Irrigant delivery by a syringe and needle is still widely used during root canal treatment. It seems to perform similarly to other irrigation methods in the main root canal, provided that the needle is inserted close to working length, the canal is adequately enlarged and the irrigant is delivered at a sufficient flow rate. However, additional delivery and activation methods are needed to clean and disinfect areas beyond the main root canal. Neither the entrapment of air bubbles in the apical part of the root canal ('apical vapor lock') nor the surface tension of irrigants are limiting irrigant penetration during syringe irrigation. Schlagwörter: flow, irrigation, needle, penetration, syringe