Dermal Fillers

What are the filler substances?

Injectable fillers fall under six headings:

1. Hyaluronic acid
2. Calcium hydroxylapatite (CaHA)
3. Poly-L-lactic acid (PLLA)
4. Polycaprolactone
5. Fat fillers (autologous — taken from the person themselves)
6. Permanent fillers

Hyaluronic acid

This is the material most often chosen in making fillers. It is a glycosaminoglycan with a polysaccharide structure — a molecule found naturally in the body. It provides moisture and nourishes the skin by holding up to 1000 times its own molecular weight in water.

It is generally obtained from bacterial culture (fermentation of Streptococcus equi). Those produced from animal sources are obtained from rooster comb. It received FDA approval in 2003 and requires no allergy test.

If it comes into contact with heat, the monomers that form can cause inflammation and can make the product disappear sooner. For this reason it is stored at room temperature.

Poly-L-lactic acid (PLLA)

This is the raw material of the absorbable suture used in surgery. In 2004 it was approved by the FDA as a filler material for correcting loss of facial fat tissue due to HIV treatment.

It does not give volume directly; it stimulates the cells called fibroblasts (the cells that produce collagen) and so increases the production of type 1 collagen. Its effect lasts on average 18–24 months.

It has been found to carry a high risk of forming papules and nodules under the skin (small firm lumps) in the areas around the mouth and the eyes; care is advised in these areas.

Calcium hydroxylapatite (CaHA)

Bioceramics in particle form are prepared in a carrier called carboxymethyl cellulose. Its capacity to hold water is very low.

When the carrier begins to disappear within 2–3 months, the microspheres left behind start a foreign-body reaction; this stimulates the fibroblasts and so increases collagen. It received FDA approval in 2006; it lasts on average 12–18 months.

Polycaprolactone

This is a medical polymer used in medicine for about 20 years as suture material and wound dressing, which dissolves completely in the body leaving no residue. It stimulates the production of type 1 collagen, so that a longer-lasting renewal is achieved through the newly formed collagen.

Fat (autologous) fillers

These are obtained from the person's own tissue. They are used to restore a hollowed face and to address deep lines. Because of the stem cells they contain, which nourish the skin, they give vitality and radiance.

Their most important advantage is that they do not cause an allergic or foreign-body reaction.

But they are not recommended under the eyes or in the lip area. They are a suitable option for people who have had severe weight loss and have marked hollowing of the face.

What determines how long a filler lasts?

The same substance does not last the same time in everyone. The factors that affect how long it lasts:

• Whether the area it is applied to is mobile
• The depth of injection — filler placed into muscle disappears sooner
• The rheological properties of the filler (its flow and resistance behaviour)
• The amount of cross-linking — more cross-linking means it lasts longer
• The person's way of life
• Alcohol and smoking
• Excessive exercise
• Illnesses and weight loss

Why does knowledge of anatomy matter so much?

The face has a complex anatomical structure. Before treatment, the characteristics of the area to be treated — the skin, the tissue beneath it, fat tissue, muscle tissue, bone and the distribution of vessels and nerves — must be reviewed.

Some of the arteries in the face are branches of the artery of the eye. The venous structures also matter: the middle temporal vein in the temple area drains into the large vein in the neck. For this reason injections made in the wrong direction can lead to a pulmonary embolism.