.0 (SPSS Inc., Chicago,
enhanced curing and simultaneous washing. USA). A p-value below 0.05 was deemed statistically
significant (*p < 0.05, **p < 0.01). All experiments were
2.6. Biocompatibility tests of PU elastomers repeated for at least three times.

2.6.1. In vitro cytocompatibility and morphological
evaluation of L929 cells 3. Results and discussion
According to the standard GB-T 16175-2008, the standard 3.1. Establishment of the animal model of palatal
specimen was prepared and immersed in the culture fistula and 3D reconstruction
medium for 30 days to obtain the extract. The in vivo biological evaluation using animal experiments
We analyzed the viability, morphology, and is the key to developing materials for clinical applications. 35,36
proliferation of L929 to evaluate the biocompatibility As Figure 1A shows, the palatal fistula healed after 1 week.
of the PU elastomers. The L929 was evaluated by means Figure 1B shows the CBCT of the healed palatal wound,
of live/dead staining to identify the biocompatibility of which proves the successful establishment of the palatal
the PU elastomers. The numbers of live and dead cells fistula. The airway mask (Figure 1C) demonstrates the
per microscopic field were observed under a fluorescent connection of the upper airway on the affected side to the
microscope (Eclipse Ts2R, Nikon, Tokyo, Japan) using 480 oral cavity.
nm and 520 nm filters, respectively. 3.2. Design of prosthesis and CFD
An Alamar Blue assay was performed to quantify L929 analysis-guided design
viability in the culture of extracts of different groups of PU The model of the upper airway before repair (Figure 1D)
elastomers. The cells were seeded in the extracts of each and the model of bone were extracted using the Mimics
group and cultured for 1, 3, and 5 days. After incubating 21.0 software (Figure 1F). The models were optimized in
the cells at 37°C for 4 h, we collected 100 μL of supernatant Geomagic 2017 software (Figure 1E). According to the
and obtained absorbance reading at 570 nm using a upper airway model, bone model, and soft tissue, the shape
microplate reader. of speech aid prosthesis was designed. We assembled the
prosthesis model subsequently to check for matching and
2.6.2. In vivo biocompatibility evaluation completeness (Figure 2A).
Eight-week-old male Sprague–Dawley (SD) rats were
purchased from the Laboratory Animal Center of Correct meshing and mesh quality are essential for
37,38
Southern Medical University (Guangzhou, China) and accurate CFD simulations. The upper airway models
randomly divided into two groups (n = 6). After being before and after repair were imported into the Ansys
injected with an anesthetic called “Su-Mian-Xin Ⅱ” 2021 software to divide the CFD model mesh. As shown
(0.8 mL/kg; Shengxin, Institute of Veterinary Medicine, in Figure 2D, the mesh is wonderful, and the analysis of
Changchun, China), the rats were sterilized with 75% mesh quality showed that almost all the Element Metrics
alcohol and iodophor. Two incisions were made on each are above 0.5 (Figure 2E).
spine side to bluntly separate the mucosal layer to form a The preliminary evaluation of the printing accuracy
subcutaneous implant pocket. The light-curable PU sheets was conducted using a 3D model of the single-layer porous
and MDX-4210 silicone rubber (Dow Corning, USA) as scaffold. Each pore in the scaffold measures 500 microns
control were implanted at each site on both sides of the in length and 300 microns in width. Subsequent scanning
spine of SD rats. The animals were sacrificed at the end of electron microscopy (SEM) tests revealed clear visibility
the fourth and eighth weeks. Perigraft tissues and major of the printing filaments and obvious pores (Figure 2F),

Volume 10 Issue 4 (2024) 269 doi: 10.36922/ijb.2516