The use of ultrasound and an EDTA‐urea peroxide compound in the cleansing of root canals. An SEM study*

Thirty‐two human teeth with constricted root canals were prepared using an EDTA‐urea peroxide compound as an aid to root canal instrumentation. A final irrigation of 3 per cent sodium hypochlorite with up to five minutes of indirect ultrasound was not sufficient to remove the debris and smear layer from the canal wall when viewed under the scanning electron microscope. It was suggested that the wax‐like smear layer could have clinical benefits and required further investigation.