Accuracy and reliability of an apex locator for working length determination of lower molars. an in vitro study


  • Manoel Brito Júnior Universidade Estadulal de Montes Claros e Funorte-Faculdades Unidas Norte de Min
  • Janir Alves Soares UFVJM - Universidade Federal dos Vales do Jequitinhonha e Mucuri
  • Carla Cristina Camilo
  • Alba Moura Oliveira


apex locator, working length, lower molars.


The aim of this in vitro study was to evaluate the accuracy and reliability of an electronic apex locator (EAL) in the determination of the working length (WL) of lower molars. After appropriate endodontic access and exploration in 20 teeth, it was measured with a size 10 K-file the actual canal length (AL) of the mesio-buccal (MB) and distal (D) root canals until the apical foramen. Next, it was subtracted 1mm of the AL (WL1), taking as coronal references the vertex of the mesio-buccal and disto-buccal cusps. The teeth were embedded in an alginate model and electronic tooth length measurements were carried out using the EAL Novapex (Fórum, Israel). A 10 K-type file was inserted down the MB and D canals until EAL indicated that the file had reached the apex retreating until the mark 1. The cursors were adjusted in the same external references of WL1. The eletronic measurements were obtained by two operators, a graduate student (WL2) and a specialist (WL3). Three measurements were taken and an average recorded. The coefficient of Pearson revealed high concordance level inter-operators and intra-operators. For comparison of WL1, WL2 and WL3 the test t of Student was applied (p < 0,05). There was no statistically significant difference between all the measures for MB (p = 0,22) and D (p = 0,94) root canals. Therefore, the tested EAL was accurate and reliable in the determination of the WL of lower molars. UNITERMS: apex locator; working length; lower molars.

Author Biography

Janir Alves Soares, UFVJM - Universidade Federal dos Vales do Jequitinhonha e Mucuri

Departamento de Endodontia






Original Article