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J Dent. 2015 May;43(5):597-604. doi: 10.1016/j.jdent.2015.01.001. Epub 2015 Jan 13.

Efficacy of 3D conforming nickel titanium rotary instruments in eliminating canal wall bacteria from oval-shaped root canals.

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Discipline of Endodontics, Department of Dentistry, Federal University of Santa Catarina, Florianópolis, Santa Catarina, Brazil.
College of Dental Medicine, Georgia Regents University, Augusta, GA, USA.
State Key Laboratory of Military Stomatology, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an, China.
College of Dental Medicine, Georgia Regents University, Augusta, GA, USA. Electronic address:



To evaluate the effectiveness of TRUShape® 3D Conforming Files, compared with Twisted Files, in reducing bacteria load from root canal walls, in the presence or absence of irrigant agitation.


Extracted human premolars with single oval-shaped canals were infected with Enterococcus faecalis. Teeth in Group I (N=10; NaOCl and QMix® 2in1 as respective initial and final irrigants) were subdivided into 4 subgroups: (A) TRUShape® instrumentation without irrigant activation; (B) TRUShape® instrumentation with sonic irrigant agitation; (C) Twisted Files without irrigant agitation; (D) Twisted Files with sonic irrigant agitation. To remove confounding factor (antimicrobial irrigants), teeth in Group II (N=10) were irrigated with sterile saline, using the same subgroup designations. Specimens before and after chemomechanical débridement were cultured for quantification of colony-forming units (CFUs). Data from each group were analyzed separately using two-factor ANOVA and Holm-Sidak multiple comparison (α=0.05). Canal wall bacteria were qualitatively examined using scanning electron microscopy (SEM) and light microscopy of Taylor-modified Brown and Brenn-stained demineralised sections.


CFUs from subgroups in Group I were not significantly different (P=0.935). For Group II, both file type (P<0.001) and irrigant agitation (P<0.001) significantly affected log-reduction in CFU concentrations. The interaction of these two factors was not significant (P=0.601). Although SEM showed reduced canal wall bacteria, bacteria were present within dentinal tubules after rotary instrumentation, as revealed by light microscopy of longitudinal root sections.


TRUShape® files removed significantly more canal wall bacteria than Twisted Files when used without an antibacterial irrigant; the latter is required to decontaminate dentinal tubules.


Root canal disinfection should not be focused only on a mechanistic approach. Rather, the rational choice of a rotary instrumentation system should be combined with the use of well-tested antimicrobial irrigants and delivery/agitation techniques to establish a clinically realistic chemomechanical débridement protocol.


Canal conforming; Dentine conservation; E. faecalis; Nickel titanium; Rotary instrumentation; Sonic agitation

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