Aesthetic medicine
Tissue stimulators or fillers, how they differ
Both groups of preparations are injected and both are sometimes proposed for the same changes. They work on two different principles, though, and that decides when each one makes sense.
Published 19 August 2020. Last reviewed 26 September 2026.
Category
Aesthetic medicine
Applies to treatments
Treatment performed by
Doctor
The difference in one sentence
A filler replaces volume where it has been lost, and does so immediately after injection. A stimulator works indirectly: it prompts the skin to produce its own collagen, and the change appears over the following weeks and months.
This distinction matters at the assessment stage. If the problem is a loss of volume in a specific spot, a filler is often the right tool. If the problem is a decline in skin quality over a larger area, a stimulator is considered. Some preparations combine both properties.
Tissue stimulators, how they work
Tissue stimulators are preparations used to rebuild the structure of the skin. They prompt the production of building blocks, above all collagen and elastin. The aim of the therapy is to improve skin firmness and structure. The extent of the change depends on the preparation, the number of treatments, age and the individual response of the tissues.
Poly-L-lactic acid
A preparation in the form of a suspension, injected under the skin. It also allows tissue deficits to be replaced, which is why it counts among the biostimulators with a stronger structural effect.
Platelet-rich plasma
Platelet-rich plasma is obtained from the patient's venous blood, so it is an autologous preparation, meaning one that comes from her own body. Its action comes from growth factors released by platelets, which stimulate regenerative processes in the dermis and the subcutaneous tissue.
The body's own material does not cause an allergic reaction to the preparation, which does not mean the treatment is free of risk. An injection carries a risk of haematoma, swelling, pain and infection, and the doctor assesses contraindications before blood is drawn.
Calcium hydroxylapatite
Calcium hydroxylapatite stimulates collagen synthesis in the skin and at the same time has a gel-like consistency, which is why it is sometimes used to work on the facial contour and to fill wrinkles. It therefore combines the properties of a stimulator and a filler.
Fillers, how they work
Fillers are substances injected to fill wrinkles or improve the contours of the face. The most commonly used biodegradable filler is hyaluronic acid, a natural component of the human body whose amount decreases with age.
The filling effect is visible immediately after the treatment. The preparation degrades gradually, so maintaining the result requires repeating the treatment, and the interval depends on the preparation and the area.
Which preparation and when
There is no single preparation that is right for every patient. A filler answers a loss of volume, a stimulator a decline in skin quality. In some cases the doctor proposes a staged or combined approach, but that is decided by an assessment of the tissues, not by a scheme adopted in advance.
All the preparations listed are injected, so the assessment is carried out by a doctor. It covers the medical history, contraindications, previous treatments in the area and a discussion of possible complications.
What the research says
Reviews behind the distinction between filling and stimulation and the description of the individual preparations.
A review of the uses and safety of injectable fillers. The authors contrast hyaluronic acid, which provides volume immediately after injection, with preparations that work by stimulating collagen production, such as poly-L-lactic acid. They also discuss complications, from swelling and pain to serious vascular complications. Hence the statement in this entry that a doctor carries out the qualification for each of these preparations.
Liu J, Gao M, Hu H, Pang H, Liu Y, Zhang P. Facial injectable fillers in aesthetic medicine: clinical applications and safety strategies. Medical Science Monitor. 2025;31:e949944.
A description of the properties of poly-L-lactic acid. The microparticles of the preparation trigger a mild, clinically invisible inflammatory reaction in the tissue that stimulates collagen deposition, and volume is restored as a result of this remodelling. This is the basis for describing poly-L-lactic acid as a stimulator with a structural effect.
Fitzgerald R, Bass LM, Goldberg DJ, Graivier MH, Lorenc ZP. Physiochemical characteristics of poly-L-lactic acid (PLLA). Aesthetic Surgery Journal. 2018;38(Suppl 1):S13–S17.
A review of the history, biology, mechanism of action and classification of platelet-rich plasma. The authors define it as a portion of plasma from the patient's own blood in which the platelet concentration exceeds the baseline, and list its uses in dermatology, including tissue regeneration and skin rejuvenation. This is the basis for describing plasma as an autologous preparation.
Alves R, Grimalt R. A review of platelet-rich plasma: history, biology, mechanism of action, and classification. Skin Appendage Disorders. 2018;4(1):18–24.
A review of the mechanism of action of calcium hydroxylapatite in a carrier gel. The microspheres of the preparation provide volume and at the same time form a scaffold on which skin cells produce collagen, elastin and new blood vessels. The review notes that some mechanisms are not yet fully understood. Hence the description in this entry of a preparation that combines the features of a stimulator and a filler.
van Loghem J. Calcium hydroxylapatite in regenerative aesthetics: mechanistic insights and mode of action. Aesthetic Surgery Journal. 2025;45(4):393–403.
A review of the chemical structure and tissue behaviour of the three most commonly used biodegradable fillers: hyaluronic acid, calcium hydroxylapatite and poly-L-lactic acid. The preparations differ in composition, tissue response and durability, and as biodegradable products they are gradually broken down by the body. Hence the statement in this entry that maintaining the result requires repeating the treatment, with the interval depending on the preparation.
Herrmann JL, Hoffmann RK, Ward CE, Schulman JM, Grekin RC. Biochemistry, physiology, and tissue interactions of contemporary biodegradable injectable dermal fillers. Dermatologic Surgery. 2018;44 Suppl 1:S19–S31.
About this text
Prepared by the NL Clinic team. Published 19 August 2020, reviewed 16 August 2026.
The content is for information and does not replace a consultation.
Choice of preparation after an assessment of the tissues
The choice between filling and stimulation follows from what is causing the change. The doctor establishes this during the examination.