Scanning electron microscopy of root canal walls after removing the smear layer

The purpose of this study was to investigate ultrastructurally the effect of smear layer removal by applying different root canal irrigances: 3% HO2, 4% NaOCl and 15% Na-EDTA (in combination with 3% HO2, 4% NaOCl) and establish the appearance of root canal dentine surface after treatment with 15% Na-EDTA for different time periods(1 min and 5 min) using additional irrigant 3% HOor 4% NaOCl. 22 22 Teeth with single and double canals extracted for orthodontic reasons, were used in this study. After instrumentation, coronal and apical parts were removed. Middle parts were cut longitudinally into two equal segments. The specimens were grouped and treated: with HO2, NaOCl, and with combination of Na-EDTA+ HO2 and Na-EDTA+NaOCl where the irrigation with 2 Na-EDTA lasted 1 or 5 minutes. Control segments were enlarged and irrigated with distillate water to obtain the smear layer. The results obtained showed that irrigation with HOand NaOCl did 22 not remove the smear layer, one-minute application of 15% Na-EDTA followed by 4% NaOCl showed that the smear layer was completely removed. Using of 3% HOafter Na-EDTA over the same period of time obtained 22 less "clear" surfaces. Five-minute application of Na-EDTA caused excessive peritubular and intertubular dentinal erosion. It is concluded that for effective removal of smear layer with Na- EDTA, this procedure should not last longer than 1 minute and should be followed by NaOCl