title: Effects of Pitch Length and Heat Treatment on the Mechanical Properties of the Glide Path Preparation Instruments.
abstract: BACKGROUND
  This study aimed to compare the effects of pitch length and heat treatment on the mechanical properties of glide path establishing instruments.
  
  
  METHODS
  Prototypes of glide path preparation files (#14/.03 taper) were made to evaluate the effects of different pitch lengths and heat treatments. The files were divided into 4 groups according to the pitch length (pG and OneG) and heat treatment (pGH and OneGH). For the torsional resistance test, ultimate strength and fracture angle were measured, and the file tip was fixed at 3 different levels of 2, 4, and 6 mm from the tip (n = 10 for each level). The toughness was calculated by multiplying the ultimate strength and the fracture angle. The cyclic fatigue resistance was compared by measuring the number of cycles to fracture in a curved metal canal (n = 10). The screw-in forces were measured during instrumentation motions with a sequential increase in the pecking distance of 1 mm until the file reached the end of the simulated resin canal (n = 10).
  
  
  RESULTS
  The heat-treated groups showed lower toughness and higher cyclic fatigue resistance than the non-heat-treated groups. The short pitch groups showed significantly higher torsional strengths than the long pitch groups. The heat-treated groups had significantly lower screw-in forces than the non-heat-treated groups.
  
  
  CONCLUSIONS
  Under the limitations of this study, the torsional strength of the experimental file was reduced by heat treatment and increased by the short pitch length. Thus, a non-heat-treated file with a shorter pitch length would be favorable as a rotary glide path instrument.
authors.affiliation: Department of Conservative Dentistry, School of Dentistry, Dental Research Institute, Pusan National University, Yangsan, Korea.
authors.forename: Sang Won
authors.initials: SW
authors.lastname: Kwak
authors.affiliation: Department of Conservative Dentistry, School of Dentistry, IHBR, Kyungpook National University, Daegu, Korea.
authors.forename: Jung-Hong
authors.initials: JH
authors.lastname: Ha
authors.affiliation: Dongnam Regional Division, Korea Institute of Industrial Technology, Jinju, Korea.
authors.forename: Chan-Joo
authors.initials: CJ
authors.lastname: Lee
authors.affiliation: Endodontic Department, Hamdan Bin Mohammed College of Dental Medicine, Mohammed Bin Rashid University of Medicine and Health Sciences, Dubai, United Arab Emirates.
authors.forename: Rashid
authors.initials: R
authors.lastname: El Abed
authors.affiliation: Department of Conservative Dentistry, Faculty of Dentistry, University of Jordan, Amman, Jordan.
authors.forename: Ibrahim H
authors.initials: IH
authors.lastname: Abu-Tahun
authors.affiliation: Department of Conservative Dentistry, School of Dentistry, Dental Research Institute, Pusan National University, Yangsan, Korea. Electronic address: golddent@hotmail.com.
authors.forename: Hyeon-Cheol
authors.initials: HC
authors.lastname: Kim
mesh_terms: D003722:Dental Alloys / Q000737:chemistry*; D004867:Equipment Design; D004868:Equipment Failure; D006358:Hot Temperature; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D009532:Nickel / Q000737:chemistry; D018583:Pliability; D018915:Root Canal Preparation / Q000295:instrumentation*; D012399:Rotation; D013193:Stainless Steel / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry; D019415:Torque; D054159:Torsion, Mechanical
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium
keywords: Cyclic fatigue; glide path preparation; heat treatment; nickel-titanium rotary file; pitch length; screw-in force; torsional resistance