Effect of three NiTi files on transportation of the apical foramen

Aim: To compare landed and nonlanded rotary file overinstrumentation on transportation of the apical foramen in the curved canals of extracted teeth. Methodology: Severely curved molar root canals (n = 45) were distributed into three equal groups (n = 15) according to angle (mean 54°) and radius of curvature (mean 5 mm). Canals were overinstrumented 0.5 mm beyond the foramen to a size 35 master apical file using landed (ProFile ISO), nonlanded (ProFile Vortex) or nonlanded, reduced shape memory (Vortex Blue) files. Post-instrumentation images of the apical foramen were compared with pre-instrumentation control images for differences in area, circularity and ratio of Feret's diameters. Groups were compared using anova or Kruskal-Wallis tests with significance of P < 0.05. Results: There were no differences between pre-treatment groups in the parameters tested. All groups demonstrated alterations in the geometry of the apical foramen. There were no significant differences between ProFile ISO, ProFile Vortex or Vortex Blue in area, circularity and ratio of Feret's diameters. Conclusions: Landed, nonlanded and nonlanded reduced shape memory files all produced transportation of the apical foramen when overinstrumented by 0.5 mm in severely curved canals. There was no difference between these file systems with regard to the degree of this effect.