Effect of recapitulation on accuracy of electronically determined canal length

The accuracy of an electronic apex locator to measure canal length during instrumentation when nonrecapitulated dentin debris is present has not been evaluated. The purposes of this study were (1) to compare actual with electronic canal length before and after instrumentation, and (2) to compare the accuracy of electronic length in recapitulated and nonrecapitulated canals. Actual canal lengths of 30 mature anterior teeth were determined, teeth mounted in an in vitro system, and canal lengths determined with the electronic apex locator. Canals were step-back prepared to a size 35 file. Fifteen canals were recapitulated and the other 15 were not. Canals were dried and lengths again determined with the electronic apex locator. Data showed that for electronically determined versus actual lengths: 1) 63% were longer, 23% equal, and 13% shorter before instrumentation, 2) 30% were longer, 0% equal, and 70% shorter after instrumentation, 3) instrumentation caused a mean shortening of 0.63 mm, and 4) recapitulation of nonpatent canals was necessary to obtain length reading with the electronic apex locator.