열린 근단공을 갖는 치아에서 전자 근관장 측정 시 파일 크기의 영향

Abstract

Open apex can be caused by orthodontic treatment or external resorption of mature root as well as immature apical foramen. It has been reported that the accuracy of the electronic apex locator decreases as the size of the apical foramen increases. However, studies about the accuracy of electronic apex locator in the open apical foramen were seldom reported. The aim of this study was to evaluate the effect of file size in measuring electronic working length of teeth with open apex. 20 teeth were selected for this study. Preparation of open apex model is as folllows. 2mm of the apical end is cut with a bur, the point where the tip of #10k file is reflected on the cut root surface is set to the actual root canal length, and the root canal were shaped to the actual length with #2 Peeso Reamer. A divergent open apex was prepared by retrograde apical preparation with a .04/50 K3 Ni-Ti file inserted to the length of the cutting blade. Teeth which covered with gauze soaked with saline was inserted in plastic mold. Electronic apex locator was connected with gauze in the plastic mold. #10, #20, #30, #40, #50, #60, #70, #80 files were inserted into the root canal until the signal on the display flashed “Apex”. Rubber stop was fixed at this level and removed from root canal. Electronic working length was measured with a digital caliper. And then, mean difference between actual root canal length and electronic working length were calculated. Mean differences between actual length and electronic working length of each file were as follows; #10-1.43mm, #20-0.90mm #30-0.68mm #40-0.73mm #50-0.45mm #60-0.29mm #70-0.27mm #80-0.18mm. Working length measurement of all files were short of the apical foramen. There was a significant difference when file size increased from #40 to #50. File size have an impact in measuring working length of teeth with open apex. When the size of the apical foramen is 1.14 mm, it is more accurate to use a file of #50 size or larger when measuring the working length with electronic apex locator.