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Actualizing Hybrid Pressure and Silicone Therapies with 3D Printing and Scanning
feature of this phase is the granulation tissue formation treatment results except when the patient is bathing
which includes fibroblasts, myofibroblasts, loose or the garment needs to be washed . Silicone sheet
[24]
connective tissue, and capillaries. Extracellular matrix is therapy is the application of a thin silicone sheet onto the
excessively produced by fibroblasts and myofibroblasts HS which increases the skin temperature, hydrates the
for structural support for nascent capillaries which scar, and facilitates the polarization of scar tissues, thus
results in hypertrophic scars (HSs) formation [4-6] . At the contributing to a reduction of the HS [25-31] . Furthermore,
end of this phase, the wound becomes an immature scar silicone sheets can be used as a protective barrier against
which is fragile and has a low tensile strength. The last the external environment to prevent secondary damage or
phase of wound healing is the remodeling which turns infection of the scar [27,32] . The differences between silicone
the immature scar into a mature scar and this phase can sheets and silicone gel are the degree of crosslinking and
last for 2 years. The excessive extracellular matrix is polymerization. Silicone sheets have a longer and stronger
remodeled from the weak and disordered type III collagen polymer chain; therefore, they cannot be spread onto
into the stronger and more ordered type I collagen by skin like silicone gel . Although proven to be effective
[26]
matrix metalloproteinases. With the passage of time, treatments for HSs, pressure therapy, silicone sheets, and
the scar will be flattened because the newly synthesized silicone gel have their inherent limitations. For example,
collagen is weaved into the stable fibrils. Furthermore, the complexities of the human body shape is a barrier for
the cellularity and vascularity of wound will be reduced the pressure garments to exert pressure onto the concave
due to the activity of matrix metalloproteinases . parts of the body . Moreover, silicone sheets do not
[7]
[33]
Due to the protrude and erythematous appearance work well on joints, such as elbows and knees, because
of the hypertrophic scarred skin, the quality of life of they might debond from the body part during movement
HS patients can even be significantly affected as the that requires joint use and a large range of motion.
[8]
scarring may reduce self-esteem or even affect the mental Although it is not a burden for the patients to apply the
health of the patient due to their esthetically unpleasing silicone gel twice a day, it is important to note that the
appearance . This problem is more obvious in female gel might be easily wiped off during daily activities.
[9]
patients than male patients . Apart from cosmetic issues, Therefore, clinicians need to consider the location of
[8]
inappropriately managed HSs can cause functional the HS and determine which treatment should be used to
difficulties; for instance, a limited range of motion is obtain maximum treatment efficacy. In some cases, the
commonly found due to the reduced elasticity of the treatments can be combined; for instance, silicone sheets
skin and HS hardened tissues . The low elasticity of and pressure therapy are often used together and proven
[10]
hypertrophic scarred skin is due to less elastin production to provide a better effect in reducing scar thickness and
in comparison to normal tissue [11,12] . Therefore, HSs can increasing scar pliability [26,34,35] . However, the size of
be said to be the most challenging problem in wound the silicone sheet is usually larger than that of the HS to
healing and rehabilitation process. In 2015, 67 million ensure that it is securely adhered to the skin, which may
burn injuries were caused by fire and other sources of have negative impacts when covering healthy skin . The
[26]
high heat worldwide and around 70% of burn patients negative impacts include excessive sweating, pruritus or
develop an HS . Another study also found that more even contact dermatitis [26,36] . To date, there have been few
[13]
than 70% of the patients in Hong Kong form an HS after quantitative studies done on integrating pressure, silicone
surgery . The high prevalence of HS formation with sheets, and silicone gel as a form of treatment to control
[14]
a lengthy treatment process can be a heavy burden on the abnormal growth of hypertrophic scarred tissues.
health care systems. In the United States, the cost for The advancement of three-dimensional (3D)
treating and managing scars is estimated at around US$ printing, 3D scanning and computer-aided design, and
20 billion every year . manufacturing software has led to a variety of applications
[15]
Pressure, silicone sheet, and silicone gel therapies in the medical field, such as artificial implants, orthoses,
are the most common non-invasive treatments for HSs. and prostheses, which can be customized and 3D printed to
For decades, pressure therapy has been used to accelerate fit the needs of individual patients [37-39] . For example, Kang
the maturation of HSs and improve their appearance [16,17] . et al. demonstrated the ability of creating vascularized
[40]
A number of studies conclude that exerting a continuous cell-laden bone constructs with tunable mechanical
pressure of about 25 mmHg can inhibit the growth properties using integrated tissue-organ printer. It is worth
of HSs and encourage their maturation [16,18-21] . This is noting that the 3D printed face shields play a significant
because exerted pressure may reduce the blood flow to role during the outbreak of the COVID-19 in 2019 [41,42] .
the hypertrophic scarred tissues so as to limit nutrients Hale et al. also developed bespoke orthoses for neck
[43]
and oxygen supply to the tissues, thereby effectively stability using 3D printing and scanning technologies. To
reducing the production of collagen [22,23] . Therefore, improve the control over the pressure distribution or heat
pressure garments should always be worn for optimal transfer of custom-engineered products, biomechanical

124 International Journal of Bioprinting (2021)–Volume 7, Issue 1