El proposito de esta investigacion fue evaluar el grado de desadaptacion apical que sufre la obturacion endodontica cuando se recorta para el perno inmediatamente o siete dias despues, por medio del desarrollo de un modelo experimental empleando bacterias como marcador de la microfiltracion apical. Se evaluaron 97 cortes obtenidos de 30 dientes uniradiculares y distribuidos en tres grupos: endodoncia sin recorte (Grupo A), endodoncia recortada inmediatamente (Grupo B) y endodoncia recortada siete dias despues (Grupo C), los dientes fueron sumergidos en su tercio apical en un cultivo puro de Enterococo faecalis y alli se dejaron siete dias, se descalcificaron y luego se cortaron transversalmente a 1 mm, 2mm, 3mm y 4mm del apice, tomando cortes de 2 mm de espesor, se les aplico gram histologico como tincion y se evaluo la presencia y el grado de microfiltracion bacteriana apical. Se encontro que no hubo diferencias significativas en la microfiltracion bacteriana apical entre el grupo de recorte inme¬diato (B) y el grupo de recorte siete dias despues (C). Se encontro tambien filtracion en el 96.6% de los cortes analizados para el grupo A o de endodoncia intacta, que se debio probablemente al corto tiempo entre la obturacion endodontica y la colocacion en el cultivo que no permitio adecuado fraguado del cemento. ABSTRACT The purpose of this study was to evaluate how the timing of post preparation after endodontic treatment affects the apical seal. A model which consisted of submerging the apical third of teeth in an Enterococcus faecalis culture media during seven days was used in order to identify said microorganism as a marker for detecting apical microleakage. Ninety seven sections of teeth which had received endodontic treatment were evaluated in three groups: Group A- Teeth which were not prepared; Group B- Teeth prepared immediately after treatment; Group C- Teeth prepared seven days after treatment. No significant differences were observed between Groups Band C. However, leakage was observed in 96.6% of sections evaluated in Group A. This was probably due to the short time span between endodontic treatment and the moment in which the teeth were placed in the media which did not allow for the cement to set properly.