A SEM study of canal cleanliness after a new nickel-titanium rotary instrumentation technique

The purpose of this in vitro study was to evaluate the degree of smear layer removal after root canal preparation with TF(®) instruments, combined with two different irrigating solutions.For the present study twenty-two freshly extracted human roots were selected. All teeth had been extracted for periodontal purpose. Crown were cut off with a separating disk, so all roots were approximately 10-12 mm long.After having chosen the two control roots, the remaining ones were randomly divided into two groups each containing 10 roots. The two experimental groups were prepared as follows.A crown-down instrumentation technique was used, following TF(®) manufacturer's instructions.Irrigation of Group A consisted of 2 ml of solution: 6% sodium hypochlorite (Chlor-Extra(®), Vistadental Racine, Mi, USA) after each instrument followed at the end by a 17% EDTA minute (Smear Clear(®), SybronEndo, Orange, Ca) irrigation for 1 min. Both irrigants contain tensioactive agents.Group B specimens were irrigated with 2 ml of sterile saline solutions after each instrument. Two control roots were not instrumented and irrigated. Teeth were then examined by scanning electron microscopy.Values obtained were tabulated and statistical analyses were carried out using a non parametric tests.RESULTS SHOWS SIGNIFICANT DIFFERENCES IN THE MEAN SCORE BETWEEN THE TWO GROUPS: most experimental group A canals showed clean or minimal debris in the observed areas, especially in the coronal and middle thirds.