Traditionally dermal fillers have been injected using needles. Filler comes pre-packaged with needles which they recommend for use with their product. However, using a cannula has many advantages over the use of needles. The main reason is that a blunt tipped cannula reduces the likelihood of piercing blood vessels, especially arteries. As we know, injecting filler into an artery or vein can have disastrous consequences including, stroke, heart attack, necrosis of the skin or death. 

The first use of cannulas was in the use of fat grafting and they are available in 18-30 gauge and in lengths from 1-2inches. The use of a cannula takes practice, as the cannula requires additional force to work through the tissue, unlike a needle that requires less force due to the sharp tip of the needles ability to pierce through this tissue more easily. 

When a needle is used the sharp tip of the needle penetrates the skin and down to the depth where the filler is injected. A cannula on the other hand has a blunt tip and cannot pierce the skin. A needle is required to make an entry point for the cannula, the blunt tipped cannula can re-enter the same entry point to pass through the skin into the subcutaneous layer. 

Needles can cause significant bruising, swelling or worse, can cause serious complications via intravascular injection. Cannulas are less likely to pass into a vein or artery and therefore cause less bruising and swelling and can avoid intravascular injection. Instead the blunt tip of the cannula pushes veins or arteries aside as they are passed through the tissue. The practitioner is able to feel the resistance of the cannula through the tissue structures, allowing them to make a decision of how much pressure to apply and when as well as guide the cannula in the direction they want. Cannulas are also longer than needles and can therefore reach more areas, with fewer entry points into the skin. 

Cannulas have a hollow bore, just like needles, allowing the filler to pass through into the tissue. A silicone coating and a dome shaped tip design eases their insertion; manoeuvrability is easier as silicone coated cannulas reduce drag during injection. An entry port needle of the same size as the cannula is recommended.