Abstract:

Passive ultrasonic irrigation(PUI) is a favorable technique to remove bacteria, hard tissue debris, and smear layer in the root canals, such as lateral canals, isthmus and irregularities. PUI causes less extrusion and enhances the density of the obturation. Factors such as instruments, techniques, and shape of the root canal systems affect PUI efficiency. The oscillating ultrasonic tips induce powerful acoustic microstreaming and cavitation, which can produce shear stresses along the root canal wall and remove debris and bacteria. Enhancing the frequency and intensity of ultrasonic device or reducing the radius of the ultrasonic tips can enhance acoustic microstreaming. A smooth wire can be as effective as a cutting K-file as the ultrasonic tip. Nickel–titanium tips cause significantly less ledging compared with stainless steel files. Irrigation with sodium hypochlorite is effective. Cleaning efficiency ranging from 1% to 5.25% has a positive correlation with concentration, but does not exhibit statistical difference. Solution pH and temperature have no significant effect on cleaning efficacy. PUI with a pulsation pattern is more effective in removing dentin debris than a continuous oscillation. Bigger taper and smaller curvature can achieve better efficacy of dentine debris removal.

Key words: root canal preparation, passive ultrasonic irrigation, irrigant, efficiency