title: [A study on the accuracy of electronic root canal length measurement and its influential factors].
abstract: OBJECTIVE
  To study the accuracy of JUSTY-II electronic apex locator and the influential factors on the accuracy of root canal working length measurement.
  
  
  METHODS
  148 teeth, including 71 teeth with pulpitis, 46 with necrotic pulp and 31 with apical periodontitis, were divided into two groups in random. The accuracy of electronic root canal working length measurement group was compared with that of the manual measurement group by Chi(2) test. The influence of clinical types, root canal in dry or moisture conditions and root canal preparation on the accuracy of root canal working length measurement was analyzed.
  
  
  RESULTS
  The accuracy of electronic apex locator was 87.84%, while it was 43.24% in manual measurement, the difference was significant (P<0.01). The accuracy in the group of apical periodontitis was significantly lower than that of the other groups (P<0.05). Root canal in dry or moisture conditions had no effect on the accuracy of root canal length measurement, but root canal preparation could decrease the accuracy of measurement (P<0.05).
  
  
  CONCLUSIONS
  Electronic apex locator is an accurate and convenient device in measurement of root canal working length. Apical periodontitis and root canal preparation can decrease the accuracy of measurement.
authors: Department of Stomatology, Shanghai Traditional Chinese Medicine and Western Integrated Hospital, Shanghai 200082, China. swzlym@online.sh.cn
authors: Yu-miao
authors: YM
authors: Lu
authors: Jia-nan
authors: JN
authors: Qin
authors: De-jing
authors: DJ
authors: Cao