Defy Age 
Use of hyaluronic acid fillers for the treatment of the aging face
One of the best feature of HA fillers is that they can be dissolved almost instantly.
HA is a naturally occurring substance, a biopolymer, which exhibits no species and no tissue specificity. HA is an essential component of the extracellular matrix of all animal tissues and is an abundant component of this matrix. HA is highly hydrophilic, that is, it attracts water, and this helps it form large concentrations that can occupy a large volume relative to its mass. When water is drawn into the HA matrix, it has been shown to create a swelling pressure or turgor that enables the HA complex to withstand compressive forces. Thus, it has been found useful as afiller in treating some of the signs of aging.
The first HA as a dermal filler was developed in 1989 by Balazs, who understood the biocompatibility of this class of compounds and lack of immunogenicity. The product was not long lasting, but the revolution had begun.
In the 1980s through the 1990s, US physicians were using primarily collagen-based products for the treatment of lines and wrinkles, folds, and furrows.
In Europe, on the other hand, a revolution was taking shape with the development of the HA (Hyaluronic acid) fillers.
Hylaform® was the first of the HA fillers available for use in the US. It was developed by Genzyme Biosurgery (New Jersey, US) and was distributed by Inamed® (Santa Barbara, CA, US) before Inamed’s acquisition by Allergan, Inc. (Irvine, CA, US) in 2006. Hylaform® was FDA approved in April, 2004.
The next generation of the HA fillers approved for use in the US was Restylane®, FDA approved for use in December, 2003. It is manufactured by Q-Med (Upsalla, Sweden) and is marketed in the US and Canada by Medicis, Inc. (Scottsdale, AZ, US). Restylane® is a non-animal stabilized HA, known as NASHA, produced from the fermentation of equine streptococci. It is cross-linked with BDDA, with a 1% degree of cross-linking.
In fact, in a recent survey conducted by the American Society for Aesthetic Plastic Surgery (ASAPS), the number one non-surgical procedure being performed currently in the US is the injection of botulinum toxin, type A, whereas the fifth most common procedure is now the injection of hyaluronic acid (HA) fillers.
The symptoms exhibited by the aging face are thinning skin, loss of volume (melting of the different fat compartments) therefore sagging skin, hollow eye socket, jowls…
HA fillers play an integral part in the correction of changes associated with aging; especially those associated with the lower -half of the face, from the nasolabial folds, to the vertical lip lines of the lips, the marionette lines around the mouth, and in the thinning of the lip itself. They also can be used for volume enhancement of the cheeks.
Obviously, everyone wants the ideal filler to be easy to inject, to produce reliable and long-term results. Further, the ideal filler would be painless on injection and non-allergenic (no skin tests required), non-carcinogenic, non-teratogenic, and non-migrating once injected into the skin.
Today, a number of HA fillers are available for use as filler materials; many more are under development at the time of writing.
The main differentiators for HA fillers are: source of HA; concentration of HA in each syringe being utilized; the particulate size of the HA; whether the HA is cross-linked; the type of cross-linking agent used in the HA; whether the HA is monophasic or biphasic and whether there is an anaesthetic in the HA syringe. Obviously we would not use the same product to enhance lips (need to stay soft) as we would to recreate volume in the cheeks or even to correct a nose (much thicker product).
The concentration of HA fillers is also important. Those HA fillers with higher HA concentrations displace more tissue and are felt to equate to longer duration of effect. Those HA fillers with concentrations of 20 mg/g or more of HA are now considered ideal.
Given the much wider choice of HA injectables available (cross linked or not, with or without BDDE, totally organic, with succinic acid, etc.), professional advice is paramount.