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International Journal of Bioprinting 3D printing prosthesis for palatal fistula

manufacturing synergy provide a new treatment method. In combination with the excellent biocompatibility and
mechanical properties of polyurethane, this study proposes a new strategy for treating refractory palatal fistula and
extensive palatal defects, aiming to reduce the difficulty of prosthesis fabrication and maximize the restoration effect
and quality of life for patients.

Keywords: Prosthesis; 3D printing; Computer fluid dynamics; Polyurethane; Photocuring

1. Introduction structures mainly relies on patients’ subjective perception,
such as their initial feeling of stability and positioning, the
Palatal fistula, also known as palatal cleft, is a clinical leakage of water, and speech conditions after wearing the
condition characterized by tissue defect in the area where device. In the prosthesis design and production process,
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the maxilla protrudes into the uvula. The communication it is impossible to pre-evaluate their repair effects. The
between the oral and nasal cavities caused by palatal quality and precision mainly depend on the subjective
fistula can lead to functional impairments such as nasal judgment of technicians, which contributes to an increase
1,2
air leakage, nasal discharge, and speech disorders. in the number of patient visits and material waste. An ideal
These functional impairments can significantly impact prosthesis should be able to transform the open cavity
3-5
patients’ psychological well-being and social activities. flow on the side of the patient’s defect into closed cavity
Although palatal fistula can be repaired through surgical flow, effectively changing the flow characteristics, restoring
reconstruction, a second operation is often required the airtightness of the airway, and improving speech
due to the damaged donor site tissue and postoperative function. In recent years, computational fluid dynamics
complications such as vascular crisis, bleeding, and airway (CFD) analysis, which analyzes the flow of liquids or gases
obstruction, making postoperative management complex inside or around models, has been widely used in research
6,7
and patient acceptance low. Prosthodontic rehabilitation on drug delivery in the respiratory system and sleep
8
is the most used non-surgical method for repairing apnea disorders. 16,17 By employing numerical simulation
palatal fistula. Traditional prosthesis fabrication involves methods to calculate the airflow field in the upper airway,
modeling, wax carving, and resin molding, which usually researchers can construct a more accurate and detailed
require collaboration between experienced maxillofacial upper airway mechanics model that is not constrained by
prosthodontists and dental laboratory technicians. the complex structure of the upper airway. Therefore, if the
9,10
However, due to the complex and diverse structures airflow pattern in the defect cavity after the repair of the
of the defect area, conventional prosthesis fabrication designed prosthesis can be simulated and analyzed through
techniques are unable to fabricate structures with complex 3D reconstruction and numerical simulation before the
morphology in high precision.
design and production of the device, the accuracy of the
Moreover, the fabrication process is often tedious and prosthesis model can be significantly improved. Analyzing
time-consuming. Digital design has been widely applied the airflow field in the upper airway of patients before and
11
in oral rehabilitation in recent years due to its rapid and after the repair using CFD technology makes it possible
accurate characteristics. It has gradually found utilization to construct an accurate and detailed airway mechanics
in designing and fabricating prosthetic restorations. 12,13 model that complements and cooperates with digital
Previous studies have reported that digital three- design. 18,19 Based on the results, adjustments can be made
dimensional (3D) design and 3D printing techniques to the anatomical shape design, height, thickness, and other
can fabricate prosthetic restorations to repair defects in prosthesis parameters, providing a parameter basis for the
the nose, orbit, cheek, and other maxillofacial regions. pre-evaluation of the sealing effect and the optimization
1
However, there are still some challenges in the 3D design design of the prosthesis structure.
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of digital prosthetic restorations. The prosthesis can only Soft materials, such as silicone rubber, acrylates, and
be designed by directly constructing the surface using thermoplastic polyurethane and rigid materials, such as
software or matching healthy tissue data from a prosthesis polymethyl methacrylate, are mainly used in the clinical
database for tissue defects from which a symmetrical fabrication of prosthesis. Among them, silicone rubber
20
mirror image cannot be obtained. Therefore, it is difficult material has good biocompatibility, soft texture, and
to evaluate the adaptability and closure of the defect area elasticity. It is a material with comprehensive properties
based on the restoration’s anatomical morphology. widely used in maxillofacial defect repair in clinics. 21,22
Currently, there are no objective and standardized However, silicone polymers have two main drawbacks:
parameters for the production standards of prosthesis color degradation and instability, which are caused by
23
structures. The evaluation of the repair effect of prosthesis exposure to UV rays, air pollution, and humidity. There
Volume 10 Issue 4 (2024) 264 doi: 10.36922/ijb.2516