In short. Choosing a filler by substance class means deciding between hyaluronic acid, calcium hydroxylapatite, poly-L-lactic acid, polynucleotides and autologous fat on the basis of behaviour, duration and reversibility. Only hyaluronic acid can be dissolved, and for every other class a disliked result is managed with time.
Key points
- The substance class decides how a filler behaves, how long it lasts and whether it can be undone.
- Hyaluronic acid is the only class that can be dissolved, with an enzyme.
- Calcium hydroxylapatite, poly-L-lactic acid and polynucleotides are managed, not reversed.
- Polynucleotides have a younger evidence base, and that belongs in the consent conversation.
- Autologous fat is a surgical procedure with a donor site and unpredictable reabsorption.
Why does the class matter more than the name?
Patients usually arrive with a product name, and the consultation usually redirects to a class. That is not evasion. The class determines how the material behaves, how long it lasts and, the decision that matters most, whether it can be undone if something goes wrong.
Hyaluronic acid: the reversible class
Hyaluronic acid is a substance the body already contains, and injected forms of it can be dissolved with an enzyme. That reversibility is unique in filler practice, and it is why this is the class most first treatments should use. Duration varies by area and formulation, generally months. Its behaviour is well characterised and its complications are the best understood of any class.
Calcium hydroxylapatite: firmer, not reversible
This class has a firmer consistency and is used where structural support is wanted, such as contour along the jaw or the chin. It cannot be dissolved. A misplaced result therefore has to be managed rather than reversed, which is a materially different position to be in if you dislike the outcome.
Poly-L-lactic acid: gradual, and a tissue response
This class works by stimulating the patient's own collagen over months rather than by adding immediate volume. The result is not visible on the day, builds gradually, and depends on the tissue response. It is not reversible, and a patient who wants to see the effect immediately will find the timeline frustrating rather than reassuring.
Polynucleotides: newer, and stated as such
This class is used for tissue quality and skin rather than for volume or contour. Its evidence base is younger than that of the older classes, and the honest position is to say so plainly rather than to present it as equivalent. Where a newer option is offered, the maturity of the evidence belongs in the consent conversation.
Autologous fat: your own tissue, placed in theatre
Fat transfer uses the patient's own tissue and introduces no foreign material, but an unpredictable proportion is reabsorbed, the result settles over months, and a donor site is added to the recovery. It is a surgical procedure rather than a clinic appointment, and it is assessed as one.
| Class | What it is used for | Reversible? | What to expect |
|---|---|---|---|
| Hyaluronic acid | Volume, contour, a first treatment | Yes, with an enzyme | Duration varies by area, generally months |
| Calcium hydroxylapatite | Structural support along the jaw or chin | No | A misplaced result is managed, not reversed |
| Poly-L-lactic acid | Gradual collagen stimulation | No | Not visible on the day, builds over months |
| Polynucleotides | Tissue quality and skin | No | An evidence base younger than the older classes |
| Autologous fat | The patient's own tissue | No | An unpredictable proportion is reabsorbed |
How is the class chosen?
The choice follows the problem and the anatomy: which layer needs support, how mobile the area is, how much volume is needed, how long a result is wanted, and how important reversibility is to the patient. A single face may be treated with more than one class in different zones, which is a plan rather than a mixture.
What should you ask before you agree?
Reversibility is the first decision, before volume, contour or duration. With hyaluronic acid the answer to a disliked result or a complication is an enzyme. With every other class the answer is management and time. That difference outranks any other comparison between products.
- Nobody has told you which class is proposed, or whether it can be dissolved.
- A non-reversible class is proposed for a first treatment without the reversibility trade-off being discussed.
- Filler is proposed for sagging, a drooping brow or laxity, none of which filler can correct.
Sources
- American Academy of Dermatology: patient information on dermal filler substances
- NICE: interventional procedures guidance on dermal fillers
- MHRA: guidance on dermal filler products and their known risks
Internal links
Frequently asked questions
Does the brand of filler matter?
The class matters more, and this site does not name brands. Within a class, products differ in consistency, how they behave in different layers and how long they last, and those differences are chosen at assessment for your anatomy rather than by preference.
How long does each class last?
It varies widely by area, class and individual response, from months to considerably longer. What does not vary is that all of them are temporary. Anyone quoting a single duration without examining you is describing an average rather than your case.
Can collagen stimulators be combined with filler?
Sometimes, and the sequence matters more than the combination. Stimulators work gradually through the tissue response, so combining them with immediate volume in the same area at the same time makes it impossible to judge what produced what. Staging is usually the better plan.
Risks & Limitations
- Vascular occlusion — filler blocking a blood vessel. This is a time-critical emergency that can cause skin loss and, rarely, vision loss.
- Nodules, lumps or delayed inflammatory reactions, which may need treatment or dissolution.
- Infection at the injection site.
- Asymmetry or over-correction. Over-treatment is harder to correct than under-treatment.
- Migration of filler away from the intended area.
- Bruising and swelling. All filler results are temporary and maintenance treatment is required.
- Filler cannot correct tissue ptosis, and a thread lift is not a facelift.
When to Seek Care
- Severe pain out of proportion to the injection, or skin turning white, grey, mottled or dusky — a vascular emergency; seek care immediately.
- Any change in vision — seek emergency care immediately.
- Fever, spreading redness, warmth or pus at an injection site.
- A hard, painful lump that is growing, or redness and swelling appearing weeks to months after treatment.
- Skin breakdown, blistering or a dusky patch over a treated area.
References & Further Reading
- American Academy of Dermatology (AAD) — injectable safety information
- American Society of Plastic Surgeons (ASPS) — dermal filler guidance
- U.S. Food and Drug Administration (FDA) — approved dermal filler products
- National Medical Products Administration (NMPA, China) — approved product status
- Chongqing West District Hospital — Plastic Surgery & Aesthetics Medical Center
This page is patient education, not medical advice, and it does not cite individual studies. Discuss your own case with a qualified clinician. To arrange an assessment at Chongqing West District Hospital, see Contact & Consultation.