ELECTRONIC LENGTH MEASUREMENT USING SMALL AND LARGE FILES IN ENLARGEDCANALS

Electronic apex locators are frequently used attached to a small size endodontic file; however, the effect on the measurement of the relativ e diameters of the file and the root canal has not been clarified. In this study, the length of enlarged canals was measured using small siz e tiles and files matching the canal diameter to observe a possible di screpancy. The accuracy of electronic length control during canal prep aration with rotary files was also assessed. The root canals in 21 ext racted, single rooted teeth were accessed, and their actual length (AL ) established by passing a size 10 die just through the minor apical f oramen. The teeth were then embedded in an alginate mold. The initial canal length (IL) was measured with the Root ZX apex locator by negoti ating a size 10 file to the apical constriction. The canal was enlarge d to size 60 with rotary files while the length was continuously contr olled with the apex locator. Then, the final length measurements were obtained with a size 10 file and a size 60 file (FL-10 and FL-60, resp ectively). The average values of IL, FL-10 and FL-60 were calculated a nd compared using Repeated Measures Analysis of Variance followed by T ukey's Studentized Range test (P < 0.05). Using composite resin, the s ize 60 files were secured at the FL-60 length, the teeth were removed from the alginate mold, stained with Picroformal DI Buoin stain and th e position of the file tip was observed histomorphometrically after th e apical 4 mm of the canal was exposed by grinding the buccal aspect o f the root. The IL was 0.45 mm shorter than AL (P < 0.05). The differe nces between FL-10, FL-60 and IL were not statistically significant. H istomorphometrically, the apical constriction was absent in all the te eth, but the file tips were confined within the root. This study concl uded that the Root ZX indicated the location of an apical constriction even when the anatomic constriction was eliminated. In the enlarged c anals, length measurements obtained with small and large size files we re comparable.