Smear Layer Removal After Varying Irrigation Times With 17% EDTA

OBJECTIVE: This study evaluated smear layer (SL) removal of rotary-instrumented root canals after varying irrigation times with 1.0 ml of 17% EDTA (REDTA, Roth International). METHODS: Forty de-identified extracted single canal teeth were instrumented with ProTaper (Dentsply Tulsa Dental) and ProFile (Dentsply) 0.04 taper rotary files. Teeth (n=10) were irrigated (30g, Max-i-Probe, Dentsply) with 1.0ml of 17% EDTA for either 60s, 30s, or 15s followed immediately by a final rinse with 3.0ml of 6% sodium hypochlorite (NaOCl). Positive controls (5 teeth) received only 6% NaOCl and negative controls (5 teeth) received 10.0ml 17% EDTA followed by the 6% NaOCl rinse. Teeth were longitudinally sectioned and prepared for scanning electron microscopy (JSM-5300, JEOL) evaluation. Representative digital images (350x, Orion, JEOL) of coronal, middle and apical sections were randomly shown to three calibrated endodontists and a consensus grade (1=no SL, 2=moderate SL and 3=heavy SL) was reached for each image. Data were analyzed using Kruskal-Wallis (alpha=0.05). RESULTS: When evaluating treatment times, significant differences were found between the coronal, middle and apical sections at 60s (p<0.001), 30s (p<0.001) and 15s (p=0.013). Significant differences were found between the 60s, 30s and 15s treatment times in the coronal (p=0.001) and middle (p<0.001) sections. CONCLUSIONS: The data from this study indicates the most effective smear layer removal was accomplished in the coronal and middle sections of root canals with a one minute 1.0 ml rinse of 17% EDTA followed by a 3.0 ml final rinse with 6% NaOCl. No irrigation time effectively removed the smear layer in the apical sections. Support provided by NNMC.