title: Critical diameter of apical foramen and of file size using the Root ZX apex locator: an in vitro study.
abstract: BACKGROUND
  An evaluation was made of the accuracy of the Root ZX apex locator (J. Morita Corp, Tokyo, Japan) in widened foramina, considering the existing controversy over this issue in the literature.
  
  
  METHODS
  Ten single-root teeth were embedded in an alginate mold. The foramina were widened from 0.6 mm to 1.0 mm. The measurements were taken with all possible file sizes ≥#10. The statistical accuracy of the Root ZX was calculated for the different diameters and for the influence of file size.
  
  
  RESULTS
  The accuracy of the Root ZX apex locator with a range of error of ±0.5 mm was 87% in an apical foramen size of 0.6 mm and 84% using files size 45 or larger in an apical foramen size of 0.7 mm. With a tolerance of ±1 mm, the accuracy was 99% in an apical foramen size of 0.6 mm, 98% using files size 45 or larger in an apical foramen size of 0.7 mm, and 95% using files size 70 or larger in an apical foramen size of 0.8 mm. In the rest, accuracy was not certain. The measurements taken with smaller files were shorter. There were no cases of overestimation of the working length.
  
  
  CONCLUSIONS
  The Root ZX apex locator was accurate for an apical size of 0.6 mm, independently of the file size; between 0.7 to 0.8 mm, we should adjust the files to the foramen, whereas above size 0.9 mm the locator is not accurate. The results show that the accuracy of this electronic apex locator is gradually lost as the foramen widens. Considering the stable conditions of in vitro studies, our findings advise caution in clinical application of the locator.
authors.affiliation: Department of Dental Pathology and Therapeutics, School of Dentistry, University of Seville, Spain.
authors.forename: Manuela
authors.initials: M
authors.lastname: Herrera
authors.forename: Camilo
authors.initials: C
authors.lastname: Ábalos
authors.forename: Cristina
authors.initials: C
authors.lastname: Lucena
authors.forename: Amparo
authors.initials: A
authors.lastname: Jiménez-Planas
authors.forename: Rafael
authors.initials: R
authors.lastname: Llamas
mesh_terms: D003762:Dental Instruments; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D004867:Equipment Design; D006801:Humans; D007180:Incisor; D009811:Odontometry / Q000295:instrumentation* / Q000379:methods / Q000706:statistics & numerical data; D012388:Root Canal Irrigants / Q000008:administration & dosage; D018915:Root Canal Preparation / Q000295:instrumentation*; D019227:Tooth Apex / Q000033:anatomy & histology*
chemical_list: D012388:Root Canal Irrigants