Most face fillers are made of hyaluronic acid, a sugar-based molecule that already exists naturally in your skin. But hyaluronic acid is only one of several materials used in injectable fillers today. The FDA has approved five main categories: cross-linked hyaluronic acid, calcium hydroxylapatite, poly-L-lactic acid, polymethylmethacrylate, and collagen. Each one works differently, lasts a different amount of time, and is suited to different areas of the face.
Hyaluronic Acid: The Most Common Filler
Hyaluronic acid is a sugar chain found throughout your body’s connective tissue, skin, and joints. It holds water exceptionally well, which is why it keeps skin plump and hydrated in its natural state. The version used in fillers isn’t simply injected as-is, though. In liquid form, hyaluronic acid would flow away from the injection site and break down within hours. To make it useful as a filler, manufacturers chemically link the sugar chains together using a cross-linking agent, transforming the liquid into a stable gel that holds its shape under the skin.
This cross-linking process is what separates a hyaluronic acid serum you’d buy at a drugstore from the gel in a syringe at a dermatologist’s office. The degree of cross-linking determines how firm or soft the final product is. Thinner gels work for fine lines and lips, while denser gels add volume to cheeks and jawlines. Depending on where it’s injected, hyaluronic acid filler typically lasts 6 to 18 months before your body gradually breaks it down.
One major advantage of hyaluronic acid fillers is that they’re reversible. An enzyme called hyaluronidase can dissolve them by breaking apart the same sugar bonds that hold the gel together. This means that if results are uneven or a complication arises, the filler can be removed rather than waiting months for it to fade on its own. No other filler type has this kind of reliable reversal option.
Calcium Hydroxylapatite: A Mineral-Based Filler
Calcium hydroxylapatite is the same mineral found in human bones and teeth, produced synthetically for use as a filler. The product most people know by name is Radiesse, which is 30% calcium hydroxylapatite microspheres (tiny smooth beads, each 20 to 60 micrometers across) suspended in 70% carrier gel. That carrier gel is made of carboxymethyl cellulose, glycerol, and water, and it provides the initial volume after injection.
Over the first few months, your body absorbs the carrier gel. The microspheres remain and act as a scaffold, stimulating your skin to produce new collagen around them. So the filler works in two phases: immediate volume from the gel, then longer-term structural support from the collagen your body builds. Results generally last 12 to 24 months depending on the treatment area. Unlike hyaluronic acid, calcium hydroxylapatite fillers cannot be dissolved with an enzyme.
Poly-L-Lactic Acid: A Collagen Stimulator
Poly-L-lactic acid (sold as Sculptra) works fundamentally differently from traditional fillers. Rather than adding volume directly, it triggers your body to build its own collagen over time. The material is a biodegradable synthetic polymer, the same family of compounds used in dissolvable surgical stitches.
When poly-L-lactic acid particles are injected, they set off a controlled immune response. Your body recognizes the particles as foreign, sends immune cells to surround them, and in the process activates the cells that produce collagen. The particles themselves gradually dissolve, but the collagen framework they provoked stays behind. This is why results from poly-L-lactic acid develop slowly over weeks to months and why most people need a series of treatment sessions rather than a single visit. The payoff is longevity: results can last two to three years.
Polymethylmethacrylate: The Permanent Option
Polymethylmethacrylate, or PMMA, is the only FDA-approved filler material considered semi-permanent. Bellafill, the best-known PMMA filler, contains about 20% PMMA microspheres (roughly 6 million tiny beads per syringe) suspended in 80% bovine collagen gel with a small amount of lidocaine for comfort.
The bovine collagen provides immediate volume but gets absorbed by your body within about a month. The PMMA microspheres, however, do not break down. Instead, they become permanently integrated into your tissue, and your body builds new collagen fibers around and through them. Studies examining tissue at 10 years after injection found PMMA microspheres still embedded within healthy, vascularized collagen. Results last five years or longer, effectively making this a one-time treatment for many people. Because the microspheres are permanent and cannot be dissolved, this type of filler requires more careful consideration before committing.
Fat Transfer: Using Your Own Tissue
Autologous fat grafting uses your own body fat as filler material. The process has three stages: harvesting, processing, and injection. Fat is removed from a donor site (commonly the abdomen or thighs) through a small incision using a thin cannula attached to a syringe. The harvested fat is then refined, either by spinning it in a centrifuge, letting it settle by gravity, or washing and filtering it, to separate usable fat cells from blood, oil, and fluid. The purified fat is loaded into small syringes and injected into the face.
Because the filler is your own tissue, there’s no risk of allergic reaction or rejection. The tradeoff is unpredictability. Not all transferred fat cells survive in their new location, so results can be uneven, and touch-up procedures are common. Fat that does successfully establish a blood supply in the new site can last for years, potentially permanently.
How the Materials Compare
- Hyaluronic acid: 6 to 18 months, reversible with an enzyme, best for lips, under-eyes, fine lines, and cheeks
- Calcium hydroxylapatite: 12 to 24 months, not reversible, used for cheeks, jawline, and deeper facial folds
- Poly-L-lactic acid: 2 to 3 years, not reversible, works gradually through collagen stimulation, requires multiple sessions
- Polymethylmethacrylate: 5 years or longer (semi-permanent), not reversible, used for deep lines and volume loss
- Fat transfer: Variable (potentially permanent), not reversible, requires a minor harvesting procedure
What Determines Which Material Is Used
The choice of filler material depends on where it’s going, how long you want it to last, and whether reversibility matters to you. Hyaluronic acid dominates the market because it’s versatile, comes in many formulations for different facial areas, and offers the safety net of being dissolvable. For someone trying fillers for the first time, it’s the lowest-commitment option.
Calcium hydroxylapatite and poly-L-lactic acid occupy a middle ground, offering longer results with the added benefit of stimulating your body’s own collagen production. They’re often chosen for broader volume restoration rather than precise, fine-tuned corrections. PMMA is reserved for people who want lasting results and are comfortable with the permanence, since removing it requires a surgical procedure rather than a simple enzyme injection. Fat transfer appeals to people who prefer a fully natural material and don’t mind a more involved process to get it.
All FDA-approved dermal fillers are classified as Class III medical devices, the same regulatory category as heart valves and breast implants. Between 2021 and mid-2025, the FDA approved 13 new filler products or new indications, all of them containing hyaluronic acid, poly-L-lactic acid, or calcium hydroxylapatite, reflecting where the industry is concentrating its development.