Do cell phones affect establishing electronic working length?

INTRODUCTION Patients often keep their cell phones on and nearby during root canal therapy. Cell phones release electromagnetic interference, which might disturb electronic working length measurements. The purpose of this ex vivo study was to determine the effect of a cell phone (Apple iPhone 5 [Apple, Cupertino, CA] or KP100 [LG, Seoul, Korea]) placed into direct contact with an electronic apex locator (EAL) (Dentaport Root ZX module [J Morita Corp, Tokyo, Japan] or Propex II [Dentsply Maillefer, Ballaigues, Switzerland]) on working length determination. METHODS Twenty-six human premolars without fractures or carious lesions were used; previously cleaned; and observed under magnification (×15) in order to check for the presence of only 1 apical foramen, the absence of apical resorption, an "open" apex, and accessory canals. The working length measurement was performed with a #15 K-file in the presence of 2.6% sodium hypochlorite under 4 conditions: (1) visually, under the microscope until the file tip reached the canal terminus; (2) electronically, without the cell phone in proximity; (3) electronically, with the cell phone in standby mode placed in physical contact with the EAL; and (4) electronically, with the cell phone activated by a call in the same position. The experimental model for electronic working length determination was a screw top plastic container filled with a saline solution. The measurements were repeated 3 times per canal under each condition. Scores of 1 to 3 categorized the stability of the readings as follows: (1) good stability; (2) unstable reading with minor difficulties determining the working length; and (3) major difficulties or impossible to determine the working length. A 2-way repeated measures analysis of variance (way 1: cell phone type and way 2: EAL model) was performed, and a second repeated measures analysis of variance was performed to seek a difference among the 4 working length determination conditions. RESULTS Neither the cell phone type nor the EAL affected the measurements (not significant). The electronic working length measurements gave the same results as the visual examination, and this length was not influenced by direct contact with a cell phone (not significant). It was also possible to determine the electronic working length under all the experimental conditions. CONCLUSIONS Within the limitations of the present study, it can be concluded that patients can keep their cell phones on during root canal therapy without any adverse effect on electronic working length determination.