An injectable filler is defined as any substance that can be injected into or under the skin to fill out a wrinkle or depression. These products are considered off-the-shelf in that they are commercially prepared and ready to use.
The original injectable filler was collagen and for many years was the only product in this category, which makes it the standard against which all other products are compared. Collagen has largely been supplanted by other longer lasting products, but it still has its proponents. In a recent review, the advantages listed were ease of use, versatility and long safety record. These claims are true but all of the injectable fillers have excellent safety profiles when properly used. It is therefore hard to justify in my mind the use of collagen because it is only marginally less expensive but lasts about half as long as most other products.
The most popular fillers today are those that contain hyaluronic acid, a substance which can be found in the cell matrix of the skin. Hyaluronic acid (HA) is identical across all species, whether it is found in a human or animal, so allergic reactions are not a concern. HA can be injected into superficial wrinkles or deep folds on the face or to enhance lip size, and it is most often used for wrinkles that will not respond to Botox injections, although it can also be used after Botox. The most popular products are Restylane and Juvederm. Restylane typically lasts 4-6 months and tends to last longer in areas of less muscle activity. Juvederm may last up to 9 months but it is more expensive.
An alternative longer-lasting product is Radiesse, which contains calcium hydroxyappetite in a suspension gel. The components of calcium hydroxyappetite occur naturally in the body so once again allergic reactions are rare. It is not as soft as HA and therefore must be injected at a deeper level, which makes it unsuitable for more superficial wrinkles. It is approved for use in the deep folds around the mouth but it has been used in other areas as well. It may last up to one year.
The potentially longest-lasting substance is Artefill, which only recently became available in the US. Artefill contains microspheres of non-absorbable methylmethacrylate in a suspension of collagen. The expectation is that as the collagen is absorbed by your body, it is replaced by your body's own collagen. A second booster dose will be needed in some patients who do not form enough collagen. It has been available in Europe and has been reported to last for years and it can be permanent. The permanence can be a disadvantage, however, if it is improperly injected and creates a visible nodule. Assuming it lives up to its published reports, it will be a very popular choice because it will eliminate the need for repeated injections.