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Aim: The present in-vitro study aimed to compare the fracture resistance of mandibular premolars, obturated after instrumentation by Self-Adjusting File (SAF), ProTaper NEXT (PTN) and WaveOne (WO).Method: Sixty extracted mandibular premolars were decoronated to obtain the root length of 15 mm. The samples were divided into 4 experimental groups: Group 1 without instrumentation (control), Group 2 instrumented with SAF, Group 3 with PTN (X1 and X2) and Group 4 with WO (primary). Following instrumentation, the samples were obturated by cold lateral compaction technique using gutta-percha and AH Plus sealer. A week later, after the sealer was completely set, a vertical load was applied to the specimen's canal until fracture. Statistical analysis was performed.Results: The mean fracture load exhibited significant difference (p < 0.01) (One-way ANAOVA) between the groups. The Multiple Tukey post hoc tests revealed, the fracture resistance by group 1 showed no statistical difference when compared to group 2 and group 3 (p > 0.05), but a significant difference with group 4 (p < 0.01). Group 2 (SAF) presented a significantly higher fracture resistance when individually compared to group 3 and 4 (PTN and WO) (p < 0.01). Conclusion: Teeth instrumented by SAF exhibited a better fracture resistance.

Aim: The present in-vitro study aimed to compare the fracture resistance of mandibular premolars, obturated after instrumentation by Self-Adjusting File (SAF), ProTaper NEXT (PTN) and WaveOne (WO).Method: Sixty extracted mandibular premolars were decoronated to obtain the root length of 15 mm. The samples were divided into 4 experimental groups: Group 1 without instrumentation (control), Group 2 instrumented with SAF, Group 3 with PTN (X1 and X2) and Group 4 with WO (primary). Following instrumentation, the samples were obturated by cold lateral compaction technique using gutta-percha and AH Plus sealer. A week later, after the sealer was completely set, a vertical load was applied to the specimen's canal until fracture. Statistical analysis was performed.Results: The mean fracture load exhibited significant difference (p < 0.01) (One-way ANAOVA) between the groups. The Multiple Tukey post hoc tests revealed, the fracture resistance by group 1 showed no statistical difference when compared to group 2 and group 3 (p > 0.05), but a significant difference with group 4 (p < 0.01). Group 2 (SAF) presented a significantly higher fracture resistance when individually compared to group 3 and 4 (PTN and WO) (p < 0.01). Conclusion: Teeth instrumented by SAF exhibited a better fracture resistance.

Antecedentes: El sistema ProTaper Next, cuyos instrumentos mecanizados tienen un movimiento continuo con secciones trasversales excéntricas, producen un movimiento serpenteante que podría no mantener centrado el conducto radicular. Objetivo: Evaluar la transportación y la centricidad del sistema ProTaper Next con y sin el sistema PathFile, en conductos radiculares con curvatura moderada y evaluados por medio de tomografía volumétrica de rayo de cono. Métodos: Se tomaron 67 conductos radiculares de molares superiores con curvaturas moderadas de 10-20º. Se almacenaron en formalina al 10%, se seccionaron y decoronaron, y luego se dividieron en dos grupos de estudio de acuerdo con su instrumentación: ProTaper Next con y sin PathFile. Se tomaron tomografías de rayo de cono antes y después de la instrumentación. El análisis de las imágenes se realizó con el programa OsiriX, que evaluó la centricidad y la transportación de los tercios coronal, medio y apical en sentido vestibulolingual y mesodistal, a través de la superposición de imágenes antes y después de la tomografía. Resultados: Los grupos evaluados mantuvieron la centricidad sin transportar el conducto en sentido vestíbulopalatino y mesodistal en los tres tercios, sin presentar diferencias estadísticamente significativas (p<0,05). Conclusiones: Las limas rotatorias ProTaper Next no producen pérdida de centricidad ni transportación en ninguno de los tercios durante la preparación de conductos vestibulares de molares superiores con curvaturas moderadas. La instrumentación de conductos con ProTaper Next, con o sin las limas PathFile, no influye en la centricidad y transportación del conducto.