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on its depth and is classified according to degrees. First degree burns
are superficial and do not result in scarring. Second degree burns,
are further classified as Type-A, with complete aesthetic restoration
and Type-B that do not necessitate any surgical intervention, but
will result in some skin discoloration after healing. Third and
fourth degree burns involve the full thickness of the skin and require
reconstructive surgery to remove scarred tissue or repair disfiguration
of the face or body. Mosaic burns include different degrees of depth
[11]. HA provides increased hydration, activates neocollagenesis
and neoangiogenesis and as a result, it is widely used to treat first
and second degree burns with excellent aesthetic results either as
a dressing or a cream. The benzyl esters of HA have been studied
thoroughly as HA derivatives [12, 13].
7.2.2 Hyaluronic Acid as a Filler and Skin Biorevitaliser
Facial characteristics are defined by the skin, muscles and bones.
Over the years, the face loses its youthful appearance. Body weight,
hormonal changes, ultraviolet radiation, smoking, and gravity lead
to the appearance of depressions and wrinkles. In addition, the loss
of the skin's elasticity becomes apparent after the age of 30. Areas of
the face most affected are: the periorbital, malar, forehead, temporal,
glabellar, mandibular, mental and perioral zones [14-16].
HA injections can restore the natural and youthful appearance
of the skin. This minimally invasive procedure restores tissue
volume, reduces wrinkles, and fills the depressed areas by local
absorption. The use of HA as a skin filler became popular in the
mid-1980s and, according to the ASAPS, it is considered to be
the fastest growing, non-invasive, procedure in the United States
[17]. Filler HA is a viscous, transparent gel, which can be injected
through a small gauge (G) needle, typically of 23-27 G. It provides
increased volume and skin hydration due to its hydrophilic nature.
Deep wrinkles require a high concentration of HA (approximately
25 mg/ml), while shallow wrinkles are typically treated with a
lower concentration (5 mg/ml). HA filler lasts approximately
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