Biostimulators vs. Hyaluronic Acid Fillers: What’s the Difference and Which is Right for You?
5 minute read
In the world of aesthetic injectables, not all fillers are created equal—and that’s a good thing. Whether you're looking to restore volume, enhance features, or smooth out wrinkles, your injector has a wide range of tools at their disposal. Two major categories dominate the conversation: biostimulators like Sculptra and Radiesse, and hyaluronic acid (HA) fillers such as Restylane, Juvederm, and RHA. But what sets them apart? Let's break it down.
The Science: Chemical Makeup
Sculptra is made from poly-L-lactic acid (PLLA), a biodegradable synthetic substance that has been used in dissolvable sutures for decades.
Radiesse contains calcium hydroxylapatite (CaHA) microspheres suspended in a water-based gel. CaHA is similar to the mineral content found in bones and teeth.
HA fillers like Restylane, Juvederm, and RHA are made from hyaluronic acid, a naturally occurring sugar molecule found in your skin and joints that helps maintain hydration and volume.
How They Work: Mechanism of Action
Sculptra and Radiesse are biostimulators, meaning they stimulate your body to produce its own collagen over time. After injection, they provide an initial filling effect, but their main benefit comes from their ability to trigger a wound-healing response that rebuilds dermal structure from within.
Sculptra gradually stimulates collagen over weeks to months, with results that improve over time.
Radiesse provides an immediate lift due to its gel carrier but also promotes collagen synthesis as the CaHA microspheres break down.
HA fillers, on the other hand, work by directly adding volume and structure. They attract water molecules, plumping the skin and filling folds or hollows instantly. Over time, they are naturally metabolized by the body.
How Long Do They Last?
Sculptra: Results develop gradually and can last up to 2 years or more, especially with proper treatment series and maintenance.
Radiesse: Offers immediate results and typically lasts 12–18 months, with some collagen-stimulating effects persisting even longer.
HA Fillers:
Restylane and Juvederm fillers last 6 to 18 months, depending on the specific product and treatment area.
RHA fillers, a newer generation designed for dynamic facial movement, last 12–15 months on average.
HA Fillers: Understanding G’, Swelling Factor, and Cohesivity
Not all HA fillers are the same. Their performance depends on their rheological properties, which determine how they behave once injected:
G’ (Elasticity or Stiffness): A higher G’ means the filler is firmer and better at holding shape under pressure. These are great for lifting deeper structures—think cheeks or chin.
Swelling Factor: This refers to how much water the filler attracts after injection. Fillers with high swelling capacity add volume but may not be ideal for superficial or delicate areas.
Cohesivity: Measures how well the product holds together. More cohesive fillers are better for shaping and contouring, while less cohesive ones spread more easily and are ideal for fine lines or under-eye treatment.
For example:
Restylane Lyft and Juvederm Voluma have higher G’ and are used for structural support.
RHA 2 and 3 are formulated for dynamic areas like nasolabial folds and lips, balancing flexibility with volume.
Restylane Silk has low G’ and cohesivity, making it ideal for fine lip lines or tear troughs.
Choosing the Right Product for the Right Place
The differences in chemical makeup and rheological properties influence where and how each filler should be used:
Biostimulators are ideal for full-face rejuvenation, volume restoration in temples or midface, and long-term collagen rebuilding.
HA fillers are better for precise contouring, lip enhancement, under-eye hollowing, and treating lines and folds with immediate results.
Final Thoughts
There’s no one-size-fits-all filler—nor should there be. The beauty of today’s injectables lies in their versatility. Your injector will evaluate your goals, facial anatomy, and lifestyle to curate the right combination of products for you. Whether it’s the long-term collagen stimulation of Sculptra, the dual-action lift and biostimulation of Radiesse, or the instantly gratifying plump of an HA filler, you’re in expert hands.
