title: The Efficacy of FlexMaster's IntroFile, PreRaCe and Gates Glidden Drills in Straight-Line Access: A CBCT Assessment.
abstract: BACKGROUND
  An overlooked but important part of successful root canal treatment is a straight-line access (SLA). The purpose of this in vitro study was to compare the efficacy of IntroFile and PreRaCe rotary instruments with Gates Glidden (GG) drills in gaining SLA by cone-beam computed tomography (CBCT).
  
  
  METHODS
  A total of forty five extracted mandibular first molars were selected and mounted in dental like arches. Subsequently, they were randomly classified into three groups (n=15). After preparation of a standard access cavity, orifices of the mesiobuccal canal was reached and a #10 file was inserted to explore the canals until the file tip was visible at the apex. Then, preoperative CBCT images were taken. SLA was gained in three groups; group 1, FlexMaster's IntroFile (FM); group 2, PreRaCe (RC) and group 3, GG. Again, the first binding file at the working length (WL) was placed in the canal and postoperative CBCT images in similar positions were taken. The pre/post operative morphology of the canal was evaluated for changes. Data was analyzed using the one-way ANOVA and post-hoc Bonferroni analysis.
  
  
  RESULTS
  The average amount of reduction in coronal canal curvature in FM, RC and GG groups was 2.43±1.79, 3.17±2.05 and 8.7±3.45, respectively. This descending trend was statistically significant. The difference between pre/post SLA changes in FM and RC groups was significant compared to GG group, while there were no significant differences between RC and FM.
  
  
  CONCLUSIONS
  GG drills produced extraordinary results in reducing coronal curvature of the canal and achieving SLA. They are also more effective than nickel-titanium (NiTi) rotary instruments in canals with coronal curvature.
authors.affiliation: Department of Endodontics, Dental School, Zahedan University of Medical Sciences, Zahedan, Iran.
authors.forename: Narges
authors.initials: N
authors.lastname: Farhad Mollashahi
authors.affiliation: Department of Oral and Maxillofacial Radiology, Dental School, Zahedan University of Medical Sciences, Zahedan, Iran.
authors.forename: Mahdi
authors.initials: M
authors.lastname: Sohrabi
authors.affiliation: Department of Oral Medicine, Dental School, Zahedan University of Medical Sciences, Zahedan, Iran.
authors.forename: Leila
authors.initials: L
authors.lastname: Farhad Mollashahi
authors.affiliation: Department of Oral and Maxillofacial Radiology, Dental School, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Mojdeh
authors.initials: M
authors.lastname: Mehdizadeh
keywords: Access Cavity; CBCT; Cone-Beam Computed Tomography; Engine-Driven Instruments; Radicular Access; Root Canal Preparation; Rotary Systems; Straight-Line Access