Extrusion force: how hard the plunger is pushed
Quick facts
- Definition
- Force needed to push the syringe plunger and make the gel come out through the needle or cannula.
- Measurement
- Newtons (N), in a laboratory test.
- Depends on
- Gel viscosity, needle or cannula gauge and length, and speed.
- Importance
- Flow control and comfort for the injector.
- Caution
- More force does not mean more safety; product-specific data is in the package insert.
Extrusion force is the force needed to push the syringe plunger and make the gel come out through the needle or cannula. It is a property measured in the laboratory, in newtons, and depends on both the product and the device chosen. For the professional, it is the "feel in the hand" when injecting.
What does extrusion force depend on?
| Factor | Effect |
|---|---|
| Gel viscosity | More viscous gels usually require more force |
| Needle gauge | Thinner gauges increase resistance |
| Length and tip type (cannula or needle) | Longer, thinner devices offer more resistance |
| Temperature | A colder gel tends to be harder to push |
| Injection speed | The faster, the greater the force applied |
The product's cohesivity and rheology also play a part: two gels of similar viscosity can have different extrusion forces.
Why does it matter in practice?
A very high extrusion force makes fine control of flow harder, tires the hand and raises the chance of sudden movements. A force that is too low can release product more easily than desired. Choosing a balanced combination of product and device is part of preparation.
How does the professional interpret it?
Extrusion force data appears in the technical materials of some manufacturers. It is useful for comparing products, but test conditions vary, and it does not replace clinical experience. For speed and pressure, see also injection speed.
In Harmy
The app does not deal with products, syringes or injection techniques. It simulates the aesthetic effect of a volume in ml on the frontal photo.
Also known as: injection force, plunger force.
Frequently asked questions
Does a firmer gel require more extrusion force?
Generally yes, because more viscous products offer more resistance to flow. The gauge of the needle or cannula also weighs heavily, and thinner needles increase the force required.
Does extrusion force have anything to do with safety?
It affects flow control and the injector's feel. Excessive pressure is a known risk, and safety depends on technique and attention, not on a single value.