RESUMEN
Objective: to evaluate the ability of different MTA thicknesses (3 and 5 mm), with or without conventional fillings, in preventing bacterial infiltration of Enterococcus faecalis in teeth with incompletely formed apices. Material and Methods: apical barriers were created which 3- and 5-mm-thick of MTA with and without conventional filling of the remaining root. 48 single-rooted human teeth were divided into four experimental groups (n=10) and two controls groups (n=8). After being mounted on a testing apparatus, Enterococcus faecalis was used as an indicator of bacterial infiltration. Inoculations were renewed every 3 days during a period of 60 days, and infiltration was assessed daily by checking the culture medium for turbidity. The results were analyzed using descriptive and analytical statistics (survival analysis). The level of significance was set at 5%. The tests were performed using the software GraphPad Prism 5.00. Results: the positive control group infiltrated within 24 hours, while the negative control group, no infiltrated. The Long-rank test did not demonstrate the existence of differences between groups. However, the Long-rank test for tendencies showed of a tendency to retard the infiltration. Conclusion: none of the MTA barriers were effective in preventing bacterial infiltration. The gutta-percha filling of the root segment in association with the 5-mm apical barrier of MTA showed a tendency to delay bacterial infiltration.