In this article, we will discuss the characteristics of injectable soft-tissue fillers, which are used to restore facial volume and youthfulness. In the past several years, there has been a paradigm shift in the approach to the aging face. Historically, physicians would tailor filler treatments to target specific lines and wrinkles without addressing the total volume loss that contributed to their development. Physicians have since taken a step back and redirected the treatment of the aging face to focus first on global correction, followed by targeted therapy. Injectable soft tissue fillers are an integral part of cosmetic dermatology and have significantly changed the way physicians address facial aging.
Increasing emphasis is being placed on one’s physical appearance, contributing to the recent remarkable growth of the cosmetic industry. To put this in perspective, nearly $13.5 billion was spent on cosmetic procedures alone in 2015. Dermatology and plastic surgeons alike are experiencing significant demand, specifically for non-invasive, low-risk procedures with minimal downtime. When they initially became available, cosmetic procedures were limited to the wealthy and those in the public eye. But today, these procedures are widely available and have allowed the public to invest more money in their physical appearance. A broad swath of the population is now interested in pursuing a more refreshed and rejuvenated appearance via soft-tissue fillers.
Many people desire to have some type of cosmetic procedure, but avoid doing so due to fear of the associated risk and significant downtime. This does not hold true for modern cosmetic medicine. Since the mid-1990s, non-surgical procedures have gained popularity and have surpassed the demand for invasive cosmetic procedures. Non-surgical cosmetic procedures are those in which the skin remains intact – no cutting or general anesthesia necessary. These are an attractive option for the patients who do not want to undergo an invasive, risky, and time-consuming procedure.
According to a survey conducted by the American Society of Plastic Surgeons between 1997 – 2013, the total number of non-surgical cosmetic treatments performed during that time period increased by more than 500%. The top 4 cosmetic procedures performed in 2015 were botulinum toxin, soft-tissue fillers, chemical peels, and laser hair removal.
In 1893, the first filler procedure was performed to correct facial scars using autologous fat. It was at this time that the concept of “filling” was introduced. The benefits of this procedure were short-lived, and the side effects were significant. Much later, bovine collagen became the first soft tissue filler approved by the Food and Drug Administration (FDA) for the correction of facial lines and wrinkles. Despite bovine collagen’s improved filler characteristics, longevity remained limited and skin testing was a requirement to avoid allergic reactions after injection.
Most recently, hyaluronic acid fillers were developed to improve longevity, tolerability, and side-effect profiles. Soft tissue fillers have revolutionized the field of cosmetic medicine, with numerous HA-based products now saturating the market. HA fillers are used worldwide and offer a durable alternative to bovine collagen filler with little to no required downtime and a very low incidence of associated side effects.
Commonly referred to as the ideal filler, hyaluronic acid (HA) is durable, well tolerated, non-permanent, natural, and has the ability to be reversed in the event of undesirable side effects or results. It is also a substance that is made naturally within the human body, providing structural support to the skin by binding collagen and elastin fibers.
The HA used in cosmetic fillers is derived from Streptococcus bacteria. When injected into the skin, HA filler binds water molecules, plumping to create the appearance of volume for 6-18 months, depending on the type of product used. Additionally, numerous studies have demonstrated that HA fillers contribute to new collagen production in the deeper portion of the skin (dermis). Over time, HA fillers are slowly degraded by the body’s own enzymes, requiring additional treatments to restore and maintain the desired results.
HA fillers differ amongst one another by their degree of molecular cross-linking, concentration, and particle size. These features contribute to the physical properties (viscosity, duration, and lift capacity) of each filler. The more highly cross-linked the filler, the greater the durability and lift capacity of that product. For example, a highly concentrated HA filler with a high amount of cross-linking will provide more structural support and longevity than a low concentration HA filler with a moderate amount of cross-linking.
You may be asking yourself, then, why all fillers are not maximally cross-linked and concentrated? The reason behind this is that different regions of the face require different characteristics in order to achieve a natural, rejuvenated appearance. Placement of a highly cross-linked, very concentrated filler in thin-skinned regions such as the lips and under-eyes (tear troughs) may result in swelling, nodularity, and an unsightly bluish discoloration (Tyndall effect). Therefore, in such areas, selecting a moderately cross-linked filler with a low to moderate concentration of HA is typically more suitable. Less cross-linked fillers also have the ability to spread homogeneously throughout the skin, whereas moderate to highly cross-linked fillers tend to remain at the specific site of injection with little ability for spread throughout the surrounding skin.
Highly cross-linked fillers are excellent at “lifting”. As we age, we lose a significant amount of volume in the anterior cheekbones. This volume loss causes the medial cheek fat pad to descend, contributing to an “aged” appearance. A highly cross-linked filler placed in the location of the volume loss (mid-upper cheek) will act as a support beam to lift the cheek, indirectly lifting and improving the appearance of lower facial wrinkles. At the same time, the placement of a thinner, less cross-linked filler in the tear troughs (under the eyes) will act as a cushion to increase the distance from the underlying blood vessels. This technique can reduce the appearance of dark under-eye circles while also giving the skin a more hydrated and volumized appearance.
Highly-concentrated HA fillers absorb more water than less concentrated fillers and may cause significant post-procedural swelling. When treating areas of thin skin, such as the tear troughs (under the eyes), an HA filler with a lower concentration is ideal to avoid unsightly and uncomfortable swelling.
In conclusion, there are many factors that your physician must consider when selecting the most appropriate modality for your cosmetic procedure. The goal of this article is to introduce the basic science behind facial fillers, sparking a more educated conversation between you and your dermatologist.