title: Comparison of the reliability of "0.5" and "APEX" mark measurements in two frequency-based electronic apex locators.
abstract: BACKGROUND
  A measuring instrument must be both accurate and reliable. This study compared the reliability of the "0.5" and "APEX" mark measurements by using 2 impedance quotient-based electronic apex locators (EALs).
  
  
  METHODS
  One hundred four extracted human premolars were used in this study. After access preparation, the teeth were embedded in an alginate model. By using 2 EALs (Root ZX and i-Root), the tooth length was measured at the "0.5" and "APEX" marks with K-files. The file was then cemented, and the apical 3-4 mm was trimmed for the photograph under an operating microscope. The distance between the tip of the file and major foramen (MF) was measured. The intraclass correlation coefficient, the Bland-Altman plot, and box plot were used to compare the reliability.
  
  
  RESULTS
  The intraclass correlation coefficient ranged from 0.976-0.994, indicating excellent agreement in both "0.5" and "APEX" marks. The Bland-Altman plots showed that the limits of agreement (mean ± 2 standard deviations) were small enough to confirm that both marks of the 2 EALs can be used for clinical purposes. The distribution of the measurements and outliers was analyzed by using box plots, and it was found that there was no significant difference between the 2 marks.
  
  
  CONCLUSIONS
  There was no significant difference in the reliability of the "0.5" and "APEX" marks for locating the MF in both devices. Accordingly, knowing where each mark indicates is more important for determining the working length than which mark to choose.
authors.affiliation: Department of Conservative Dentistry, College of Dentistry, Yonsei University, Seoul, Korea.
authors.forename: Il-Young
authors.initials: IY
authors.lastname: Jung
authors.forename: Bum-Hee
authors.initials: BH
authors.lastname: Yoon
authors.forename: Shin-Jae
authors.initials: SJ
authors.lastname: Lee
authors.forename: Seung Jong
authors.initials: SJ
authors.lastname: Lee
mesh_terms: D003762:Dental Instruments; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D017097:Electric Impedance; D004582:Electronics, Medical / Q000295:instrumentation; D004867:Equipment Design; D006801:Humans; D009811:Odontometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D018915:Root Canal Preparation / Q000295:instrumentation*; D019227:Tooth Apex / Q000033:anatomy & histology*