title: Evaluation of diagnostic accuracy and dimensional measurements by using CBCT in mandibular first molars.
abstract: BACKGROUND
  This study aimed to assess the diagnostic accuracy of cone beam computed tomography (CBCT) and quantitatively evaluate the morphology of mandibular first molars using CBCT.
  
  
  METHODS
  Twenty-four double-rooted mandibular first molars were evaluated by NewTom VGi CBCT. The distance from the furcation and apex to the cementoenamel junction (CEJ), diameter and thickness of canal walls, the buccolingual (BL) to mesiodistal (MD) ratio (ΔD), prevalence of oval canals at different sections and taper of the canals were all determined. In order to assess the diagnostic accuracy of CBCT, distance from the furcation and apex to the CEJ and thickness of canal walls at the CEJ and apex were compared with the gold standard values (caliper and stereomicroscope). Statistical analyses were carried out using intraclass correlation coefficient (ICC), paired t-test and repeated measures ANOVA.
  
  
  RESULTS
  A high correlation existed between the CBCT and gold standard measurements (P<0.001). In dimensional measurements, length of mesial root was higher than the distal root and lingual furcation was farther from the CEJ than the buccal furcation (P<0.001). An important finding of this study was the mesiodistal taper of the mesiobuccal (MB) and mesiolingual (ML) canals; which was equal to 0.02.
  
  
  CONCLUSIONS
  CBCT has acceptable diagnostic accuracy for measurement of canal wall thickness. Cleaning and shaping of the canals should be performed based on the unique anatomy of the respective canal; which necessitates the use of advanced imaging techniques for thorough assessment of root canal anatomy in a clinical setting.
  
  
  BACKGROUND
  Permanent mandibular first molar, accuracy, cone-beam computed tomography, dimensional measurement.
authors: Iranian Center for Endodontic Research, Research Instituteof Dental Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors: Saeed
authors: S
authors: Asgary
authors: Department of Oral and Maxillofacial Radiology, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors: Sima
authors: S
authors: Nikneshan
authors: Iranian Center for Endodontic Research, Research Instituteof Dental Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Department of Basic Sciences, School of Rehabilitation Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors: Alireza
authors: A
authors: Akbarzadeh-Bagheban
authors: Dental Research Center, Research Institute of Dental Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors: Naghmeh
authors: N
authors: Emadi