The Precision of Electronic Apex Locators in Working Length Determination: A Systematic Review and Meta-analysis of the Literature

J Endod. 2015 Nov;41(11):1818-23. doi: 10.1016/j.joen.2015.08.012. Epub 2015 Sep 26.


Introduction: This study aimed to evaluate the precision of electronic apex locators (EALs) in locating the apical constriction (AC) during a root canal treatment compared with a histologic evaluation of the AC as well as the effects of possible influencing factors by means of a systematic review of the literature and meta-analysis.

Methods: A systematic search of the literature was performed to identify studies that histologically evaluated the precision of EALs in human teeth. The identified studies were subject to strict inclusion criteria followed by data extraction and meta-analysis.

Results: From 247 articles, 10 articles met the inclusion criteria, with a total of 1105 EAL measurements performed by 4 types of EALs: Root ZX (J Morita, Tokyo, Japan), Justy II (Hager & Werken GmbH & Co, Duisburg, Germany), Endy 5000 (Loser Co, Leverkusen, Germany), and Endox (Lysis Co, Milan, Italy). Root ZX, Justy II, and Endy 5000 were found to be significantly more accurate than Endox in determining the distance between the file tip and the apical constriction (P < .05). The longest mean distance was measured by Endox (1.35 ± 0.41 mm), and the shortest mean distance was measured by Justy II (0.25 ± 0.17 mm, P < .05). The mean distance measured by Root ZX and Justy II in the presence of hydrogen peroxide was shorter compared with the mean distance measured by them in the presence of sodium hypochlorite (P < .05). The pulp status (vital or necrotic) had no significant effect on the precision of the EALs.

Conclusions: The precision of electronic working length measurement depends on the device used and the type of irrigation and is not influenced by the status of the pulp tissue.

Keywords: Apical constriction; electronic apex locators; root canals; working length.

Publication types

  • Evaluation Study
  • Meta-Analysis
  • Review
  • Systematic Review

MeSH terms

  • Dental Instruments*
  • Dental Pulp Cavity / anatomy & histology*
  • Dental Pulp Cavity / diagnostic imaging*
  • Electrical Equipment and Supplies*
  • Humans
  • Root Canal Preparation / instrumentation*
  • Root Canal Preparation / methods*