Abstract: PURPOSE: To investigate the effect of canal curvatures on the accuracy of 3 electronic apex locators (EAL) in vitro. METHODS: Alginate and 123 canals were used to mimic the situation in vitro. Three kinds of electronic apex locators including Raypex5?, PropexⅡ? and Rider? were applied to determine the length of the canals divided into 3 groups including straight (<5°), middle (>10°,<20°) and severe (>20°）according to the root canal curvatures. Experimental measurements and the distances (IF value) between experimental and ideal actual measurements under the same measurement environment were recorded. Paired sample t test was applied to analyze the results by using SPSS11.5 software package. RESULTS: The results showed that with the allowance of ±0.5 mm, the accuracy ratios of straight canal, moderate and severe curvature canal were 84.6%, 81.6%, 87.5% for Raypex?5,76.9%,89.8%, 91.7% for PropexⅡ?, and 92.3%, 89.8%, 87.5% for Rider?, respectively. There was no significant difference in the accuracy between the EALs regarding three degrees of root canal curvatures. CONCLUSIONS: The curvatures of the root canals have no influence on the accuracy of the EALs, though the difference exists in the accuracy rate among the EALs.

Key words: Electronic apex locator, Root canal curvature, Working length