Time-dependent effects of EDTA application on removal of smear layer in the root canal system

EDTA의 세정시간에 따른 근관 내 smear layer의 제거효과에 관한 연구 This study was to verify that the combined application of NaOCl and EDTA was more effective in removal of smear layer than the application of NaOCl alone. Furthermore it was aimed to find out the optimal time for the application of EDTA. Thirty five single rooted teeth were cleaned and shaped. NaOCl solution was used as an irrigant during instrumentation. After instrumentation, root canals of the control group were irrigated with 5 ㎖ of NaOCl for 2 minutes. 30 sec, 1 min, and 2 min group were irrigated with 5 ㎖ of 17% EDTA for 30 sec, 1 min, and 2 min respectively. Then the roots were examined with scanning electron microscopy for evaluating removal of smear layer and erosion of dentinal tubule. The results were as follows; 1. The control group: The smear layer was not removed at all. 2. The other groups: 1) Middle⅓: All groups showed almost no smear layer. And the erosion occurred more frequently as increasing irrigation time. 2) Apical⅓: The cleaning effect of 2 min group was better than the others. The results suggest that 2 min application of 17% EDTA should be adequate to remove smear layer on both apical⅓ and middle⅓.