Dermal fillers are injectable medical devices that restore volume and smooth wrinkles in the face and hands. The FDA classifies them as medical device implants, approved for areas including the lips, cheeks, chin, nasolabial folds (the lines running from your nose to the corners of your mouth), and the back of the hands. They work by either physically filling space under the skin, stimulating your body to produce new collagen, or both.
How Dermal Fillers Work
Fillers restore lost volume through two basic mechanisms. The first is straightforward: the injected material physically occupies space beneath the skin, pushing tissue outward to smooth a wrinkle or plump an area that has thinned with age. The second is biological. Certain filler materials trigger a mild inflammatory response that activates your skin’s collagen-producing cells, gradually building a natural scaffold of new tissue around the injection site.
Some fillers rely on just one of these mechanisms, while others use both. Hyaluronic acid fillers, for example, work primarily by binding water and filling space. They hydrate the surrounding tissue while providing immediate structural support. Calcium hydroxyapatite fillers deliver an instant volume boost from their gel carrier, then continue working over months as their microspheres stimulate new collagen growth. Poly-L-lactic acid takes the opposite approach: the initial volume you see after injection is mostly from the liquid suspension, but the real results develop gradually as your body builds collagen around the particles.
Types of Filler Materials
Hyaluronic acid is by far the most common injectable filler in the United States. It’s a sugar-based molecule that occurs naturally in your skin and joints, and the synthetic version used in fillers is chemically crosslinked to make it last longer in tissue. Results typically last 6 to 12 months before the body gradually breaks the material down.
Beyond hyaluronic acid, several other materials are FDA-approved:
- Calcium hydroxyapatite is a mineral compound suspended in a gel. It provides both immediate filling and long-term collagen stimulation, with effects lasting approximately 18 months. It’s generally avoided in the lips because repeated muscle contractions can cause the material to migrate and form visible nodules.
- Poly-L-lactic acid (PLLA) is a biostimulatory filler that works primarily by activating collagen production rather than providing instant correction. Results develop over weeks to months and can last up to 2 years.
- Polymethylmethacrylate (PMMA) consists of tiny microspheres suspended in a collagen gel. Unlike other fillers, it is considered semi-permanent because the microspheres are not absorbed by the body.
All of these except PMMA are classified as absorbable, meaning the body breaks them down over time and they eventually disappear.
Where Fillers Are Injected
Fillers can be placed at different depths depending on the treatment goal and facial area. Two common targets are the layer just above the connective tissue sheet that covers facial muscles and the layer just below it. Deeper injections near the bone work well for structural support in the cheeks and chin, while shallower injections suit fine lines and lip borders.
The most popular treatment areas include the cheeks (to restore midface volume), the nasolabial folds, the lips, the jawline, the chin, the under-eye hollows (tear troughs), and the temples. Each area requires different injection techniques. Lips and nasolabial folds often use a threading approach where filler is deposited in a line as the needle moves through tissue. Cheek augmentation may involve a fanning technique with multiple passes from a single entry point. Temple hollowing is often treated with a single deposit of filler placed deep beneath the muscle layer.
What the Procedure Feels Like
Most filler appointments are quick, often taking 15 to 30 minutes depending on how many areas are treated. Many filler syringes come premixed with a numbing agent, and your provider may also apply a topical anesthetic cream beforehand. You’ll feel pressure and a pinching sensation at the injection sites, but the discomfort is generally mild.
You can return to most normal activities the same day. Swelling is the most common side effect, occurring in roughly 41% of people who receive hyaluronic acid fillers. Bruising affects about 11%. Both are temporary. Avoiding intense exercise for the first 24 to 48 hours helps minimize swelling and bruising. Most people see the final result within one to two weeks, once the initial swelling has settled.
Risks and Complications
Mild, short-lived side effects like swelling, redness, and tenderness at the injection site are expected. More concerning but rare complications involve the filler accidentally entering or compressing a blood vessel, which can cut off blood flow to surrounding tissue. In the most severe cases, vascular occlusion has caused skin death (necrosis) and even blindness. A meta-analysis of reported vascular complications found that blindness was the most frequently documented serious event, and among those cases, only 28% experienced partial or total recovery.
These serious outcomes are uncommon, but they underscore why provider expertise matters. Filler should not be injected near an active infection, whether that’s a skin infection, a dental infection, or an active cold sore outbreak near the lips. Anyone with a known allergy to the filler material or to the numbing agent mixed into the syringe should avoid that product.
One Key Advantage of Hyaluronic Acid
A major reason hyaluronic acid dominates the filler market is that it can be reversed. An enzyme called hyaluronidase, which has been used in medicine since 1949, breaks down hyaluronic acid by snapping apart the chemical bonds that hold the molecule together. If a filler produces an undesirable result, causes a lump, or contributes to a vascular complication, a provider can inject hyaluronidase to dissolve it. The filler breaks down rapidly, often within hours.
This reversibility does not extend to other filler types. Calcium hydroxyapatite, poly-L-lactic acid, and PMMA fillers cannot be enzymatically dissolved. If a problem arises with one of these materials, management is more complex and may require waiting for the body to absorb the filler naturally or, in some cases, surgical removal. For many people, especially those trying fillers for the first time, the safety net of reversibility makes hyaluronic acid the most practical starting point.
How Long Results Last
Duration depends entirely on the material used, the treatment area, and individual factors like metabolism. Hyaluronic acid fillers last roughly 6 to 12 months. Areas with more movement, like the lips, tend to break filler down faster than relatively static areas like the cheeks. Calcium hydroxyapatite lasts about 18 months. Poly-L-lactic acid results can persist for up to 2 years, partly because the collagen your body builds in response to the material remains even after the filler particles dissolve.
Most people schedule maintenance appointments once or twice a year to keep their results consistent. Over time, some providers find that patients need less filler at each visit because the repeated stimulation of collagen production provides a cumulative structural benefit.