espanolAntecedentes: La tecnica de obturacion de conductos radiculares denominada “condensacion hibrida-mixta”, combina las ventajas de la tecnica lateral (en frio) con la tecnica termoplastificada (con calor). Hasta el momento, su efectividad de sellado no ha sido estudiada Proposito: Evaluar la capacidad de sellado de conductos radiculares obturados con tecnicas de: condensacion lateral, condensacion vertical, cono unico, con portador-Guttacore® y condensacion hibrida-mixta. Metodos: 50 dientes premolares extraidos por indicacion ortodontica y preparados con lima Primary de WaveOne® fueron distribuidos en 5 grupos y obturados con: cono unico no estandarizado Primary de WaveOne®, condensacion lateral utilizando conos de gutapercha al 2 %, obturadores calibre 30 Gutacore®, condensacion vertical con cono Primary de WaveOne® e inyeccion de gutapercha tipo alfa del sistema Beefill®; condensacion hibrida-mixta, modificando la condensacion lateral con calor e inyectando gutapercha tipo alfa del Beefill®. Enterococcus faecalis fue inoculado por la porcion coronal. Se determino microfiltracion con el cambio de color y turbidez en el caldo de cultivo con rojo de fenol. Se incubaron a 37oC por 12 semanas. Los especimenes fueron observados por microscopia electronica de barrido. Resultados: 11 especimenes (22 %) presentaron filtracion. El 46 % de los especimenes con cono unico, el 30 % con Gutacore®, el 20 % con condensacion lateral, el 10 % con la tecnica de condensacion vertical y ninguno con condensacion hibrida-mixta. Conclusion: La tecnica de condensacion hibrida-mixta mostro ser la mas eficiente para cumplir con el objetivo de un sellado adecuado y prevenir la contaminacion microbiana de los conductos en el tratamiento endodontico. EnglishBackground: The root canal filling technique named Hybrid-Mixed Condensation, combines the advantages of cold lateral and warm vertical condensation. The ability of avoiding microbial microleakage has not been proven. Purpose: To evaluate the differences of microbial microleakage using Enterococcus faecalis, in canals obturated with five different techniques: lateral, warm vertical, WaveOne® single cone, Guttacore®, and Hybrid-mixed condensation. Methods: 50 single-rooted human premolars extracted for orthodontic reasons were biomechanical prepared with primary file of WaveOne® system. Teeth were divided into 5 groups using different obturation techniques: single cone with WaveOne® Primary, lateral condensation using 2 % gutta-percha cones, Guttacore® 30, warm vertical condensation using down packing in a WaveOne® Primary cone and backfill with alpha gutapercha of Beefill®, and the hybrid mixed condensation modifying the lateral condensation with heat and a backfill using Beefill®. Enterococcus faecalis was inoculated in the coronal third and apices were immersed in brain heart infusion broth with phenol red incubated at 37 °C for 12 weeks. Microfiltration was determined with color change and turbidity of the medium. Specimens were observed by scanning electron microscopy. Results: Only 11 teeth (22 %) were positive for leakage. 46 % with single cone, 30 % with Guttacore®, 20 % with lateral condensation, 10 % with warm vertical condensation and no microleakage was found for Hybrid-Mixed Technique over the period of 12 weeks of study. Conclusion: Hybrid Mixed Technique showed to be the most efficient technique to get three-dimensional seal and prevent microbial contamination of canals in the endodontic therapy.