There no continuous physical contact between the canal’s wall and the tip during use. The tip is passive, with no blade but smooth structure and studies show that dentin removal is not significant. It has a transducer role only, making the ultrasounds propagate in the liquid, close to the apex. The clinical effect is based on a physical phenomenon due to the propagation of ultrasounds inside a liquid, creating cavitation and acoustic streaming. This is not the case with sonic activators based on a different principle and acting as mecanical agitators (electrical mixer). The risk of instrument fracture is very limited since the power is set for the tip whish has been specifically designed for this use, compared to multi-fonctions ultrasounds generators where the power has to be manually adjusted to the tip used with a risk of over-power.