title: Occurrence of Dentinal Microcracks in Severely Curved Root Canals with ProTaper Universal, WaveOne, and ProTaper Next File Systems.
abstract: BACKGROUND
  This study aims to compare the incidence of dentinal microcracks produced by the ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland), WaveOne (Dentsply Maillefer), and ProTaper Next (Dentsply Maillefer) file systems during root canal procedures in severely curved canals using a dyeing technique.
  
  
  METHODS
  Sixty extracted human molars with 25° to 40° root curvatures were divided into 3 groups of 20 canals each. ProTaper Universal, WaveOne, and ProTaper Next file systems were used for root canal procedures. Untreated root canals of 60 molars served as negative controls. After preparation, all roots were stained with 1% methylene blue for 24 hours. Roots were then sectioned at the most curved plane and 2 mm below and above the most curved plane with a low-speed saw under cold water. A stereomicroscope was used to inspect dentinal microcracks at 60× magnification, and differences between these 3 instrument groups were analyzed using the chi-square test.
  
  
  RESULTS
  The ProTaper Next system induced less complete and incomplete dentinal microcracks compared with the ProTaper Universal and WaveOne systems (P < .05), and there were no significant differences between the ProTaper Universal and WaveOne systems (P > .05). The ProTaper Universal and WaveOne systems induced significantly more complete cracks in the plane 2 mm above the most curved plane compared with either of the other 2 planes (P = .004).
  
  
  CONCLUSIONS
  The ProTaper Next system induces less dentinal microcracks during root canal procedures in severely curved root canals compared with the ProTaper Universal and WaveOne systems.
authors.affiliation: State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China; West China College and Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Shu-hui
authors.initials: SH
authors.lastname: Li
authors.affiliation: State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China; West China College and Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Lu
authors.affiliation: State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China; West China College and Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Dongzhe
authors.initials: D
authors.lastname: Song
authors.affiliation: State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China; West China College and Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Xuedong
authors.initials: X
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China; West China College and Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Qing-hua
authors.initials: QH
authors.lastname: Zheng
authors.affiliation: State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China; West China College and Hospital of Stomatology, Sichuan University, Chengdu, China. Electronic address: gaoyuan@scu.edu.cn.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China; West China College and Hospital of Stomatology, Sichuan University, Chengdu, China. Electronic address: dingminghuang@163.com.
authors.forename: Ding-ming
authors.initials: DM
authors.lastname: Huang
mesh_terms: D003762:Dental Instruments / Q000009:adverse effects*; D003786:Dental Pulp Cavity / Q000473:pathology*; D003804:Dentin / Q000473:pathology*; D006801:Humans; D003765:Models, Dental; D008963:Molar / Q000473:pathology; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods*; D013194:Staining and Labeling; D016896:Treatment Outcome
keywords: Curved root canals; dentinal cracks; microcracks; nickel-titanium instruments; root canal procedure; vertical root fracture