The purpose of the present study was to test the hypothesis that apical extrusion of the irrigant occurs during laser-driven irrigation in vivo. Three hundred human root canals, in 181 patients, were divided into two groups: the no lesion group (n = 140) and the lesion group (n = 160). All the root canals were enlarged using a crown down technique up to size 30-80 K-files, depending on the original condition of the root canal. For the final irrigation, the teeth were irrigated with a mixture of radiopaque contrast medium and NaOCl in solution. The solution was activated for 60 s in teeth with one canal or two canals and for 120 s in teeth with three or four canals. Radiopaque contrast medium was absent from the periapical tissues of all samples. No contrast medium was observed radiographically in the periapical tissues. The hypothesis that apical extrusion of root canal irrigants occur during laser cavitation was rejected It appears that the power of the laser used at 1 W for 1-2 min can drive the irrigation solution to the tip of the canal without harming the apical tissues.