title: Comparison of Hero 642 and K3 rotary nickel-titanium files in curved canals of molars and a systematic review of the literature.
abstract: The aim of the present study was to compare the root canal preparation ability of rotary nickel-titanium (NiTi) Hero 642 and K3 files in curved mandibular or maxillary molars. A total of 40 extracted mandibular molars with two separate mesial canals, an apical width of approximately size ≤15 and a root canal curvature of 15-30° were randomly divided into two groups and instrumented using Hero 642 (n=20) or K3 files (n=20). Canal straightening, working length, transportation, cross-sectional area, minimum dentin thickness and the canal angle curvature degree were examined, and a systematic review of the literature was conducted. No statistically significant differences were observed between the two groups with regard to the mean degree of straightening, mean change in working length, mean transportation, amount of dentin removed or remaining minimum dentin thickness (P>0.05). The canal angle curvature decreased in the two groups postoperatively. The systematic review identified six studies, and overall the two files performed similarly in the majority of categories examined. Therefore, the rotary NiTi Hero 642 and K3 files demonstrated comparable shaping abilities and maintenance of working length.
authors.affiliation: Department of Operative Dentistry and Endodontics, Guanghua School and Hospital of Stomatology and Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong 510055, P.R. China.
authors.forename: Hua-Xiong
authors.initials: HX
authors.lastname: Cai
authors.affiliation: Department of Stomatology, The Second Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong 510120, P.R. China.
authors.forename: Hui-Ling
authors.initials: HL
authors.lastname: Cheng
authors.affiliation: Department of Stomatology, Eighth People's Hospital of Guangzhou, Guangzhou, Guangdong 510060, P.R. China.
authors.forename: Jie-Wen
authors.initials: JW
authors.lastname: Song
authors.affiliation: Department of Operative Dentistry and Endodontics, Guanghua School and Hospital of Stomatology and Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong 510055, P.R. China.
authors.forename: Su-Ya
authors.initials: SY
authors.lastname: Chen
keywords: Hero 642 files; K3 files; canal curvature; canal strengthening; root canal preparation