The purpose of nonsurgical endodontic therapy is to completely obturate the root canal system after cleaning, desinfection and shaping. The ideal techniques and obturation material should provide hermetic seal which prevents both coronal and apical leakage. One of the methods having more clinical relevance is bacterial penetration. The purpose of this investigation was compare the behaviour of the apical microfiltration in two root filling technique: lateral condensation and Obtura II. using a method of bacterial penetration, through the time Fifty-four single root canal were prepared chemomechanical and allocated in four groups; two experimental ando two controls 25 roots obturated with lateral condensation and 25 obturated with Obtura 11 The other roots two for positive control and two for negative control. The roots were radiographed in order lo evaluate the type of obturation, the strain used was Streptococcus salivarius, with inoculations every 48 hours along the experiment. No significant difference was found between the two experimental groups (P = 0.961) The microfiltration in days of lateral condensation was in a period of time of 23.4 +6.5 and for Obtura II 23.1 1 + 5.3 This statistical analysis shows that this investigation didn't show significant difference in the time of microfitlration between the two techiques.